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39109 Publications

Development of Machine Learning Framework for Interfacial Force Closures Based on Bubble Tracking Data

Tai, C.-K.; Lucas, D.; Bolotnov, I.

This work aims to develop data-driven modeling framework with the aid of machine learning methods and high-fidelity dataset. To gain confidence on the methodology, a bubble drag regression task using artificial dataset is conducted. Result shows FNN’s capability performing non-linear fitting. On the other hand, the sample size test would give sense on model underfitting with same amount of knowledge. Inspired by the previous task, the focus then moved on to utilize DNS bubble tracking dataset for modeling interfacial momentum exchange terms. A novel way to approach interfacial momentum exchange is proposed. Preliminary result reveals the concern of model accuracy on unseen data points. Improvement on model generalization is suggested. Also, further refinement on label formation and data processing should be taken care of. Nonetheless, the potential using high fidelity data and NN to directly model interaction between phases in bubbly flow has been shown.

Keywords: DNS; bubbly flow; drag; machine learning

  • Contribution to proceedings
    2020 ANS Virtual Winter Meeting, 16.-19.11.2020, Online, USA
  • Lecture (Conference) (Online presentation)
    2020 ANS Virtual Winter Meeting, 16.-19.11.2020, Online, USA

Permalink: https://www.hzdr.de/publications/Publ-32111
Publ.-Id: 32111


Stress-Induced Modification of Gyration Eigen-Frequencies in Stacked Double-Vortex Structures

Iurchuk, V.; Kakay, A.; Deac, A. M.

The ground state of nanoscale circular magnetic disks of certain geometric aspect ratios is a spontaneously forming stable vortex configuration with circulating in-plane magnetization and a vortex core pointing out-of-plane. Resonantly exciting the VC via either an rf magnetic field or an rf spin-polarized current yields a gyrotropic motion around its equilibrium position, characterised by a specific eigen-frequency, which depends on the material parameters and the disk geometry [1]. Such oscillations, which can be read out via periodic magnetoresistance changes, generate rf signals with high quality factors (>10000) in the sub-GHz bandwidth [2,3]. While all these features make vortex-based nano-oscillators interesting as nanoscale rf sources, the major drawback remains their low frequency tunability associated with the linear characteristics of the gyrotropic mode.
Here, we investigate the role of magnetostriction in improving the tunability of vortex nano-oscillators. Specifically, we consider a double-disk structure comprising magnetostrictive (CoFe) and non-magnetostrictive (Py) layers separated vertically by a non-magnetic spacer. We show that, when the two vortices have different eigen-frequencies and the magnetostatic coupling between them is sufficiently strong, the stress-induced magnetoelastic anisotropy can lead to the synchronized gyration of the two vortex cores (Fig. 1). The stress-induced transition from double-frequency to single-frequency dynamics is mostly controlled by the polarization of the vortices and the magnetostatic coupling strength (i.e. spacer thickness). These findings offer a frequency tunability of vortex-based oscillators via mechanical stress, which can be generated and controlled electrically, for example, using piezoelectric substrates [4].

Funding from the EU Horizon 2020 project No. 737038 (TRANSPIRE) is acknowledged.

[1] K. Yu. Guslienko, et al, J. Appl. Phys. 91, 8037 (2002).
[2] A. Dussaux, et al, Nat. Commun. 1, 1 (2010).
[3] N. Locatelli, et al, Appl. Phys. Lett. 98, 062501 (2011).
[4] M. Filianina, et al, Appl. Phys. Lett. 115, 062404 (2019).

Keywords: Magnetic vortex; Micromagnetic modelling; Magnetoelastic effect

  • Poster (Online presentation)
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual event, Virtual event

Permalink: https://www.hzdr.de/publications/Publ-32110
Publ.-Id: 32110


Synthesis, structure and magnetic properties of Sm1.2Ho0.8Fe17Нx (x = 0; 4.4)

Veselova, S. V.; Paukov, M. A.; Tereshina, I. S.; Verbetsky, V. N.; Zakharov, K. V.; Gorbunov, D.; Vasil`Ev, A. N.

Intermetallic compounds based on rare-earth metals and iron are by far the most promising materials for permanent magnets. In this work, the multicomponent compound Sm1.2Ho0.8Fe17 was prepared by induction melting. The hydride Sm1.2Ho0.8Fe17H4.4 with a high hydrogen content was obtained by direct hydrogenation of the intermetallic compound. The rhombohedral Th2Zn17-type of structure (space group R3m) is inherent to parent compound and hydride as well. The effect of hydrogenation on the magnetic properties of Sm1.2Ho0.8Fe17 was investigated. Curie temperature of the hydride Sm1.2Ho0.8Fe17H4.4 is higher than that of parent compound by ΔTC = 138 K. The hydrogen embedded in Sm1.2Но0.8Fe17 crystal lattice increases the saturation magnetization (σS) at T = 300 K, but does not significantly affect σS at Т = 4.2 K. The ferrimagnetic structure is retained in magnetic fields up to 58 T in the parent compound, while, in the hydride, there is a spin-reorientation phase transition observed at 55 T. It is found that the parameter of the intersublattice exchange interaction decreases significantly in the hydride Sm1.2Ho0.8-Fe17H4.4 (and in the nitride Sm1.2Ho0.8Fe17N2.4) which is associated with boosting of the unit-cell volume and distances between magnetic ions.

Permalink: https://www.hzdr.de/publications/Publ-32109
Publ.-Id: 32109


He⁺ Ion Irradiation Induced Sn Extrusion out of SnO Covered Tin Spheres – a Combined Computer Simulation of Defect Generation and Defect Kinetics

Tucholski, D.; Heinig, K.-H.; Möller, W.; Klingner, N.; Hlawacek, G.; Facsko, S.; Hübner, R.

Here we report on a combined computer simulation of defect generation and defect kinetics for 30 keV He⁺ ion irradiation of sub-μm-scale tin spheres. In the process to be simulated, the irradiation was performed in a Helium Ion Microscope which allows the in-situ monitoring of morphological changes of the nanospheres during He⁺ ion irradiation. Above a He⁺ fluence of ∼10¹⁷ /cm², Sn extrusions appear on the surface of the spheres. Initially, small, pyramidally facetted extrusions evolve at the equator of the tin spheres (north pole pointing to the ion source), later on each sphere becomes completely covered with tin, then turning into facetted single crystals. No Sn extrusions were observed for tin spheres with diameters smaller than ∼100nm. Transmission electron microscopy and Auger electron spectroscopy investigations show that the tin spheres are covered with a few-nm-thick SnO skin and that the extrusions are single crystals.
For the computer simulations a model was developed which assumes that He⁺ ions generate interstitials ISn and vacancies VSn in the body-centered tetragonal lattice of tin. Due to the SnO skin, the ISn and VSn are confined to the tin sphere. A coherent Sn-SnO interface with a strong Sn-SnO interaction prevents ISn and VSn annihilation and void formation here. The projected range of 30 keV He⁺ ions is smaller than the diameter of the sub-μm spheres, the He accumulates and partly fills the VSn. Thus, the “pressure” of ISn increases steadily. Simultaneously, He⁺ ion erosion creates openings in the SnO skin. The sputter coefficient increases with the angle of incidence, thus openings in the SnO skin form at the equator regions first. Once the tin interstitials find such an opening in the SnO skin, they can escape from the interior of the Sn sphere and form an epitaxial, regular Sn lattice outside. Due to the high Sn-SnO bond strength the extruded tin wets the outer SnO surface.
The defect generation at He⁺ ion irradiation was simulated with TRI3DYN [1], a 3D program calculating atomic displacements in the binary collision approximation. The reaction-diffusion behavior of the ISn and VSn as well as their clustering into voids and growth to extrusions were simulated with a 3D kinetic lattice Monte Carlo program [2] using an RGL potential for tin. The simulated reaction pathway of the morphology agrees very well with the sequence of HIM images taken during He⁺ ion irradiation. A quantitative comparison of the extruded material with simulations provides conclusions on the defect kinetics under ion irradiation.

[1] Möller, Nucl. Instr. Meth. B 322 (2014) 23
[2] Strobel et al., Phys. Rev. B 64 (2001) 245422

Related publications

  • Lecture (Conference) (Online presentation)
    2021 Spring Meeting of the European Materials Research Society (E-MRS) / Symposium L - New developments in the modeling and analysis of radiation damage in materials II, 31.05.-04.06.2021, ONLINE, ONLINE

Permalink: https://www.hzdr.de/publications/Publ-32108
Publ.-Id: 32108


Effect of power ultrasound on wettability and collector-less floatability of chalcopyrite, pyrite and quartz

Ahmad, H.; Hamed, G.; Safak, G. Ö.; Tomasz, N.; Agnieszka, S.

Numerous studies have addressed the role of ultrasonication on floatability of minerals macroscopically. However, the impact of acoustic waves on the mineral hydrophobicity and its physicochemical aspects were entirely overlooked in the literature. This paper mainly investigates the impact of ultrasonic power and its time on the wettability and floatability of chalcopyrite, pyrite and quartz. For this purpose, contact angle and collectorless microflotation tests were implemented on the ultrasonic-pretreated and non-treated chalcopyrite, pyrite and quartz minerals. The ultrasonic process was carried out by a probe-type ultrasound (Sonopuls, 20 kHz and 60 W) at various ultrasonication time (0.5–30 min) and power (0–180 W) while the dissolved oxygen (DO), liquid temperature, conductivity (CD) and pH were continuously monitored. Comparative assessment of wettabilities in the presence of a constant low-powered (60 W) acoustic pre-treatment uncovered that surface of all three minerals became relatively hydrophilic. Meanwhile, increasing sonication intensity enhanced their hydrophilicities to some extent except for quartz at the highest power-level. This was mainly related to generation of hydroxyl radicals, iron-deficient chalcopyrite and elemental sulfur (for chalcopyrite), formation of OH and H radicals together with H2O2 (for pyrite) and creation of SiOH (silanol) groups and hydrogen bond with water dipoles (for quartz). Finally, it was also found that increasing sonication time led to enhancement of liquid temperature and conductivity but diminished pH and degree of dissolved oxygen, which indirectly influenced the mineral wettabilities and floatabilities. Although quartz and pyrite ultrasound-treated micro-flotation recoveries were lower than that of conventional ones, an optimum power-level of 60–90 W was identified for maximizing chalcopyrite recovery.

Keywords: froth flotation; power ultrasound; ultrasonic treatment; chalcopyrite-pyrite-quartz flotation system; hydrophobicity

Permalink: https://www.hzdr.de/publications/Publ-32107
Publ.-Id: 32107


Transformation of tin spheres into hollow cubes by He+ irradiation

Klingner, N.; Heinig, K.-H.; Tucholski, D.; Möller, W.; Hübner, R.; Hlawacek, G.; Facsko, S.

Broad ion irradiation of nanoobjects can considerably change their shape. Examples are ion-beam hammering [1], ion-induced shaping of buried particles [2], and ion-induced viscous flow of nanopillars [3]. Such shape changes are mainly driven by the kinetics of defects generated by binary collisions of ions and recoils. Here we report a new kind of ion-induced structure evolution.
Sub-micrometer Sn spheres were irradiated with 30 keV He+ ions in a Helium Ion Microscope (HIM). Above a He+ fluence of ~ 10E17 /cm², Sn extrusions appear on the surface of the spheres and were imaged with the HIM. Initially, small, pyramid-like facetted extrusions form at the equator of the tin spheres (north pole pointing to the ion source). Later, each sphere becomes completely covered with tin and appears like a facetted single crystal cube. No Sn extrusions were observed for tin spheres with diameters smaller than ~100 nm. Transmission Electron Microscopy and Auger electron spectroscopy studies show that the tin spheres are covered with a few nm thick SnOx skin and that the extrusions are single crystals.

A model was developed which assumes that the He+ ions generate Frenkel pairs in the body-centered tetragonal lattice of tin. The point defects are confined to the tin sphere by the SnO skin, and there is no preferred nucleation or annihilation of the point defects at the Sn-SnO interface. The recombination of interstitials with vacancies is partly inhibited by occupation with He atoms. This results in an increasing pressure of the “interstitial gas”. Simultaneously, He+ ion erosion creates openings in the SnO skin. The sputter coefficient increases with the angle of incidence, so that openings in the SnO skin form in the equator regions first. Once the tin interstitials find an opening in the SnO skin, they can escape from the interior of the Sn sphere and form an epitaxial regular Sn lattice on the outside. Due to the high Sn-SnO bond strength, the extruded tin wets the outer SnO surface.

Computer simulations were performed based on this model. The Frenkel pair generation and the SnO skin sputtering are simulated with dynamical programs based on the Binary Collision Approximation TRI3DYN [4]. Reaction-diffusion dynamics as well as nucleation and extended defect growth were simulated with a 3D kinetic lattice Monte Carlo program [5] using an RGL-potential for tin. The formation of cavities and their filling with He reproduces the experimentally observed tendency for hollow cube formation.

[1] Snoeks et al., Nucl. Instr. Meth B 178 (2001) 62
[2] Schmidt et al., Nucl. Instr. Meth. B 267 (2009) 1345
[3] Xu et al., Semicond. Sci. Technol. 35 (2020) 15021
[4] Möller, Nucl. Instr. Meth. B 322 (2014) 23
[5] Strobel et al., Phys. Rev. B 64 (2001) 245422

Related publications

  • Lecture (Conference) (Online presentation)
    European Materials Research Society 2021 Spring Meeting, 31.05.-04.06.2021, ONLINE, ONLINE
  • Invited lecture (Conferences) (Online presentation)
    FIB SIG User Group Meeting, 24.-25.09.2021, St Lucia Qld, Australia

Permalink: https://www.hzdr.de/publications/Publ-32106
Publ.-Id: 32106


Magnetic structure of the quantum magnet SrCuTe2O6

Chillal, S.; Isman, A. T. M. N.; Luetkens, H.; Canévet, E.; Scurschii, I.; Khalyavin, D.; Lake, B.

SrCuTe2O6 consists of a three-dimensional arrangement of spin-1/2 Cu2+ ions. The first-, second-, and third-neighbor interactions, respectively, couple Cu2+ moments into a network of isolated triangles, a highly frustrated hyperkagome lattice consisting of corner-sharing triangles and antiferromagnetic chains. Of these, the chain interaction dominates in SrCuTe2O62O6 using muon relaxation spectroscopy and neutron diffraction and present the low-temperature magnetic structure as well as the directional-dependent magnetic phase diagram as a function of field.

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Permalink: https://www.hzdr.de/publications/Publ-32105
Publ.-Id: 32105


Momentum distribution function and short-range correlations of the warm dense electron gas -- ab initio quantum Monte Carlo results

Hunger, K.; Schoof, T.; Dornheim, T.; Bonitz, M.; Filinov, A.

In a classical plasma the momentum distribution, n(k), decays exponentially, for large k, and the same is observed for an ideal Fermi gas. However, when quantum and correlation effects are relevant simultaneously, an algebraic decay, n∞(k)∼k−8 has been predicted. This is of relevance for cross sections and threshold processes in dense plasmas that depend on the number of energetic particles. Here we present the first \textit{ab initio} results for the momentum distribution of the nonideal uniform electron gas at warm dense matter conditions. Our results are based on first principle fermionic path integral Monte Carlo (CPIMC) simulations and clearly confirm the k−8 asymptotic. This asymptotic behavior is directly linked to short-range correlations which are analyzed via the on-top pair distribution function (on-top PDF), i.e. the PDF of electrons with opposite spin. We present extensive results for the density and temperature dependence of the on-top PDF and for the momentum distribution in the entire momentum range.

Permalink: https://www.hzdr.de/publications/Publ-32103
Publ.-Id: 32103


Preclinical evaluation of [18F]FACH in healthy mice and piglets: An 18F-labeled ligand for imaging of monocarboxylate transporters with PET

Gündel, D.; Sadeghzadeh, M.; Deuther-Conrad, W.; Wenzel, B.; Cumming, P.; Toussaint, M.; Ludwig, F.-A.; Moldovan, R.-P.; Kranz, M.; Teodoro, R.; Sattler, B.; Sabri, O.; Brust, P.

: The expression of monocarboxylate transporters (MCTs) is linked to pathophysiological changes in diseases including cancer, such that MCTs could potentially serve as diagnostic markers or therapeutic targets. We recently developed [18F]FACH as a radiotracer for non-invasive molecular imaging of MCTs by positron emission tomography (PET). The aim of this study was to evaluate further the specificity, metabolic stability, and pharmacokinetics of [18F]FACH in healthy mice and piglets. We measured the [18F]FACH plasma protein binding fractions in mice and piglets and the specific binding in cryosections of murine kidney and lung. The biodistribution of [18F]FACH was evaluated by tissue sampling ex vivo and by dynamic PET/MRI in vivo, with and without pre-treatment by the MCT inhibitor α-CCA-Na or the reference compound, FACH-Na. Addition-ally, we performed compartmental modelling of the PET signal in kidney cortex and liver. Satu-ration binding studies in kidney cortex cryosections indicated a KD of 118±12 nM and Bmax of 6.0 pmol/mg wet weight. The specificity of [18F]FACH uptake in the kidney cortex was confirmed in vivo by reductions in AUC0-60min after pre-treatment with α-CCA-Na in mice (-47%) and in piglets (-66%). [18F]FACH was metabolically stable in mouse, but polar radio-metabolites were present in plasma and tissues of piglets. The [18F]FACH binding potential (BPND) in the kidney cortex was approximately 1.3 in mice. [18F]FACH has suitable properties for the detection of the MCTs in kidney, and thus has potential as a molecular imaging tool for MCT-related pathologies, which should next be assessed in relevant disease models.

Keywords: monocarboxylate transporters (MCTs); [18F]FACH; PET imaging; metabolism; kidney; cancer

  • Open Access Logo International Journal of Molecular Sciences 22(2021)4, 1645
    Online First (2021) DOI: 10.3390/ijms22041645
    ISSN: 1422-0067

Permalink: https://www.hzdr.de/publications/Publ-32102
Publ.-Id: 32102


Small scale short circuits due to metal-droplet transfer in liquid metal batteries

Benard, S.; Landgraf, S.; Weber, N.; Weier, T.

Liquid metal batteries (LMBs) have been discussed as stationary energy storage for integrating highly volatile renewable energy sources into the electric grid. The cheap and abundant electrode materials, extreme current densities and potentially very long life time make LMBs excellent candidates for storage applications. As a typical cell, Li-Bi LMBs consist of a molten Bi-electrode on the bottom, an ion-conducting liquid electrolyte in the middle and a molten Li-electrode on the top – as illustrated schematically in Fig. 1. In order to avoid contact of the anode with the cell housing, the molten Li is typically contained in a solid Ni-Fe foam. During discharge, the anode metal Li is oxidized, and the ion crosses the electrolyte layer before alloying with the molten Bi. At charge, this process is reversed and Li de-alloyed and transferred back into the metal-foam anode.
When cycling such batteries for several days, sometimes short voltage drop-offs can be observed. As illustrated in Fig. 1, such quick changes of the cell potential can most probably be explained by a sudden non-faradaic Li-transfer from the anode to the cathode. After operating Li-Bi cells and removing the current collector with the Ni-Fe-foam, sometimes solid spots, formed of an intermetallic phase, can be observed below of the foam – as shown in the inset in Fig. 1. These intermetallic phases can appear only if Bi from the cathode touches the anode, e.g. during a localized short circuit. Considering that the metal foam reacts slightly with the molten salt, it might happen that the wetting behavior between molten Li and foam changes with time. A missing wetting could – finally – lead to the formation of small Li-droplets below of the foam when charging the cell. If such droplets grow too much, they might lead to a local short circuit and may thus explain the phenomena illustrated in Fig. 1. Bases on this motivation, the formation, detachment and transport of such droplets as well as a possible short circuit is studied.

  • Lecture (Conference)
    Electromagnetic processing of materials, 13.-17.06.2021, Riga, Lettland

Permalink: https://www.hzdr.de/publications/Publ-32100
Publ.-Id: 32100


Suppression of Metastatic Melanoma Growth in Lung by Modulated Electro-Hyperthermia Monitored by a Minimally Invasive Heat Stress Testing Approach in Mice

Thomas, M. J.; Major, E.; Benedek, A.; Horvath, I.; Mathe, D.; Bergmann, R.; Szasz, A. M.; Krenacs, T.; Benyo, Z.

Modulated electro-hyperthermia (mEHT) is a novel complementary therapy in oncology which is based on the higher conductivity and permittivity of cancerous tissues due to their enhanced glycolytic activity and ionic content compared to healthy normal tissues. We aimed to evaluate the potential of mEHT, inducing local hyperthermia, in the treatment of pulmonary metastatic melanoma. Our primary objective was the optimization of mEHT for targeted lung treatment as well as to identify the mechanism of its potential anti-tumor effect in the B16F10 mouse melanoma pulmonary metastases model while investigating the potential treatment-related side effects of mEHT on normal lung tissue. Repeated treatment of tumor-bearing lungs with mEHT induced significant anti-tumor effects as demonstrated by the lower number of tumor nodules and the downregulation of Ki67 expression in treated tumor cells. mEHT treatment provoked significant DNA double-strand breaks indicated by the increased expression of phosphorylated H2AX protein in treated tumors, although treatment-induced elevation of cleaved/activated caspase-3 expression was insignificant, suggesting the minimal role of apoptosis in this process. The mEHT-related significant increase in p21waf1 positive tumor cells suggested that p21waf1-mediated cell cycle arrest plays an important role in the anti-tumor effect of mEHT on melanoma metastases. Significantly increased CD3+, CD8+ T-lymphocytes, and F4/80+CD11b+ macrophage density in the whole lung and tumor of treated animals emphasizes the mobilizing capability of mEHT on immune cells. In conclusion, mEHT can reduce the growth potential of melanoma, thus offering itself as a complementary therapeutic option to chemo- and/or radiotherapy.

Keywords: B16F10 melanoma; DNA double-strand breaks; cell cycle arrest; immune cell mobilization; modulated electro-hyperthermia; pulmonary metastases

Permalink: https://www.hzdr.de/publications/Publ-32099
Publ.-Id: 32099


Solar and anthropogenic influences on climate: Regression analysis and tentative predictions

Stefani, F.

The two main drivers of climate change on sub-Milankovitch time scales are re-assessed by means of a double regression analysis. Evaluating linear combinations of the logarithm of carbon dioxide concentration and the geomagnetic aa-index as a proxy for solar activity, we reproduce the sea surface temperature (HadSST) since the middle of the 19th century with an adjusted R² value of around 87 per cent for a climate sensitivity (of TCR type) in the range of 0.6 K until 1.6 K per doubling of CO₂ . The solution of the regression is quite sensitive: when including data from the last decade, the simultaneous occurrence of a strong El Niño and low aa-values lead to a preponderance of solutions with relatively high climate sensitivities around 1.6 K. If those later data are excluded, the regression delivers a significantly higher weight of the aa-index and correspondingly a lower climate sensitivity going down to 0.6 K. The plausibility of such low values is discussed in view of recent experimental and satellite-borne measurements. We argue that a further decade of data collection will be needed to allow for a reliable distinction between low and high sensitivity values. Based on recent ideas about a quasi-deterministic planetary synchronization of the solar dynamo, we make a first attempt to predict the aa-index and the resulting temperature anomaly for various typical CO₂ scenarios. Even for the highest climate sensitivities, and an unabated linear CO₂ increase, we predict only a mild additional temperature rise of around 1 K until the end of the century, while for the lower values an imminent temperature drop in the near future, followed by a rather flat temperature curve, is prognosticated.

Keywords: Climate change; Solar cycle; Forecast

Permalink: https://www.hzdr.de/publications/Publ-32098
Publ.-Id: 32098


Metal ion size profoundly affects H3glyox chelate chemistry

Choudhary, N.; Barett, K.; Kubeil, M.; Radchenko, V.; Engle, J.; Stephan, H.; de Guadalupe Jaraquemada-Pelaez, M.; Orvig, C.

The bisoxine hexadentate chelating ligand H3glyox was investigated for its affinity for Mn2+, Cu2+ and Lu3+ ions; all three metal ions are medicinally relevant with applications in nuclear medicine and medicinal inorganic chemistry. The aqueous coordination chemistry and thermodynamic stability of all three metal complexes was thoroughly investigated by detailed DFT structure calculations and stability constant determination, by employing UV in-batch spectrophotometric titrations, giving pM values – pCu (25.2) > pLu (18.1) > pMn (12.0). DFT calculated structures revealed different geometries and coordination preferences of the three metal ions; notable was an inner sphere water molecule in the Mn2+ complex. H3glyox labels [52Mn]Mn2+, [64Cu]Cu2+ and [177Lu]Lu3+ at ambient conditions with apparent molar activities of 40 MBq/mol, 500 MBq/mol and 25 GBq/mol, respectively. Collectively, these initial investigations provide significant insight into the effects of metal ion size and charge on the chelation with the hexadentate H3glyox and the potential use of the Mn2+-H3glyox complex in 52/55Mn-based bimodal imaging.

Permalink: https://www.hzdr.de/publications/Publ-32097
Publ.-Id: 32097


Radial pressure forces in Euler-Euler simulations of turbulent bubbly pipe flows

Rzehak, R.; Liao, Y.; Meller, R.; Schlegel, F.; Lehnigk, R.; Lucas, D.

Two-equation turbulence models based on the Boussinesq eddy viscosity hypothesis that have been used in the vast majority of previous simulation studies on bubbly pipe flows contain a term which renders the radial pressure distribution non-constant. In single phase simulations this effect is invariably absorbed in the definition of a modified pressure, from which the real pressure may be recovered if necessary. For bubbly multiphase flows however, this is not possible since the bubbles experience a force which depends, of course, on the real pressure rather than the modified one. As it turns out, most software codes by default rely on the approximation of neglecting the difference between modified and real pressure for bubbly flows. The purpose of the present study is to assess the influence of this approximation on the final simulations results. Fortunately it turns out that at least for the conditions considered in this study, the error is small.

Keywords: turbulent dispersed gas liquid multiphase flow; Euler-Euler two fluid model; closure relations; CFD

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Permalink: https://www.hzdr.de/publications/Publ-32095
Publ.-Id: 32095


Synthesis and radiofluorination of [18F]F-BAY-8002: A novel potential radiotracer for PET imaging of monocarboxylate transporter 1

Sadeghzadeh, M.; Wenzel, B.; Ludwig, F.-A.; Kopka, K.; Moldovan, R.-P.; Brust, P.

Objectives: The monocarboxylate transporters 1 and 4 (MCT1/4) are integral plasma membrane proteins that bi-directionally transport lactate as well as small monocarboxylated molecules. They are highly expressed in several tumors. BAY-8002 belongs to a class of compounds that have been identified as novel and specific MCT1 inhibitors based on functional high-throughput screening assays using a panel of cell lines highly sensitive towards MCT1 inhibition [1]. IC50 values of 1 to 12 nM and ca. 500–fold selectivity towards MCT4 have already been reported for BAY-8002 [1]. Here we designed an 18F-labeled analog of BAY-8002 ([18F]F-BAY-8002) aiming to image mainly MCT1 upregulation considering the fact that the absence of MCT4 expression in many types of cancer may not be necessarily sufficient as a single marker to predict treatment response [2].
Methods: BAY-8002 and its novel fluorinated analog (F-BAY-8002) were synthesized based on reported procedures [1]. As BAY-8002 already contains a chloro substituent which could serve as leaving group, the compound was considered as precursor for radiofluorination via a halogen-fluorine exchange approach (Figure 1A). [18F]F-BAY-8002 was radiolabeled via a one-step aromatic nucleophilic substitution reaction (SNAr) using 2-5 mg of precursor in the presence of the [18F]KF/K222/K2CO3 complex in dimethyl sulfoxide (DMSO) at 150 °C within 5 min (Figure 1B).

Figure 1. (A) Synthesis of BAY-8002 and its novel fluorinated analog; (B) Radiosynthesis of [18F]F-BAY-8002.
Separation of [18F]F-BAY-8002 from the chlorinated precursor was performed by semi-preparative HPLC. The tracer was finally purified via solid-phase extraction (Sep-Pak® C18 light cartridge) and formulated in 10% EtOH/saline solution to be ready for biological evaluations.
Results: Despite using identical conditions [1], the novel fluorinated analog F-BAY-8002 was obtained in only 4% overall yield due to formation of by-products which have not been observed during the synthesis of BAY-8002 (35% overall yield). Due to the lack of commercially available radioligands, the MCT1 affinity (Ki) of F-BAY-8002 could not yet be determined and we therefore intend to measure the KD value of our new radiotracer by in-house established methods in near future. The novel radiotracer [18F]F-BAY-8002 was synthesized in 30 ± 9% radiochemical yields (n = 4, non-isolated, estimated by radio-HPLC) within 5 min reaction time. After purification and formulation, the final product was obtained with a radiochemical purity of > 99% (n = 1). Further radiochemical characterization of the radiotracer and the transfer of the radiosynthesis to an automated module are in progress.
Conclusions: A novel 18F-labeled radioligand for potential specific MCT1-targeted imaging was developed via a straightforward fast approach in good radiochemical yields and high radiochemical purity. Notably, the labeling was successful even without protection of the carboxylic acid group resulting in a beneficial one-step instead of a two-step radiosynthesis procedure. In vitro and in vivo biological evaluation of the newly synthesized MCT1 radioligand are currently ongoing.
References: [1] Quanz, M. et al. Mol Cancer Ther. 2018 17:2285-2296; [2] Le Floch, R. et al. Proc Natl Acad Sci USA. 2011 108:16663-8.

Keywords: Radiofluorination; Monocarboxylate transporter 1; BAY-8002; PET imaging; Cancer

  • Contribution to proceedings
    virtual SRS meeting, 17.-19.05.2021, online, online
    Nuclear Medicine and Biology 96-97, Suppl., Nuclear Medicine and Biology, S74-S75
    DOI: 10.1016/S0969-8051(21)00386-3

Permalink: https://www.hzdr.de/publications/Publ-32094
Publ.-Id: 32094


Magnetische Kühlung

Gottschall, T.

  • Lecture (others)
    Seniorenakademie der TU Dresden, 15.09.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32093
Publ.-Id: 32093


Advanced characterization of multicaloric materials in pulsed magnetic fields

Gottschall, T.

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  • Invited lecture (Conferences) (Online presentation)
    JEMS 2020, 07.12.2020, Lissabon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-32092
Publ.-Id: 32092


Dynamics of Rising Bubbles in a Quiescent Slag Bath with Varying Thermo-Physical Properties

Reuter, M. A.; Obiso, D.; Schwittala, D. H.; Korobeinikov, I.; Meyer, B.; Richter, A.

The motion of bubbles in a liquid slag bath with temperature gradients is investigated by means of 3D fluid dynamic computations. The goal of the work is to describe the dynamics of the rising bubbles, taking into account the temperature dependency of the thermo-physical properties of the slag. Attention is paid to the modeling approach used for the slag properties and how this affects the simulation of the bubble motion. In particular, the usage of constant values is compared to the usage of temperature-dependent data, taken from models available in the literature and from in-house experimental measurements. Although the present study focuses on temperature gradients, the consideration of varying thermo-physical properties is greatly relevant for the fluid dynamic modeling of reactive slag baths, since the same effect is given by heterogeneous species and solid fraction distributions. CFD is applied to evaluate the bubble dynamics in terms of the rising path, terminal bubble shape, and velocity, the gas–liquid interface area, and the appearance of break-up phenomena. It is shown that the presence of a thermal gradient strongly acts on the gas–liquid interaction when the temperature-dependent properties are considered. Furthermore, the use of literature models and experimental data produces different results, demonstrating the importance of correctly modeling the slag’s thermo-physical properties.

Keywords: rising bubbles; liquid slag

Permalink: https://www.hzdr.de/publications/Publ-32091
Publ.-Id: 32091


Local short-circuits in liquid metal batteries - influence of the contact angle on the droplet movement in VOF-simulations

Benard, S.; Landgraf, S.; Weber, N.; Weier, T.

The presentation will give an overview about Li-droplet formation, as well as their detachment and transport, which finally might lead to a localised short-circuit in liquid metal batteries.

  • Lecture (Conference)
    16th OpenFOAM Workshop 2021, 08.-11.06.2021, Dublin, Ireland

Permalink: https://www.hzdr.de/publications/Publ-32090
Publ.-Id: 32090


Ultrathin Co films with Pt and Au covers - magnetic and structural properties driven by Ga+ ion irradiation

Mazalski, P.; Ohnoutek, L.; Sveklo, I.; Beran, L.; Kurant, Z.; Powroźnik, W.; Wawro, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Faßbender, J.; Hamrle, J.; Antoš, R.; Kletecka, V.; Veis, M.; Maziewski, A.

The X/Co 3nm/Y (where X, Y=Au, Pt) trilayers with as deposited in-plane magnetization alignment were irradiated with 30 keV Ga+ ions in the wide range of ion fluence. The samples were investigated by means of complementary techniques: magneto-optical magnetometry and spectroscopy (in the photon energy range from 1.2 eV to 4.5 eV), magnetic force microscopy, positron annihilation spectroscopy, X-ray diffraction and reflectivity. Difference in miscibility of interface atoms is clearly manifested in various intermixing extent at Co/Pt and Co/Au interfaces and consequently in magnetic properties of the irradiated trilayers. Low irradiation fluence (~1014 ions/cm2) leads to ~1nm interfaces broadening without visible surface etching for all samples, which is related with a distinct drop of magnetic anisotropy. However, the high irradiation fluence (~5·1015 ions/cm2) results in enhanced interface broadening and significant surface etching (~5 nm) partially removing also Co atoms. Tensile strains (up to 0.5%) were developed in the cover layers. The tensile strain, layers intermixing and the creation of Co-Pt(Au) alloys with different composition formed by irradiation are correlated with the increase of magnetic anisotropy. Moreover it was observed that substitution of Au instead of Pt (as a cap or buffer layer) results in substantial increase of perpendicular magnetic anisotropy. Maximal increase of magnetooptical parameters was observed for Pt/Co/Pt layer. Irradiation induced changes of concentration profiles are revealed using magnetooptical spectra, X-ray reflectivity spectra and simulations with use of binary collision approximation.

Keywords: perpendicular magnetic anisotropy; ion irradiation; positron annihilation spectroscopy; magneto-optical Kerr spectroscopy; molecular beam epitaxy

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Permalink: https://www.hzdr.de/publications/Publ-32089
Publ.-Id: 32089


Thermoelectric Performance of the Half-Heusler Phases RNiSb (R = Sc, Dy, Er, Tm, Lu): High Mobility Ratio between Majority and Minority Charge Carriers

Ciesielski, K.; Synoradzki, K.; Veremchuk, I.; Skokowski, P.; Szymanski, D.; Grin, Y.; Kaczorowski, D.

Deeper understanding of electrical and thermal transport is critical for further development of thermoelectric materials. Here we describe the thermoelectric performance of a group of rare-earth-bearing half-Heusler phases determined in a wide temperature range. Polycrystalline samples of ScNiSb, DyNiSb, ErNiSb, TmNiSb, and LuNiSb are synthesized by arc melting and densified by spark plasma sintering. They are characterized by powder x-ray diffraction and scanning electron microscopy. The physical properties are studied by means of heat-capacity and Hall-effect measurements performed in the temperature range from 2 to 300 K, as well as electrical-resistivity, Seebeck-coefficient, and thermal-conductivity measurements performed in the temperature range from 2 to 950 K. All the materials except TmNiSb are found to be narrow-gap intrinsic p-type semiconductors with rather light charge carriers. In TmNiSb, the presence of heavy holes with large weighted mobility is evidenced by the highest power factor among the series (17 mu W K-²cm(-¹) at 700 K). The experimental electronic relaxation time calculated with the parabolic band formalism is found to range from 0.8 x 10(-¹⁴) to 2.8 x 10(-¹⁴) s. In all the materials studied, the thermal conductivity is between 3 and 6 W m(-¹) K-¹ near room temperature (i.e., smaller than in other pristine d-electron half-Heusler phases reported in the literature). The experimental observation of the reduced thermal conductivity appears fully consistent with the estimated low sound velocity as well as strong point-defect scattering revealed by Debye-Callaway modeling. Furthermore, analysis of the bipolar contribution to the measured thermal conductivity yields abnormally large differences between the mobilities of n-type and p-type carriers. The latter feature makes the compounds examined excellent candidates for further optimization of their thermoelectric performance via electron doping.

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Permalink: https://www.hzdr.de/publications/Publ-32088
Publ.-Id: 32088


Discovery of high-performance thermoelectric copper chalcogenide using modified diffusion-couple high-throughput synthesis and automated histogram analysis technique

Deng, T.; Xing, T.; Brod, M. K.; Sheng, Y.; Qiu, P.; Veremchuk, I.; Song, Q.; Wei, T.-R.; Yang, J.; Snyder, G. J.; Grin, Y.; Chen, L.; Shi, X.

Discovery of novel high-performance materials with earth-abundant and environmentally friendly elements is a key task for civil applications based on advanced thermoelectric technology. Advancements in this area are greatly limited by the traditional trial-and-error method, which is both time-consuming and expensive. The materials genome initiative can provide a powerful strategy to screen for potential novel materials using high-throughput calculations, materials characterization, and synthesis. In this study, we developed a modified diffusion-couple high-throughput synthesis method and an automated histogram analysis technique to quickly screen high-performance copper chalcogenide thermoelectric materials, which has been well demonstrated in the ternary Cu-Sn-S compounds. A new copper chalcogenide with the composition of Cu₇Sn₃S₁₀ was discovered. Studies on crystal structure, band gap, and electrical and thermal transport properties were performed to show that it is a promising thermoelectric material with ultralow lattice thermal conductivity, moderate band gap, and decent electrical conductivity. Via Cl doping, the thermoelectric dimensionless figure of merit zT reaches 0.8 at 750 K, being among the highest values reported in Cu-Sn-S ternary materials. The modified diffusion-couple high-throughput synthesis method and automated histogram analysis technique developed in this study also shed light on the development of other advanced thermoelectric and functional materials.

Keywords: ultralow thermal conductivity; ternary; scattering; sulfides; Cu₂SnS₃; model

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Permalink: https://www.hzdr.de/publications/Publ-32087
Publ.-Id: 32087


Robust Fermi-Surface Morphology of CeRhIn5 across the Putative Field-Induced Quantum Critical Point

Mishra, S.; Hornung, J.; Raba, M.; Klotz, J.; Förster, T.; Harima, H.; Aoki, D.; Wosnitza, J.; McCollam, A.; Sheikin, I.

We report a comprehensive de Haas–van Alphen (dHvA) study of the heavy-fermion material CeRhIn5 in magnetic fields up to 70 T. Several dHvA frequencies gradually emerge at high fields as a result of magnetic breakdown. Among them is the thermodynamically important β1 branch, which has not been observed so far. Comparison of our angle-dependent dHvA spectra with those of the non-4f compound LaRhIn5 and with band-structure calculations evidences that the Ce 4f electrons in CeRhIn5 remain localized over the whole field range. This rules out any significant Fermi-surface reconstruction, either at the suggested nematic phase transition at B* ≈ 30 T or at the putative quantum critical point at Bc ≃ 50 T. Our results rather demonstrate the robustness of the Fermi surface and the localized nature of the 4f electrons inside and outside of the antiferromagnetic phase.

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Permalink: https://www.hzdr.de/publications/Publ-32086
Publ.-Id: 32086


Can microorganisms significantly influence cast iron corrosion in a DGR?

Matschiavelli, N.; Sushko, V.; Dressler, M.; Neubert, T.; Kühn, L.; Schierz, A.; Cherkouk, A.

For the safe storage of high-level radioactive waste (HLW) in deep geological repositories (DGR), several metals could potentially act as canister material and are under investigation with respect to their properties under disposal-relevant conditions. An essential requirement for the selected metal(s) is the long-term stability which is mainly realized by the resistance to corrosion. The process of corrosion depends on the overall environment in the surrounding of the metal canister and which will change over time. Here, parameters like redox potential, pH, the presence of (pore-) water, the salinity and also the presence of metabolically active microorganisms are of relevance, among others. In order to analyze the influence of different pore waters and the natural microbial community of a Bavarian bentonite, which acts as geotechnical barrier and will be in direct contact to the canister, microcosm experiments were set up. These slurry experiments contained B25 bentonite, synthetic Opalinus Clay pore water or saline cap rock solution as well as copper- or cast iron plates in various combinations. During an incubation time of 400 days under anaerobic conditions at 37 °C, several bio-geochemical parameters (e.g. pH, redox potential and the concentration of minerals, sulfate, iron(II/III) and organic acids) were analyzed as well as the corrosion process and a potential microbial influence. The obtained results provide insights into the complex interplay between bentonite, pore water, metals and microorganisms. Different precipitates like carbonates, iron oxides and sulfides were identified on the cast iron surface, potentially accelerating or slowing down the corrosion process and, thus, affecting the long-term stability of the metal canister in a DGR.

  • Lecture (Conference) (Online presentation)
    EGU 2021 General Assembly, 19.-30.04.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32085
Publ.-Id: 32085


Magnetoelastic study on the frustrated quasi-one-dimensional spin-1/2 magnet LiCuVO4

Miyata, A.; Hikihara, T.; Furukawa, S.; Kremer, R. K.; Zherlitsyn, S.; Wosnitza, J.

We investigated the magnetoelastic properties of the quasi-one-dimensional spin-1/2 frustrated magnet LiCuVO4. Longitudinal-magnetostriction experiments were performed at 1.5 K in high magnetic fields of up to 60 T applied along the b axis, i.e., the spin-chain direction. The magnetostriction data qualitatively resemble the magnetization results, and saturate at Hsat ≈ 54 T, with a relative change in sample length of ΔL/L ≈ 1.8 × 10−4. Remarkably, both the magnetostriction and the magnetization evolve gradually between Hc3 ≈ 48 T and Hsat, indicating that the two quantities consistently detect the spin-nematic phase just below the saturation. Numerical analyses for a weakly coupled spin-chain model reveal that the observed magnetostriction can overall be understood within an exchange-striction mechanism. Small deviations found may indicate nontrivial changes in local correlations associated with the field-induced phase transitions.

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Permalink: https://www.hzdr.de/publications/Publ-32083
Publ.-Id: 32083


Advanced mineral exploration in the glaciated terrain using topsoil geochemistry and the compositional statistical data analysis

Sarala, P.; Pospiech, S.; Middleton, M.; Taivalkoski, A.; Hulkki, H.

Mineral exploration in northern, vulnerable nature areas demands on the development of new, environmentally friendly sampling and analyses techniques. Those areas are typically covered by the transported cover of which the glacigenic sediments such as a till are the most dominant as a result of several glaciation stages. To avoid conventional basal till and bedrock sampling using heavy machines, the use of different surface geochemical sampling media and techniques have increased recently. Particularly, the development of selective and weak leach techniques for the topsoil (Ah and B horizons) geochemistry has been intensive, and the use of those techniques has led to the observation of new mineralization.
In this research, carried out under the project New Exploration Technologies (NEXT), funded by the European Union’s Horizon 2020 research and innovation programme, we used stratified random sampling strategy for creating a sampling grid and developed novel compositional statistical data analysis for the interpretation of geochemical data obtained by the multi-source surface geochemical techniques. The test area located in northern Finland where there is an active exploration campaign going on for Au-U-Co mineralizations in the Rajapalot area, Ylitornio by the Mawson Oy. Glacial morphology in the study area is dominated by the ribbed moraine ridges with peatlands in between. The thickness of till cover varied from some metres to 15 m. A sampling network for both the Ah and B horizon samples comprised 98 proper and 10 field duplicate sampling stations from the mineral soil dominated by the Podsol-type soil horizon. The chemical analyses methods used were Ultratrace 1:1:1 Aqua Regia leach and 0.1 M sodium pyrophosphate leach for the Ah horizon samples, and Ionic leach and Super Trace Aqua Regia leach methods for the B horizon samples. The laboratory analyses were supported by the portable X-Ray Fluorescence (pXRF) analyses done directly in the field. The statistical analysis methods of the results were based on conventional supervised and unsupervised classification techniques using as explanatory variables: a) log-ratio transformations of the geochemical compositions, b) enrichment factors between sampled media, and c) the summaries of the two preceding systems of variables provided by the parallel principal component analysis.
The preliminary results of the topsoil geochemistry show a significant response to many elements to known geochemical features and elevated contents in the base-of-till and underlying bedrock geochemical data. Anomaly patterns are also reflecting the lithological variations of the rock units in the bedrock. Based on the results, it is obvious that a) there is good correlation between the surface geochemistry and underlying bedrock, b) stratified randomization in the planning phase and statistical methods in data interpretation stage increases the quality of the data and the reliability of geochemical exploration, and c) topsoil sampling with selective analysis methods is effective and environmentally friendly geochemical exploration technique in the glaciated terrains.

Keywords: soil; mineral exploration

Permalink: https://www.hzdr.de/publications/Publ-32082
Publ.-Id: 32082


Snow as proxy for mineral exploration – a case study from Northern Finland

Pospiech, S.; Taivalkoski, A.; Lahaye, Y.; Sarala, P.; Kinnunen, J.; Middleton, M.

Modern mineral exploration techniques for Europe are required to be sustainable, environmental friendly and social acceptable. Especially for the geochemical exploration of the ecologically sensitive areas of northern Europe this poses a challenge, because any heavy machinery or invasive methods might cause long-lasting damage to the natural systems. One way of reducing the impact of mineral exploration on the environment during early stages of the exploration is to use surface media, such as upper soil horizons, water, plants and snow. Of these options, snow has several advantages: Sampling and analysing snow is fast and low in costs, it has no impact on the environment, and it is (in winter time) ubiquitous, i.e. available independent of land cover and environment.
In the “New Exploration Technologies (NEXT)” project, funded by the European Union’s Horizon 2020 research and innovation programme, 171 snow samples and 13 field duplicate snow samples for quality control, were collected in March-April 2019 to strengthen the idea of using snow as a sampling material for mineral exploration. The Rajapalot Au-Co prospect in northern Finland, 60 km west from Rovaniemi and operated by Mawson Oy, was selected as a test site. Stratified random sampling was used to create the uneven sampling net over the test area. The samples were analysed at GTK using a Nu AttoM single collector inductively coupled plasma mass spectrometry (SC-ICPMS) which returned analytical results for 52 elements at the ppt level. Due to strict quality control, only Ba, Ca, Cr, Cs, Ga, Li, Mg, Rb, Sb, Sr, Tk, V and Zn passed and were used in the final data analysis.
The preliminary results based on PCA show a strong dependency of snow composition on the soil type. That is, there is a difference if the snow sample was taken above mineral soil or organic soil. Thus, the soil type should be included in the models or the data analysis should be looked separately for different soil types. The linear model predictions were used to test if the snow geochemistry can predict the bedrock geochemistry. For Al, Ca, Li, Sr and Na the prediction works well. Instead of using snow directly for detecting the mineralization for pinpointing drill targets for exploration purposes, snow geochemistry could be used as a lithogeochemical mapping tool to delineate the areas where to continue exploration with more sensitive methods.

Keywords: snow; mineral exploration; compositional data; environmental friendly; sustainable; NEXT

  • Lecture (Conference) (Online presentation)
    EGU General Assembly 2021, 19.-30.04.2021, online, Austria

Permalink: https://www.hzdr.de/publications/Publ-32081
Publ.-Id: 32081


Tuning of ferromagnetic behavior of GaN films by N ion implantation: an experimental and first principle-based study

Singh, P.; Ghosh, S.; Mishra, V.; Barman, S.; Barman, S. R.; Singh, A.; Kumar, S.; Li, Z.; Kentsch, U.; Srivastava, P.

Magnetic properties of N-ion implanted GaN films (150 nm) have been reported. It is found that GaN films grown by the MOCVD technique show strong room temperature ferromagnetic behavior, which can be tuned by implanting N-ions at different fluences (1×10¹⁵ to 5×10¹⁶ ions- cm⁻²). Presence of implanted N at interstitial sites of the GaN host matrix is indicated from the strain observed in GaN by analysis of XRD data. PL spectra show presence of different types of defects in the as deposited film and engineering of defects after N-ion implantation. XPS spectra of Ga 3d-core level and valence band reveal the bonding of implanted N with the host Ga and/or N. The origin of ferromagnetic behavior is ascribed to unpaired electrons created at N sites due to Ga vacancies. First principle-based calculations also confirm ferromagnetism due to Ga vacancies and the reduction of magnetic behavior in Ga deficient GaN with N-ion implantation at interstitial site. The systematic reduction in the saturation magnetic moment value after N-ion implantation is explained on the basis of pairing of the unpaired electrons due to the bond formation of interstitial N with Ga and N present in the host matrix.

Keywords: ion implantation; defects; ferromagnetism; nitrogen interstitials; tuning

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Permalink: https://www.hzdr.de/publications/Publ-32080
Publ.-Id: 32080


Magnetic Refrigeration: From material to application

Gottschall, T.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences)
    31. Edgar Lüscher Seminar, 09.02.2020, Klosters, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-32079
Publ.-Id: 32079


Recent progress and future projects at HLD and LNCMI - Toulouse

Miyata, A.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    The 16th Japanese High Magnetic Field Forum, 03.12.2020, Tuhoku, Japan

Permalink: https://www.hzdr.de/publications/Publ-32078
Publ.-Id: 32078


Variable relative biological effectiveness (RBE) in proton therapy of gliomas

Eulitz, J.; Raschke, F.; Seidlitz, A.; Hahn, C.; Permatassari, F.; Lutz, B.; Schulz, E.; Karpowitz, C.; Grey, A.; Engellandt, K.; Löck, S.; Troost, E. G. C.; Krause, M.; Lühr, A.

Purpose:

Currently, there is an intense debate on the need to consider variable clinical relative biological effectiveness (RBE) in proton therapy. Here, the variability of the clinical RBE is studied for late radiation-induced brain injuries (RIBI) observed after proton therapy in WHO grade 2-3 glioma patients.

Methods: In total, 42 patients out of a consecutive WHO grade 2-3 glioma patient cohort that received (adjuvant) proton radio(chemo)therapy between 2014 and 2017, were eligible for analysis. RIBI lesions (symptomatic or clinically silent) were diagnosed and delineated on T1-weighted magnetic resonance imaging with contrast agent scans obtained in the first two years of follow-up. Correlation of RIBI location and occurrence with simulated dose (D), proton linear energy transfer (LET, dose-averaged) and variable RBE dose parameters were tested in voxel- and in patient-wise logistic regression analyses, respectively. Additionally, anatomical and clinical parameters were considered and model performance was estimated through cross-validated area-under-the-curve (AUC) values.

Results: In 23 patients, 69 RIBI lesions were diagnosed. RIBI location and occurrence were significantly correlated with D×LET and variable RBE dose in voxel- and patient-wise regression analysis with cross-validated AUC values of 0.90 (95% confidence interval: 0.90-0.90) and 0.83 (0.60-1.00), respectively, when incorporating the periventricular region and tumor histology in the analysis. Models without D×LET and constant RBE revealed AUC values of 0.88 (0.88-0.88) and 0.78 (0.51-1.00), respectively.

Conclusions: Models with variable RBE performed substantially better in predicting occurrence and location of RIBI when compared to fixed RBE models. The obtained clinical evidence for a variable proton RBE suggests its consideration in proton treatment planning of brain tumors.

Keywords: Variable proton RBE; Glioma; Radiation-induced brain injury; Periventricular region; LET

  • Invited lecture (Conferences) (Online presentation)
    59th Annual Conference of the Particle Therapy Co-Operative Group, 04.-07.06.2021, Dresden (Online), Germany

Permalink: https://www.hzdr.de/publications/Publ-32077
Publ.-Id: 32077


Magnetoelastic coupling in frustrated magnets: The cases of LiCuVO4 and MnCr2S4

Miyata, A.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    ARHMF 2020 and KINKEN Materials Science School 2020 for Young Scientists, 02.12.2020, Tohoku, Japan

Permalink: https://www.hzdr.de/publications/Publ-32076
Publ.-Id: 32076


Pressure-tuned magnetic interactions in the triangular-lattice Quantum antiferromagnet Cs2CuCl4

Zvyagin, S.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    ARHMF 2020 and KINKEN Materials Science School 2020 for Young Scientists, 01.-03.12.2020, Tohoku, Japan

Permalink: https://www.hzdr.de/publications/Publ-32075
Publ.-Id: 32075


Contactless generation of cavitation in high temperature liquid metals and its impact on particle dispersion in solidified iron and steel samples

Sarma, M.; Grants, I.; Herrmannsdörfer, T.; Gerbeth, G.

A recently developed method for the contactless magnetic generation of cavitation is demonstrated for high-melting-point metals. The approach is based on the floating-zone technique, which is truly contactless and crucible-free as it uses electromagnetic forces. Using this method, ultra-high-temperature ceramic particles, such as TiN, TiB₂ and TiC, are admixed in liquid iron and 316L steel. The dispersion and particle refinement caused by cavitation treatment during melting and solidification are investigated. Magnetic fields up to 8 T that correspond to pressure oscillation amplitude of 0.83 MPa are used. The signal emitted by the collapsing bubbles is captured and visualized for iron melts. Samples with a higher number of cavitation nuclei exhibit a more stable cavitation response. Improved reinforcement refinement is demonstrated for increasing cavitation intensity – the size of precipitates is evidently reduced due to the cavitation
treatment.

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Permalink: https://www.hzdr.de/publications/Publ-32074
Publ.-Id: 32074


Spin dynamics in low-D spin systems: high-field ESR

Zvyagin, S.

es lag kein aussagefähiges Abstract vor

  • Invited lecture (Conferences) (Online presentation)
    Workshop on Neutrons and Complementary Techniques for Quantum Materials, 18.-21.08.2020, Oak Ridge, USA

Permalink: https://www.hzdr.de/publications/Publ-32073
Publ.-Id: 32073


Shaken and stirred: When Bond meets Suess-de Vries and Gnevyshev-Ohl

Stefani, F.; Stepanov, R.; Weier, T.

We argue that the most prominent temporal features of the solar dynamo, in particular the Hale cycle, the Suess de Vries cycle (associated with variations of the Gnevyshev-Ohl rule), Gleissberg-type cycles, and grand minima can be self-consistently explained by double synchronization with the 11.07-years periodic tidal forcing of the Venus-Earth-Jupiter system and the (mainly) 19.86-years periodic motion of the Sun around the barycenter of the solar system. In our numerical simulation, grand minima, and clusters thereof, emerge as intermittent and non periodic events on millennial time scales, very similar to the series of Bond events which were observed throughout the Holocene and the last glacial period. If confirmed, such an intermittent transition to chaos would prevent any long-term prediction of solar activity, notwithstanding the fact that the shorter-term Hale and Suess-de Vries cycles are clocked by planetary motion.

Keywords: solar cycle

Permalink: https://www.hzdr.de/publications/Publ-32072
Publ.-Id: 32072


Schwabe, Gleissberg, Suess-de Vries: Towards a consistent model of planetary synchronization of solar cycles

Stefani, F.; Giesecke, A.; Seilmayer, M.; Stepanov, R.; Weier, T.

Aiming at a consistent planetary synchronization model of both short-term and long-term solar cycles, we start with an analysis of Schove’s historical data of cycle maxima. Their deviations (residuals) from the average cycle duration of 11.07 years show a high degree of regularity, comprising a dominant 200 year period (Suess-de Vries cycle), and a few periods around 100 years (Gleissberg cycle). Encouraged by their robustness, we support previous forecasts of an upcoming grand minimum in the 21st century. To explain the long-term cycles, we enhance our tidally synchronized solar dynamo model by a modulation of the field storage capacity of the tachocline with the orbital angular momentum of the Sun, which is dominated by the 19.86-year periodicity of the Jupiter–Saturn synodes. This modulation of the 22.14-year Hale cycle leads to a 193-year beat period of dynamo activity which is indeed close to the Suess-de Vries cycle. For stronger dynamo modulation, the model produces additional peaks at typical Gleissberg frequencies, which seem to be explainable by the non-linearities of the basic beat process, leading to a bi-modality of the Schwabe cycle. However, a complementary role of beat periods between the Schwabe cycle and the Jupiter–Uranus/Neptune synodic cycles cannot be completely excluded.

Keywords: solar cycle

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Permalink: https://www.hzdr.de/publications/Publ-32071
Publ.-Id: 32071


Evolution of a strong electrovortex flow in a cylindrical cell

Kolesnichenko, I.; Frick, P.; Eltishchev, V.; Mandrykin, S.; Stefani, F.

The mechanism of poloidal flow suppression in an electrovortex flow (EVF) is verified in a liquid metal experiment and supported by numerical simulations. Beyond a certain threshold of azimuthal forcing, a strong poloidal EVF flow develops only transiently, before the centrifugal forces of the slowly generated swirl compensate the EVF-driving forces. This result shows that EVFs can become of particular importance in large-scale liquid metal batteries, especially during the switch-on regime when the transient poloidal flows can be up to two orders of magnitude stronger than those expected in the saturated regime.

Keywords: electrovortex flow

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-32070
Publ.-Id: 32070


Overview of mico- and millifluidic prototyping and sensing approaches

Schütt, J.; Makarov, D.

Kick-Off Präsentation des HZDRs im Zuge des Projektstarts. Angesprochene Themengebiete umfassen die aktuellen und zukünftigen Arbeitsgebiete der Arbeitsgruppe "Fluid Sensorics".

Keywords: Fluidic Sensorics; SiNW FETs; Nano-capacitors; Planar Hall Effect Sensors

  • Lecture (others) (Online presentation)
    Initial Scientific Meeting, 12.11.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32069
Publ.-Id: 32069


Using Diffuse Scattering to Observe X-Ray-Driven Nonthermal Melting

Hartley, N.; Grenzer, J.; Huang, L.; Inubushi, Y.; Kamimura, N.; Katagiri, K.; Kodama, R.; Kon, A.; Lu, W.; Makita, M.; Matsuoka, T.; Nakajima, S.; Ozaki, N.; Pikuz, T.; Rode, A. V.; Sagae, D.; Schuster, A.; Tono, K.; Voigt, K.; Vorberger, J.; Yabuuchi, T.; McBride, E. E.; Kraus, D.

We present results from the SPring-8 Angstrom Compact free electron LAser facility, where we used a high intensity (∼10^20 W/cm2) x-ray pump x-ray probe scheme to observe changes in the ionic structure of silicon induced by x-ray heating of the electrons. By avoiding Laue spots in the scattering signal from a single crystalline sample, we observe a rapid rise in diffuse scattering and a transition to a disordered, liquidlike state with a structure significantly different from liquid silicon. The disordering occurs within 100 fs of irradiation, a timescale that agrees well with first principles simulations, and is faster than that predicted by purely inertial behavior, suggesting that both the phase change and disordered state reached are dominated by Coulomb forces. This method is capable of observing liquid scattering without masking
signal from the ambient solid, allowing the liquid structure to be measured throughout and beyond the phase change.

Permalink: https://www.hzdr.de/publications/Publ-32068
Publ.-Id: 32068


Design and performance characterisation of the HAPG von Hámos Spectrometer at the High Energy Density Instrument of the European XFEL

Preston, T. R.; Göde, S.; Schwinkendorf, J.-P.; Appel, K.; Brambrink, E.; Cerantola, V.; Höppner, H.; Makita, M.; Pelka, A.; Prescher, C.; Sukharnikov, K.; Schmidt, A.; Thorpe, I.; Toncian, T.; Amouretti, A.; Chekrygina, D.; Falcone, R. W.; Falk, K.; Fletcher, L. B.; Galtier, E.; Harmand, M.; Hartley, N.; Hau-Riege, S. P.; Heimann, P.; Huang, L.; Humphries, O. S.; Karnbach, O.; Kraus, D.; Lee, H. J.; Nagler, B.; Ren, S.; Schuster, A.; Smid, M.; Voigt, K.; Zhang, M.; Zastrau, U.

The von Hámos spectrometer setup at the HED instrument of the European XFEL is described in detail. The spectrometer is designed to be operated primarily between 5 and 15 keV to complement the operating photon energy range of the HED instrument. Four Highly Annealed Pyrolitic Graphite (HAPG) crystals are characterised with thicknesses of 40 μm or 100 μm and radius-of-curvature 50 mm or 80 mm, in conjunction with either an ePix100 or Jungfrau detector. The achieved resolution with the 50 mm crystals, operated between 6.5 and 9 keV, matches that reported previously: ~8 eV for a thickness of 40 μm, whereas, with an 80 mm crystal of thickness 40 μm, the resolution exceeds that expected. Namely, a resolution of 2 eV is demonstrated between 5–6 keV implying a resolving power of 2800. Therefore, we posit that flatter HAPG crystals, with their high reflectivity and improved resolving power, are a powerful tool for hard x-ray scattering and emission experiments allowing unprecedented measurements of collective scattering in a single shot.

Permalink: https://www.hzdr.de/publications/Publ-32067
Publ.-Id: 32067


A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

Fuchs, M.; Beyer, J.; Lorenz, S.; Sharma, S.; Renno, A.; Heitmann, J.; Gloaguen, R.

With the recurring interest on rare-earth elements (REE), laser-induced fluorescence (LiF) may provide a powerful tool for their rapid and accurate identification at different stages along their value chain. Applications to natural materials such as rocks could complement the spectroscopy-based toolkit for innovative, non-invasive exploration technologies. However, the diagnostic assignment of detected emission lines to individual REE remains challenging, because of the complex composition of natural rocks in which they can be found. The resulting mixed spectra and the large amount of data generated demand for automated approaches of data evaluation, especially in mapping applications such as drill core scanning. LiF reference data provide the solution for robust REE identification, yet they usually remain in the form of tables of published emission lines. We show that a complete reference spectra library could open manifold options for innovative automated analysis.

We present a library of high-resolution LiF reference spectra using the Smithsonian rare-earth phosphate standards for electron microprobe analysis.We employ three standard laser wavelengths (325 nm, 442 nm, 532 nm) to record representative spectra in the UV-visible to near-infrared spectral range (340–1080 nm). Excitation at all three laser wavelengths yielded characteristic spectra with distinct REE-related emission lines for EuPO4, TbPO4, DyPO4 and YbPO4. In the other samples, the high-energy excitation at 325 nm caused unspecific, broadband defect emissions. Here, lower energy laser excitation showed successful for suppressing non-REE-related emission. At 442 nm excitation, REE-reference spectra depict the diagnostic emission lines of PrPO4, SmPO4 and ErPO4. For NdPO4 and HoPO4 most efficient excitation was achieved with 532 nm. Our results emphasise on the possibility of selective REE excitation by changing the excitation wavelength according to the suitable conditions for individual REEs. Our reference spectra provide a database for transparent and reproducible evaluation of REE-bearing rocks. The LiF spectral library is available at https://zenodo.org/ and the registered DOI: http://doi.org/10.5281/zenodo.4054606 (Fuchs et al., 2020). It gives access to traceable data for manifold further studies on comparison of emission line positions, emission line intensity ratios and splitting into emission line sub-levels or can be used as reference or training data for automated approaches of component assignment.

Keywords: Laser-induced fluorescence; rare earth elements; exploration; spectral library

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Permalink: https://www.hzdr.de/publications/Publ-32066
Publ.-Id: 32066


Drill-core mineral abundance estimation using hyperspectral and high-resolution mineralogical data

Tusa, L.; Khodadadzadeh, M.; Contreras Acosta, I. C.; Rafiezadeh Shahi, K.; Fuchs, M.; Gloaguen, R.; Gutzmer, J.

Due to the extensive drilling performed every year in exploration campaigns for the discovery and evaluation of ore deposits, drill-core mapping is becoming an essential step. While valuable mineralogical information is extracted during core logging by on-site geologists, the process is time consuming and dependent on the observer and individual background. Hyperspectral short-wave infrared (SWIR) data is used in the mining industry as a tool to complement traditional logging techniques and to provide a rapid and non-invasive analytical method for mineralogical characterization. Additionally, Scanning Electron Microscopy-based image analyses using a Mineral Liberation Analyser (SEM-MLA) provide exhaustive high-resolution mineralogical maps, but can only be performed on small areas of the drill-cores. We propose to use machine learning algorithms to combine the two data types and upscale the quantitative SEM-MLA mineralogical data to drill-core scale. This way, quasi-quantitative maps over entire drill-core samples are obtained. Our upscaling approach increases result transparency and reproducibility by employing physical-based data acquisition (hyperspectral imaging) combined with mathematical models (machine learning). The procedure is tested on 5 drill-core samples with varying training data using random forests, support vector machines and neural network regression models. The obtained mineral abundance maps are further used for the extraction of mineralogical parameters such as mineral association.

Keywords: hyperspectral imaging; drill-core; SWIR; mineral abundance mapping; mineral association; machine learning

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Permalink: https://www.hzdr.de/publications/Publ-32065
Publ.-Id: 32065


Object Detection Routine for Material Streams Combining RGB and Hyperspectral Reflectance Data Based on Guided Object Localization

Sudharshan, V.; Seidel, P.; Ghamisi, P.; Lorenz, S.; Fuchs, M.; Shaik Fareedh, J.; Neubert, P.; Schubert, S.; Gloaguen, R.

Electronic waste is the fastest growing type of scrap globally and is an important challenge due to its heterogeneity, intrinsic toxicity and potential environmental impact. With an objective of obtaining information on the composition of printed circuit boards (PCBs) through non-invasive analysis to aid in recycling and recovery of precious waste, the goal of this paper is to propose a scheme towards the fusion of RGB and hyperspectral data in object detection. State-of-art detectors come with their own set of challenges which make them inapplicable to PCB recycling. We introduce a method which promises to achieve object detection based on multi-sensor data by utilizing the hyperspectral data to localize components and compare the results to a conventional single-sensor (RGB) based approach.

Keywords: Object detection; Hyperspectral imaging; Recycling; Sensors; Spatial resolution; Training

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Permalink: https://www.hzdr.de/publications/Publ-32064
Publ.-Id: 32064


Sediment Transit Time and Floodplain Storage Dynamics in Alluvial Rivers Revealed by Meteoric 10Be

Repasch, M.; Wittmann, H.; Scheingross, J. S.; Sachse, D.; Szupiany, R.; Orfeo, O.; Fuchs, M.; Hovius, N.

Quantifying the time scales of sediment transport and storage through river systems is fundamental for understanding weathering processes, biogeochemical cycling, and improving watershed management, but measuring sediment transit time is challenging. Here we provide the first systematic test of measuring cosmogenic meteoric Beryllium‐10 (10Bem) in the sediment load of a large alluvial river to quantify sediment transit times. We take advantage of a natural experiment in the Rio Bermejo, a lowland alluvial river traversing the east Andean foreland basin in northern Argentina. This river has no tributaries along its trunk channel for nearly 1,300 km downstream from the mountain front. We sampled suspended sediment depth profiles along the channel and measured the concentrations of 10Bem in the chemically extracted grain coatings. We calculated depth‐integrated 10Bem concentrations using sediment flux data and found that 10Bem concentrations increase 230% from upstream to downstream, indicating a mean total sediment transit time of 8.4 ± 2.2 kyr. Bulk sediment budget‐based estimates of channel belt and fan storage times suggest that the 10Bem tracer records mixing of old and young sediment reservoirs. On a reach scale, 10Bem transit times are shorter where the channel is braided and superelevated above the floodplain, and longer where the channel is incised and meandering, suggesting that transit time is controlled by channel morphodynamics. This is the first systematic application of 10Bem as a sediment transit time tracer and highlights the method's potential for inferring sediment routing and storage dynamics in large river systems.

Keywords: meteoric 10Be; sediment transit time; river sediment; floodplains; sediment routing

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Permalink: https://www.hzdr.de/publications/Publ-32063
Publ.-Id: 32063


alpaka-group/alpaka: alpaka 0.5.0: C++14

Worpitz, B.; Matthes, A.; Zenker, E.; Hübl, A.; Widera, R.; Bastrakov, S.; Ehrig, S.; Kelling, J.; Krude, J.; Stephan, J.; Werner, M.

The alpaka library is a header-only C++14 abstraction library for accelerator development.
The release 0.5.0 is providing support for AMD HIP and dropped support for C++11, CUDA 8, gcc 4.9 and boost < 1.65.1.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: OS: Linux, Windows, or OSX requirements: C++14 compiler, boost 1.65.1+
    License: MPL-2.0
    Hosted on GitHub: Link to location
    DOI: 10.5281/zenodo.3909421

Permalink: https://www.hzdr.de/publications/Publ-32062
Publ.-Id: 32062


αvβ3-Specific Gold Nanoparticles for Fluorescence Imaging of Tumor Angiogenesis

Pretze, M.; von Kiedrowski, V.; Runge, R.; Freudenberg, R.; Hübner, R.; Davarci, G.; Schirrmacher, R.; Wängler, C.; Wängler, B.

This paper reports on the development of tumor-specific gold nanoparticles (AuNPs) as theranostic tools intended for target accumulation and the detection of tumor angiogenesis via optical imaging (OI) before therapy is performed, being initiated via an external X-ray irradiation source. The AuNPs were decorated with a near-infrared dye, and RGD peptides as the tumor targeting vector for αvβ3-integrin, which is overexpressed in tissue with high tumor angiogenesis. The AuNPs were evaluated in an optical imaging setting in vitro and in vivo exhibiting favorable diagnostic properties with regards to tumor cell accumulation, biodistribution, and clearance. Furthermore, the therapeutic properties of the AuNPs were evaluated in vitro on pUC19 DNA and on A431 cells concerning acute and long-term toxicity, indicating that these AuNPs could be useful as radiosensitizers in therapeutic concepts in the future.

Keywords: gold nanoparticle; optical imaging; radiosensitizer; tumor angiogenesis; RGD peptide

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Permalink: https://www.hzdr.de/publications/Publ-32061
Publ.-Id: 32061


Data for "Gold implanted germanium photoswitch for cavity dumping of a free-electron laser"

Rana, R.; Klopf, J. M.; Ciano, C.; Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.; Pashkin, O.

Measurements were carried out in ELBE 113 c lab. Free electron laser (FEL) pulses with a wavelength ranging from 6 to 90 µm from the FELBE laser operating at its maximum power level were used. Photoswitching of Ge and Ge:Au samples were carried out using a 1 kHz Ti:Sapphire Amplifier system at 800 nm. The data used in the paper is arranged in subfolders 1, 2, and 3. The description is as follows
1. Scheme of the experiment (used in Figure 1 and shows the idea of the experiment)
2. FEL pulse picking traces from photoswitched Ge and Ge: Au samples were recorded using an oscilloscope with 1 GHz bandwidth (Keysight InfiniiVision DSOX4104A).
Relevance: This data is used in Figures 2 and 3. This measurement showed the photoswitching attributes in both reflection and transmission geometry for the Ge and Ge: Au samples and suitability of Ge:Au sample for efficient cavity dumping.
3. Photoinduced reflectivity measurements for the Ge: Au sample as a function of the time delay between FEL pulses and the pulses from a kHz amplifier system is recorded. The fluence required to couple out FEL wavelengths with an efficiency of at least 50 % reflectivity and Matlab scripts used for simulation of photoinduced reflectivity for the same FEL wavelengths.
Relevance: This data is used in Figure 4 and shows the fluence requirements of the Ge:Au photoswitch and also a faster recovery time of sub-ns, much shorter than the FEL pulsing period of 77ns.

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Permalink: https://www.hzdr.de/publications/Publ-32060
Publ.-Id: 32060


A discussion of two-phase flow in the gas channel and porous transport layer regions of polymer electrolyte cells

Steven, S. B.; Andersson, M.; Weber, N.; Marschall, H.; Lehnert, W.

This talk is about an ongoing programme of research on detailed performance calculations for two-phase liquid-gas flow in the gas channel and porous transport layer, as found, for example, on the cathode side of a polymer electrolyte fuel cell. The porous geometry is typically obtained by digital reconstruction from nano-computer tomography images. The domain may then tessellated with a computational mesh, whereupon the equations of mass and momentum are solved ,e.g., by means of a volume-of-fluid method. Liquid water is produced at the same time as gaseous oxygen is consumed by electrochemical reduction at the electrode surface, which is to be considered a boundary condition in the present problem. The problem was originally formulated in ref. [1]. Liquid-gas counter flow in the porous transport layer results in liquid drops being entrained in co-flow in the gas channels and convected downstream by the gas. The flow in the channels and adjacent parts of the porous transport layer is transient-periodic, but with some significant randomness, associated with the interactions between the different fluid streams percolating into the channel from the pores.

In this presentation, the complex micro-scale flow field is described in some detail. Consideration is also given as to the mechanisms for construction of macro-homogeneous properties such as absolute and relative permeability, capillary pressure vs. saturation for porous media, as well as macroscopic drag laws for two-phase channel flows based on calculations on a micro-scale. These are required for macro-scale homogeneous models, as typically employed at a cell-level. A discussion is also given of the impact of salient physical properties such as surface tension, and how these may be manipulated to improve future performance for electrochemical conversion devices such as fuel cells and electrolysers.

  • Open Access Logo Lecture (Conference)
    I Meeting on Energy Conversion and Storage Electrochemical Devices, 28.-29.01.2021, Madrid, Spanien

Permalink: https://www.hzdr.de/publications/Publ-32058
Publ.-Id: 32058


Theory of three-magnon interaction in a vortex-state magnetic nanodot

Verba, R.; Körber, L.; Schultheiß, K.; Schultheiß, H.; Tiberkevich, V.; Slavin, A.

This repository contains the data used to determine the numerical threshold fields for three-magnon scattering in a vortex-state disk used in our paper "Theory of three-magnon interaction in a vortex-state magnetic nanodot" published in Physical Review B. 

For different excitation frequencies, we provide:

  • mumax3 simulation file and table containing the time-dependent magnetic energy for simulations where the microwave-field power is decreased over time
  • mumax3 file and resulting power spectrum for a continuous-wave excitation at a given microwave-field power above threshold
  • spatial mode profiles (magnitude/amplitude) to identify the modes taking part in the three-magnon splitting channel

Keywords: spin wave; theory; nonlinear; vortex; micromagnetic simulation

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Permalink: https://www.hzdr.de/publications/Publ-32057
Publ.-Id: 32057


The Spatial Association of Accessory Minerals with Biotite in Granitic Rocks

Clarke, B. D.; Renno, A.; Hamilton, D. C.; Gilbricht, S.; Bachmann, K.

We use mineral liberation analysis (MLA) to quantify the spatial association of 15118 grains of accessory apatite, monazite, xenotime, and zircon with essential biotite, and clustered with themselves, in a peraluminous biotite granodiorite from the South Mountain Batholith in Nova Scotia. A random distribution of accessory minerals demands that the proportion of accessory minerals in contact with biotite is identical to the proportion of biotite in the rock, and the binary touching factor (percentage of accessory mineral touching biotite divided by modal proportion of biotite) would be ~1.00. Instead, the mean binary touching factors for the four accessory minerals in relation to biotite are: apatite (5.06 for 11168 grains), monazite (4.68 for 857 grains), xenotime (4.36 for 217 grains), and zircon (5.05 for 2876 grains). Shared perimeter factors give similar values. Monazite and zircon have approximately log-normal grain-size distributions, but apatite is strongly skewed toward larger grain sizes, and xenotime is skewed toward smaller grain sizes. Accessory mineral grains that straddle biotite grain boundaries are larger than completely locked, or completely liberated, accessory grains. Only apatite-monazite clusters are significantly more abundant than expected for random distribution. The high, and statistically significant, binary touching factors and shared perimeter factors suggest a strong physical or chemical control on their spatial association. We evaluate random collisions in magma (synneusis), heterogeneous nucleation processes, induced nucleation in passively enriched boundary layers, and induced nucleation in actively enriched boundary layers to explain the significant touching factors. All processes operate during the crystallization history of the magma, but induced nucleation in passively and actively enriched boundary layers are most likely to explain the strong spatial association of phosphate accessories and zircon with biotite. In addition, at least some of the apatite and zircon may also enter the granitic magma as inclusions in grains of Ostwald-ripened xenocrystic biotite.

Keywords: accessory minerals; biotite; spatial association; boundary layer; synneusis; heterogeneous nucleation

Permalink: https://www.hzdr.de/publications/Publ-32056
Publ.-Id: 32056


Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer

Kowalska, E.; Sluka, V.; Kakay, A.; Fowley, C.; Lindner, J.; Fassbender, J.; Deac, A. M.

Here, we present an analytical and numerical model describing the magnetization dynamics in MgO-based spin-torque nano-oscillators with an in-plane magnetized polarizer and an out-of-plane free layer. We introduce the spin-transfer torque asymmetry by considering the cosine angular dependence of the magnetoresistance between the two magnetic layers in the stack. For the analytical solution, dynamics are determined by assuming a circular precession trajectory around the direction perpendicular to the plane, as set by the effective field, and calculating the energy integral over a single precession period. In a more realistic approach, we include the bias dependence of the tunnel magnetoresistance, which is assumed empirically to be a piecewise linear function of the applied voltage. The dynamical states are found by solving the stability condition for the Jacobian matrix for out-of-plane static states. We find that the bias dependence of the tunnel magnetoresistance, which is an inseparable effect in every tunnel junction, exhibits drastic impact on the spin-torque nano-oscillator phase diagram, mainly by increasing the critical current for dynamics and quenching the oscillations at high currents. The results are in good agreement with our experimental data published elsewhere.

Keywords: spin-torque nano-oscillator (STNO); MgO-based magnetic tunnel junctions; tunnel magnetoresistance

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Permalink: https://www.hzdr.de/publications/Publ-32055
Publ.-Id: 32055


Multi-Feature Treatment Verification in Particle Therapy

Kögler, T.; Alagoz, E.; Beyer, R.; Hammer, S.; Hysing, L. B.; Lutz, B.; Meric, I.; Permatasari, F.; Pettersen, H. E. S.; Römer, K.; Schellhammer, S.; Skjerdal, K.; Turko, J. A. B.; Wagner, A.; Weinberger, D.; Werner, R.-D.; Ytre-Hauge, K.; Pausch, G.

Particle therapy constitutes a promising and rapidly developing method in modern cancer treatment. In order to exploit its full potential, however, it requires detailed dose verification.
Although the applicability of in-beam positron emission tomography and prompt gamma rays has already been demonstrated in patients, range verification is not yet part of the clinical routine in particle therapy. This is due to not only the methodological limitations of previous systems, but also to commercial, clinical and physical boundary conditions.
In pencil beam scanning, the state-of-the-art treatment method in particle therapy, the number of secondary particles (essentially positrons, prompt gamma rays and fast neutrons) available per spot (Δt = 10 ms to 100 ms) is limited. This leads to statistical accuracy limits for verification systems exploiting these secondary particles as range probes. The development of a clinically useable treatment verification system requires gathering as much information about the local dose, as possible.
The instantaneous fluence rate of prompt gamma rays reaching 5×10⁶ cm‾²s‾¹ to 10⁸ cm‾²s‾¹ challenges modern data acquisitions connected to monolithic inorganic scintillators with typical sizes used in present verification systems. In order to reduce the detector load, and also with regard to the ever higher intensities of next generation medical accelerators, future systems have to be more granular.
Multi-Feature Treatment Verification combines and extends established methods (prompt gamma-ray imaging, spectroscopy, timing, etc.) in order to achieve higher reliability and performance. This idea was taken up by the NOVO project and expanded by a multi-particle approach. The NOVO (i.e. N eutron and gamma ray imaging with quasi-monolithic organic detector arrays – a novel, holistic approach to real-time range assessment-based treatment verification in particle therapy) consortium is a large collaboration of medical, nuclear and detector physicists, nuclear engineers, and mathematicians, which aim to develop a holistic realtime treatment verification system in particle therapy.
Elements of a potential multi-feature/multi-particle treatment verification multi-channel system were characterized in a double time-of-flight experiment at the pulsed photo-neutron source nELBE (neutrons @ Electron Linac for beams with high Brilliance and low Emittance). The essential properties (time resolution, light yield, detection efficiency and pulse shape discrimination) of an EJ-276 plastic scintillator were determined. The very first experimental results show that the time resolution (ΔT < 400 ns) of a 20 × 20 × 200 mm³
EJ-276 plastic scintillator with double-sided readout will reach the high demands of such a proposed range verification system. However, the determined quality of the pulse-shape discrimination, the energy resolution and the quite high neutron detection threshold of above 200 keV show that the light yield of this type of scintillator is not high enough to be used in a multi-feature-based treatment verification system. Particle transport calculations with MCNP6 and GEANT4 were performed to confirm the experimental results of a single detector element. Furthermore, they also show a promising measurement accuracy of a multi-channel overall system.

Keywords: particle therapy; treatment verification; in-vivo range assessment; NOVO project

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  • Lecture (Conference)
    The 7th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, 21.-25.06.2021, Praha, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-32054
Publ.-Id: 32054


A Roadmap for 3D Metal Aerogels: Materials Design and Application Attempts

Jiang, X.; Du, R.; Hübner, R.; Hu, Y.; Eychmüller, A.

Armed with merits of the metals (e.g., electrical conductivity, catalytic activity, and plasmonic properties) and aerogels (e.g., monolithic structure, porous network, and large specific surface area), metal aerogels (MAs) have stood out as a new class of porous materials in the last decade. With unparalleled potential in electrocatalysis, plasmonics, and sensing, they are envisaged to revolutionize the energy- and detection-related application fields. However, MA development is severely retarded by the lack of a sufficient material basis. Suffering from the ambiguous understanding of formation mechanisms, big challenges remain for tailoring MAs for task-specific applications. By surveying state-of-the-art developments, this review strives to summarize design principles and arouse interest in broad scientific communities. Moreover, critical challenges and opportunities are highlighted to provide a research roadmap for this young yet promising field.

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Permalink: https://www.hzdr.de/publications/Publ-32053
Publ.-Id: 32053


Multi-particle detection and imaging with quasi-monolithic organic detector arrays for treatment verification in particle therapy

Alagoz, E.; Hammer, S.; Hysing, L. B.; Kögler, T.; Pausch, G.; Pettersen, H. E. S.; Skjerdal, K.; Ytre-Hauge, K.; Meric, I.

Particle therapy is a modality for treating cancer using ionizing radiation from, e.g., protons or carbon ions. A growing number of patients worldwide receive particle therapy as a part of their cancer treatment due to its dosimetric advantages over the more conventional external beam radiotherapy using photons. The finite range of particles in tissue results in sparing of healthy tissue surrounding the tumour and thereby a reduced risk of adverse effects compared to conventional treatment. This opens possibilities for a more intensified treatment by dose escalation to the tumour and thereby an increased probability for controlling the disease. However, charged particles, when used for external beam radiotherapy, are much less forgiving than photons in case of treatment deviations. Treatment deviations may be caused by (1) sensitivity of charged particles to anatomical or density changes along their radiological path in the patient, e.g., due to organ motion or tumour shrinkage and (2) uncertainties associated with the estimation of the exact position of the Bragg-peak
(maximum dose deposition) in tissue, e.g., due to uncertainties in the estimation of stopping power ratios. Collectively, these are referred to as “range uncertainties”. The most important consequence of range uncertainties is that the tissue sparing potential of charged particles cannot be fully exploited. Therefore, there is an urgent need for reliable and robust treatment verification systems that can identify potential treatment deviations in real-time.

Despite recent advances in state-of-the-art prompt gamma-ray imaging, spectroscopy and timing systems as well as in-beam and offline PET imaging systems, the development of treatment verification systems still lags and as such, there is no system yet in wide routine clinical use. Common to all existing solutions is the fact that they rely on a single feature of a single particle species and will therefore suffer from limited counting statistics. This is an important limiting factor in applying state-of-the-art systems in a treatment verification system.
Recently, a collaboration of detector, nuclear and medical physicists, nuclear engineers and mathematicians initiated the NOVO (Neutron and gamma-ray imaging with quasi-monolithic organic detector arrays – a novel, holistic approach to real-time range assessment-based treatment verification in particle therapy) project. The aim of the NOVO project is to develop a sophisticated quasi-monolithic organic detector array (QuDA) that will combine detection and imaging of secondary fast neutrons and prompt gamma-rays produced in nuclear interactions of incident particles with tissue, the profiles of which show a strong correlation with the incident particle beam range. In addition to imaging spatial profiles of secondary fast neutrons and prompt gammarays,
the QuDA will be used to acquire information on additional features of each particle species, such as timing, energy and intensity, that can provide supplementary information on the range of particle beams in tissue, thus representing a major shift from single-feature, single-particle systems to a multi-feature, multiparticle system.
In this contribution we will report on first estimates of the imaging properties of a potential QuDA design, based on Monte Carlo radiation transport models with MCNP6.2, Geant4 and GATE, considering fast neutrons and prompt gamma-rays for various, realistic combinations of timing, energy and position resolution of the individual sensing elements. Furthermore, we will report on the expected detection efficiencies and the resulting range monitoring precision for proton beams with clinically relevant energies and intensities incident on homogeneous polymethyl methacrylate phantoms. The preliminary results demonstrate the potential to obtain a range monitoring precision of approximately 1 mm down to proton beam intensities of about 1 – 2 x
10⁷ [protons/pencil beam] when fast neutron and prompt gamma-ray data are combined.

Keywords: proton therapy; treatment verification; range assesment; organic detector arrays

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  • Lecture (Conference)
    The 7th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, 21.-25.06.2021, Praha, Tschechien

Permalink: https://www.hzdr.de/publications/Publ-32052
Publ.-Id: 32052


Where2Test: Identifying optimal spatiotemporal testing policies for mitigating the shortage of SARS-CoV-2 testing capacity

Calabrese, J.

A poster giving an overview of the Where2Test project and its core goals and methods.

  • Poster
    Visit of the Polish Delegation to CASUS, 29.09.2020, CASUS, Germany

Permalink: https://www.hzdr.de/publications/Publ-32051
Publ.-Id: 32051


Where2Test: Spatiotemporal, multifactor optimization of COVID-19 testing strategies

Calabrese, J.; Bussmann, M.

We give an overview of the Where2Test project, focusing on the general approach and particular applications for machine learning.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Artificial Intelligence for a better living: medicine, science-business, 30.09.2020, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-32050
Publ.-Id: 32050


Magnetic Field Assisted Electrodeposition of Metal on Conically Structured Electrodes

Huang, M.; Eckert, K.; Mutschke, G.

Conical structures towards nanometer length scales are attractive for numerous applications including super-hydrophobic and electrocatalytic materials. Among the various methods of synthesizing arrays of micro- and nano-cones, electrochemical deposition techniques have been widely applied. We aim at enhancing the conical growth during deposition by applying an external magnetic field. Most of the magnetic field effects can be attributed to the Lorentz force and the magnetic gradient force [1]. If the magnetic field imposed on the electrochemical cell is well designed, the magnetic forces can generate an electrolyte flow which brings fresh electrolyte towards the tip of a cone, so that the local mass transfer would be enhanced and the conical growth would be supported.

We first performed analytical and numerical studies of electrodeposition on diamagnetic (Cu) and ferromagnetic (Fe) cones of mm size under the influence of a homogeneous vertical magnetic field. The beneficial structuring effects of the Lorentz force has already been shown for the Cu cone case [2]. The magnetization of the Fe cones causes additionally a strong magnetic gradient force near the cone tips and gives rise to a flow that can bring enriched electrolyte to the conical cathode. As the cathodes are placed at the bottom of the electrochemical cell, solutal buoyancy tends to bring upwards lighter electrolyte from the conical cathode and thus counteract the downward flow caused by the magnetic forces. Our results show that for the Cu cones, the Lorentz force becomes smaller than the buoyancy force after the first few seconds of the deposition, while the magnetic gradient force in case of the Fe cones keeps surpassing the buoyancy during the deposition.

Next, scaling studies on cones of sizes ranging from millimeter to micrometer allow to deliver insights into the magnetic field assisted electrodeposition towards micro- and nano-cones. As the cone size shrinks, the geometrical inhomogeneity decreases, and the current density gets more uniformly distributed on the cone, which is making the conical growth more difficult. Furthermore, the beneficial flow forced by the magnetic field near smaller cones suffers from higher wall friction. But this can be partially compensated by the larger magnetic gradients existing at smaller Fe cones, and the flow caused by the magnetic gradient force was found to decrease more slowly than the flow caused by other forces with the decreasing cone size. Such scaling behavior of the flow velocity corresponds well with a theoretical analysis of the Navier-Stokes equation. For a Fe cone with a radius of 10 micron under study here, the magnetic gradient force generates a beneficial downward flow with a velocity of about 5 micron per second. But in general the structuring effects during the deposition is much weaker than at larger length scales.

This work shows the potential of using the magnetic gradient force for growing ferromagnetic conical structures during electrodeposition. Optimization possibilities for conical growth at smaller scales by e.g. enhancing the cell current, applying stronger magnetic fields and pulsed electrodeposition will also be discussed.

Permalink: https://www.hzdr.de/publications/Publ-32049
Publ.-Id: 32049


How range residency and long-range perception change encounter rates

Martinez-Garcia, R.; Fleming, C. H.; Seppelt, R.; Fagan, W. F.; Calabrese, J.

Encounter rates link movement strategies to intra- and inter-specific interactions, and therefore translate individual movement behavior into higher-level ecological processes. Indeed, a large body of interacting population theory rests on the law of mass action, which can be derived from assumptions of Brownian motion in an enclosed container with exclusively local perception. These assumptions imply completely uniform space use, individual home ranges equivalent to the population range, and encounter dependent on movement paths actually crossing. Mounting empirical evidence, however, suggests that animals use space non-uniformly, occupy home ranges substantially smaller than the population range, and are of- ten capable of nonlocal perception. Here, we explore how these empirically supported behaviors change pairwise encounter rates. Specifically, we derive novel analytical expressions for encounter rates under Ornstein-Uhlenbeck motion, which features non-uniform space use and allows individual home ranges to differ from the population range. We compare OU-based encounter predictions to those of Reflected Brownian Motion, from which the law of mass action can be derived. For both models, we further explore how the interplay between the scale of perception and home-range size affects encounter rates. We find that neglecting realistic movement and perceptual behaviors can lead to systematic, non-negligible biases in encounter-rate predictions.

Keywords: Ecological theory; Encounter rates; Movement ecology; Home ranges

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Permalink: https://www.hzdr.de/publications/Publ-32048
Publ.-Id: 32048


How optimal allocation of limited testing capacity changes epidemic dynamics

Calabrese, J.; Demers, J.

Insufficient testing capacity continues to be a critical bottleneck in the worldwide fight against COVID-19. Optimizing the deployment of limited testing resources has therefore emerged as a keystone problem in pandemic response planning. Here, we use a modified SEIR model to optimize testing strategies under a constraint of limited testing capacity. We define pre-symptomatic, asymptomatic, and symptomatic infected classes, and assume that positively tested individuals are immediately moved into quarantine. We further define two types of testing. Clinical testing focuses only on the symptomatic class. Non-clinical testing detects pre- and asymptomatic individuals from the general population, and an information parameter governs the degree to which such testing can be focused on high infection risk individuals. We then solve for the optimal mix of clinical and non-clinical testing as a function of both testing capacity and the information parameter. We find that purely clinical testing is optimal at very low testing capacities, supporting early guidance to ration tests for the sickest patients.
Additionally, we find that a mix of clinical and non-clinical testing becomes optimal as testing capacity increases. At high but empirically observed testing capacities, a mix of clinical testing and unfocused (information=0) non-clinical testing becomes optimal. We further highlight the dvantages of early implementation of testing programs, and of combining optimized testing with contact reduction interventions such as lockdowns, social distancing, and masking.

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Permalink: https://www.hzdr.de/publications/Publ-32047
Publ.-Id: 32047


Formation of spiral waves in cylindrical containers under orbital excitation

Horstmann, G. M.; Anders, S.; Kelley, D.; Weier, T.

The lowest swirling wave mode arising in upright circular cylinders as a response to orbital excitation has been widely studied in the last decade, largely owing to its high practical relevance for orbitally shaken bioreactors. Our recent theoretical study (Horstmann et al. 2020) revealed a damping-induced symmetry breaking mechanism that can cause spiral wave structures manifested in the so far widely disregarded higher rotating wave modes. Building on this work, we develop a spiralisation criterion and classify different spiral regimes as a function of the most relevant dimensionless groups. The analysis suggests that high Bond numbers and shallow liquid layers favour the formation of coherent spiral waves. This result paved the way to find the predicted wave structures in our interfacial sloshing experiment. We present two sets of experiments, with different characteristic damping rates, verifying the formation of both coherent and overdamped spiral waves in conformity with the theoretical predictions.

Permalink: https://www.hzdr.de/publications/Publ-32046
Publ.-Id: 32046


Impact of high pressure torsion processing on helium ion irradiation resistance of molybdenum

Krawczyńska, A. T.; Ciupiński, Ł.; Gloc, M.; Setman, D.; Spychalski, M.; Suchecki, P.; Adamczyk-Cieślak, B.; Liedke, M. O.; Butterling, M.; Wagner, A.; Hirschmann, E.; Petersson, P.

The microstructure of molybdenum mirrors was refined by high pressure torsion. Already after one rotation microhardness significantly increased from 231 for the as-received mirror to 542 HV0.2. The increase of number of rotations to five caused further slight increase of microhardness to 558 HV0.2. The higher microhardness values correspond well with the grain refinement as the grain size decreased with the increase of the deformation degree down to 480 and 110 nm, respectively for 1 and 5 rotations. Subsequently, refined mirrors and a reference micrograined one were irradiated by He ions to the dose of 8x1016/cm 2 to simulate the effect of plasma exposure on diagnostic mirrors to be applied in D-T fusion devices. Irradiations were followed by reflectivity measurements in the 300-2400 nm range with a dual beam spectrometer. It was noticed that irradiation caused a slight decrease in total reflectivity of the micrograined mirror, whereas that of high-pressure torsion-processed samples decreases by an additional 2.5%. Nanohardness measurements, detailed microscopy observations using focused ion beam and scanning transmission electron microscope as well as positron annihilation spectroscopy investigations were performed to elucidate that cause of those changes. Based on the results, it is postulated that the nanocracks created at grain boundaries during irradiation in the optically active layer are responsible for lower reflectivity of high-pressure torsion-processed mirrors.

Keywords: nanomaterials; ion irradiation; electron microscopy; vacancy; severe plastic deformation; positron annihilation spectroscopy; PALS

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  • Secondary publication expected from 23.07.2023

Permalink: https://www.hzdr.de/publications/Publ-32045
Publ.-Id: 32045


Autonomous implementation of thermodynamic cycles at the nanoscale

Strasberg, P.; Wächtler, C. W.; Schaller, G.

There are two paradigms to study nanoscale engines in stochastic and quantum thermodynamics.
Autonomous models, which do not rely on any external time-dependence, and models that make use of time-dependent control fields, often combined with dividing the control protocol into idealized strokes of a thermodynamic cycle. While the latter paradigm offers theoretical simplifications, its utility in practice has been questioned due to the involved approximations. Here, we bridge the two paradigms by constructing an autonomous model, which implements a thermodynamic cycle in a certain parameter regime. This effect is made possible by self-oscillations, realized in our model by the well studied electron shuttling mechanism. Based on experimentally realistic values, we find that a thermodynamic cycle analysis for a single-electron working fluid is unrealistic, but already a few-electron working fluid could suffice to justify it. We also briefly discuss additional open challenges to autonomously implement the more studied Carnot and Otto cycles.

Keywords: thermodynamic cycle; self-oscillation; autonomous control; electron shuttle

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Permalink: https://www.hzdr.de/publications/Publ-32044
Publ.-Id: 32044


Spin stress contribution to the lattice dynamics of FePt

von Reppert, A.; Willig, L.; Pudell, J.-E.; Zeuschner, S.; Sellge, G.; Ganss, F.; Hellwig, O.; Ander Arregi, J.; Uhlíř, V.; Crut, A.; Bargheer, M.

Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments. We show that the granular microstructure is essential to support the contractive out-of-plane stresses originating from in-plane expansion via the Poisson effect that add to the uniaxial contractive stress driven by spin disorder. We prove the spin contribution by saturating the magnetic excitations with a first laser pulse and then detecting the purely expansive response to a second pulse. The contractive spin stress is reestablished on the same 100-ps time scale that we observe for the recovery of the ferromagnetic order. Finite-element modeling of the mechanical response of FePt nanosystems confirms the morphology dependence of the dynamics.

Permalink: https://www.hzdr.de/publications/Publ-32043
Publ.-Id: 32043


Theory of three-magnon interaction in a vortex-state magnetic nanodot

Verba, R.; Körber, L.; Schultheiß, K.; Schultheiß, H.; Tiberkevich, V.; Slavin, A.

We use vector Hamiltonian formalism (VHF) to study theoretically three-magnon parametric interaction (or three-wave splitting) in a magnetic disk existing in a magnetic vortex ground state. The three-wave splitting in a disk is found to obey two selection rules: (i) conservation of the total azimuthal number of the resultant spin-wave modes, and (ii) inequality for the radial numbers of interacting modes, if the mode directly excited by the driving field is radially symmetric (i.e. if the azimuthal number of the directly excited mode is m=0). The selection rule (ii), however, is relaxed in the "small" magnetic disks, due to the influence of the vortex core. We also found, that the efficiency of the three-wave interaction of the directly excited mode strongly depends on the azimuthal and radial mode numbers of the resultant modes, that becomes determinative in the case when several splitting channels (several pairs of resultant modes) simultaneously approximately satisfy the resonance condition for the splitting. The good agreement of the VHF analytic calculations with the experiment and micromagnetic simulations proves the capability of the VHF formalism to predict the actual splitting channels and the magnitudes of the driving field thresholds for the three-wave splitting.

Keywords: spin wave; nonlinear; three-magnon interaction; theory; micromagnetic simulation; vortex

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Permalink: https://www.hzdr.de/publications/Publ-32042
Publ.-Id: 32042


Circular by Design (CbD) - Ressourcenwende über nachhaltiges Produktdesign am Fallbeispiel Kühl-/Gefriergeräte

Raatz, S.; Heibeck, M.; Bickel, M.; Liedtke, C.; Tochtrop, C.; Schliack, M.; Förster, S.; Wächter, M.; Irmer, J.

Das Ziel von „Circular by Design“ besteht in der Entwicklung eines kreislauffähigen Produktdesigns für Kühl-/Gefriergeräte, das neben Energieeffizienz auch auf Ressourceneffizienz hin optimiert ist. Mit dem durch das BMBF geförderten Projekt soll die tatsächlich machbare Umsetzung von zirkulärem Design, zum einen mit dem Fokus auf Repair/Reuse und zum anderen auf möglichst geschlossene Recyclingpfade, demonstriert werden.
Die Zusammenführung der Ressourceneffizienzanalyse mit dem technologieorientierten und simulationsbasierten „Design for Recycling“-Modell soll künftig die Vorhersage eines für eine vollständige Kreislaufführung geeigneten Produktdesigns erlauben. Es werden die derzeitigen Verluste beim Erfassen und Recycling eines Kühl-/Gefriergerätes auf verschiedenen Ebenen quantifiziert, Ressourceneffizienzpotentiale dargestellt und auf dieser Basis ein Produktdesign entwickelt, dessen Materialzusammensetzung ein möglichst vollständiges Recycling sowie Reuse erlaubt.

Keywords: Recyclingfähigkeit; zirkuläres Produktdesign; metallische Rohstoffe; Ressourceneffizienz; Kreislaufwirtschaft; Kühl-/Gefriergeräte; Nachhaltigkeit; Substitution; Sekundäre Rohstoffe

  • Contribution to proceedings
    Recy & DepoTech 2020, 18.-20.11.2020, Leoben, Österreich
    Circular by Design (CbD) - Ressourcenwende über nachhaltiges Produktdesign am Fallbeispiel Kühl-/Gefriergeräte, Wien: aVW Abfallverwertungstechnik & Abfallwirtschaft, 978-3-200-07190-2, 799-804

Permalink: https://www.hzdr.de/publications/Publ-32041
Publ.-Id: 32041


Strongly coupled electron liquid: Ab initio path integral Monte Carlo simulations and dielectric theories

Dornheim, T.; Sjostrom, T.; Tanaka, S.; Vorberger, J.

Data used in the paper

Strongly coupled electron liquid: Ab initio path integral Monte Carlo simulations and dielectric theories

Tobias Dornheim, Travis Sjostrom, Shigenori Tanaka, and Jan Vorberger

Phys. Rev. B 101, 045129 – Published 27 January 2020

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Permalink: https://www.hzdr.de/publications/Publ-32038
Publ.-Id: 32038


Mapping the Structure of Oxygen-Doped Wurtzite Aluminum Nitride Coatings From Ab Initio Random Structure Search and Experiments

Gasparotto, P.; Fischer, M.; Scopece, D.; Liedke, M. O.; Butterling, M.; Wagner, A.; Yildirim, O.; Trant, M.; Passerone, D.; Hug, H. J.; Pignedoli, C. A.

Machine learning is changing how we design and interpret experiments in materials science. In this work we show how unsupervised learning, combined with ab initio random structure searching, improves our understanding of structural metastability in multicomponent alloys. We focus on the case of Al-O-N alloys where the formation of aluminum vacancies in wurtzite AlN upon the incorporation of substitutional oxygen can be seen as a general mechanism of solids where crystal symmetry is reduced to stabilize defects. The ideal AlN wurtzite crystal structure occupation cannot be matched due to the presence of an aliovalent hetero-element into the structure. The traditional interpretation of the c-lattice shrinkage in sputter-deposited Al-O-N films from X-ray diffraction (XRD) experiments suggests the existence of a solubility limit at 8 at.% oxygen content. Here we show that such naive interpretation is misleading. We support XRD data with accurate ab initio modeling and dimensionality reduction on advanced structural descriptors to map structure-property relationships. No signs of a possible solubility limit are found. Instead, the presence of a wide range of non-equilibrium oxygen-rich defective structures emerging at increasing oxygen contents suggests that the formation of grain boundaries is the most plausible mechanism responsible for the lattice shrinkage measured in Al-O-N sputtered films. We further confirm our hypothesis using positron annihilation lifetime spectroscopy.

Keywords: machine learning; ab initio; AlN; vacancy; defects; positron annihilation spectroscopy; XRD; PALS

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Permalink: https://www.hzdr.de/publications/Publ-32037
Publ.-Id: 32037


New instrumentation to enable novel imaging modalities using sub-50 keV transmitted helium ions

Mousley, M.; Eswara, S.; de Castro, O.; Bouton, O.; Serralta Hurtado De Menezes, E.; Klingner, N.; Koch, C.; Hlawacek, G.; Wirtz, T.

Helium ions offer an alternative imaging probe to electrons, with a smaller de Broglie wavelength at the same energy [1] [2][3]. Furthermore, the ability for neutralisation means that images can be formed by collecting only post-sample neutrals or both neutrals and transmitted ions. A comparison between the two can map where ions are more easily neutralised and offers an alternative contrast mechanism not possible with electrons. Transmission helium ion imaging is quite an understudied field and more experiments are required to fully assess the possibilities and benefits with this new microscopy. With this aim in mind, a prototype transmission helium ion microscope (THIM) has been constructed at the Luxembourg -Institute of Science and Technology (LIST) (Figure 1). The ion source is a duoplasmatron operated at 10-20 keV with a minimum beam spot size of 100 µm and a beam current of 0.1-2 nA . A microchannel plate (MCP) located behind the sample converts the transmitted ion signal to an electron shower which then hits a phosphor screen for direct transmission imaging with a stationary beam [4]. The detector is placed over 50 cm away from the sample. Imaging of crystalline powders showed unexpectedly large charging and deformation of the beam, producing collections of spots (Figure 2). Scanning transmission ion microscopy (STIM) can also be conducted if the phosphor screen is replaced with a metal anode plate. As the beam is scanned over the sample surface, the current from the plate is measured and gives the intensity at each pixel in the STHIM image. A secondary electron detector in front of the sample is used to record secondary electron images at the same time as STIM imaging (Figure 1). Post sample deflectors blank all ions in transmission, such that only neutral atoms are imaged and the fraction of neutralised ions can be estimated. Electrostatic blanking and using the anode plate current as a stop signal allows one to determine the energy of transmitted particles by measuring their time of flight (TOF). In addition, a position sensitive delay line detector has recently been installed, to add position sensitivity to the TOF measurements. This allows both the trajectory and energy of and ion to be measured at the same time, providing a more complete record of the transmission through the sample.

On a separate prototype machine, the ‘NPScope’ instrument, which combines a gas field ion source with a transmission delay line detector, STIM can be performed with nanometre spot size. This enables parallel bright and dark field imaging using the same detector (Figure 3).

Keywords: helium ion imaging; Scanning transmission ion microscopy

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  • Lecture (Conference) (Online presentation)
    Virtual Early Career European Microscopy Congress 2020, 24.-26.11.2020, København, Danmark

Permalink: https://www.hzdr.de/publications/Publ-32036
Publ.-Id: 32036


Gold implanted germanium photoswitch for cavity dumping of a free-electron laser

Rana, R.; Klopf, J. M.; Ciano, C.; Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.; Pashkin, O.

We present a plasma switch based on gold implanted germanium (Ge:Au) as a potential candidate for efficient cavity dumping of a free-electron laser (FEL). Ge:Au has a sub-nanosecond carrier lifetime – much shorter than the FEL pulsing period of 77 ns – and demonstrates a high photoinduced reflectivity in a broad range of infrared wavelengths from 6 to 90 µm. The Ge:Au plasma switch exhibits negligible absorption of the FEL radiation in the ʻoff ʼ state and requires only moderate thermoelectric cooling for incident FEL power of several Watts. A reflectivity level of more than 50 % in the ‘on’ state is achieved over the entire spectral range of this study. The corresponding optical pump fluence exhibits a linear relationship with the FEL frequency. This scaling is corroborated by our simulations highlighting the role of a finite sub-µm thickness of the photoinduced reflecting plasma layer. The demonstrated device is promising for the realization of the FEL cavity dumping for experiments that simultaneously require higher pulse energy and lower average power.

Keywords: Intense Terahertz pulses; Free Electron Laser; Cavity dumping; Optical switch

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Permalink: https://www.hzdr.de/publications/Publ-32035
Publ.-Id: 32035


Data for "Observation of strong magneto plasmonic nonlinearity in bilayer graphene discs"

Chin, M. L.; Matschy, S.; Stawitzki, F.; Poojali, J.; Hafez, H. A.; Turchinovich, D.; Winnerl, S.; Kumar, G.; Myers-Ward, R. L.; Dejarld, M. T.; Daniels, K. M.; Drew, H. D.; Murphy, T. E.; Mittendorff, M.

Data, Labbook notes and some presentations to the pblication topic

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Permalink: https://www.hzdr.de/publications/Publ-32034
Publ.-Id: 32034


Data for: Fusion of Dual Spatial Information for Hyperspectral Image Classification

Duan, P.; Ghamisi, P.; Kang, X.; Rasti, B.; Li, S.; Gloaguen, R.

The inclusion of spatial information into spectral classifiers for fine-resolution hyperspectral imagery has led to significant improvements in terms of classification performance. The task of spectral-spatial hyperspectral image classification has remained challenging because of high intraclass spectrum variability and low interclass spectral variability. This fact has made the extraction of spatial information highly active. In this work, a novel hyperspectral image classification framework using the fusion of dual spatial information is proposed, in which the dual spatial information is built by both exploiting pre-processing feature extraction and post-processing spatial optimization. In the feature extraction stage, an adaptive texture smoothing method is proposed to construct the structural profile (SP), which makes it possible to precisely extract discriminative features from hyperspectral images. The SP extraction method is used here for the first time in the remote sensing community. Then, the extracted SP is fed into a spectral classifier. In the spatial optimization stage, a pixel-level classifier is used to obtain the class probability followed by an extended random walker-based spatial optimization technique. Finally, a decision fusion rule is utilized to fuse the class probabilities obtained by the two different stages. Experiments performed on three data sets from different scenes illustrate that the proposed method can outperform other state-of-the-art classification techniques. In addition, the proposed feature extraction method, i.e., SP, can effectively improve the discrimination between different land covers.

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Permalink: https://www.hzdr.de/publications/Publ-32033
Publ.-Id: 32033


Data for: Remote Sensing Image Classification Using Subspace Sensor Fusion

Rasti, B.; Ghamisi, P.

The amount of remote sensing and ancillary datasets captured by diverse airborne and spaceborne sensors has been tremendously increased, which opens up the possibility of utilizing multimodal datasets to improve the performance of processing approaches with respect to the application at hand. However, developing a generic framework with high generalization capability that can effectively fuse diverse datasets is a challenging task since the current approaches are usually only applicable to two specific sensors for data fusion. In this paper, we propose an accurate fusion-based technique called SubFus with capability to integrate diverse remote sensing data for land cover classification. Here, we assume that a high dimensional multisensor dataset can be represented fused features that live in a lower-dimensional space. The proposed classification methodology includes three main stages. First, spatial information is extracted by using spatial filters (i.e., morphology filters). Then, a novel low- rank minimization problem is proposed to represent the multisensor datasets in subspaces using fused features. The fused features in the lower-dimensional subspace are estimated using a novel iterative algorithm based on the alternative direction method of multipliers. Third, the final classification map is produced by applying a supervised spectral classifier (i.e., random forest) on the fused features. In the experiments, the proposed method is applied to a three-sensor (RGB, multispectral LiDAR, and hyperspectral images) dataset captured over the area of the University of Houston, the USA, and a two-sensor (hyperspectral and LiDAR) dataset captured over the city of Trento, Italy. The land-cover maps generated using SubFus are evaluated based on classification accuracies. Experimental results obtained by SubFus confirm considerable improvements in terms of classification accuracies compared with the other methods used in the experiments. The proposed fusion approach obtains 85.32% and 99.25% in terms of overall classification accuracy on the Houston (the training portion of the dataset distributed for the data fusion contest of 2018) and trento datasets, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-32032
Publ.-Id: 32032


The Road to Exascale

Stephan, J.

Exascale is the next big step in the field of high-performance computing. However, the hardware configurations of supercomputers around the world are becoming increasingly heterogeneous. Programmers have to take into account varying processor architectures (x86, ARM, RISC-V, ...) as well as different accelerator types (multicore CPUs, GPUs, FPGAs, ...) and the accompanying tools. Our goal is a portable stack of C++ libraries and tools. Together they shall form an ecosystem which abstracts away the differences between hardware configurations without sacrificing performance.

Keywords: alpaka; C++; heterogeneous computing; heterogeneous programming; HPC; hardware abstraction

  • Open Access Logo Poster
    Polish delegation meeting, 29.09.2020, Görlitz, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-32031
Publ.-Id: 32031


Four-Frequency Solution in a Magnetohydrodynamic Couette Flow as a Consequence of Azimuthal Symmetry Breaking

Garcia, F.; Seilmayer, M.; Giesecke, A.; Stefani, F.

The occurrence of magnetohydrodynamic quasiperiodic flows with four fundamental frequencies in differentially rotating spherical geometry is understood in terms of a sequence of bifurcations breaking the azimuthal symmetry of the flow as the applied magnetic field strength is varied. These flows originate from unstable periodic and quasiperiodic states with broken equatorial symmetry, but having fourfold azimuthal symmetry. A posterior bifurcation gives rise to twofold symmetric quasiperiodic states, with three fundamental frequencies, and a further bifurcation to a four-frequency quasiperiodic state which has lost all the spatial symmetries. This bifurcation scenario may be favored when differential rotation is increased and periodic flows with m-fold azimuthal symmetry, m being a product of several prime numbers, emerge at sufficiently large magnetic field.

Keywords: Astrophysical fluid dynamics; Bifurcations; Chaos; Flow instability; Geophysical fluid dynamics; Magnetohydrodynamics

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Permalink: https://www.hzdr.de/publications/Publ-32030
Publ.-Id: 32030


Laser produced electromagnetic pulses: generation, detection and mitigation

Consoli, F.; Tikhonchuk, V. T.; Bardon, M.; Bradford, P.; Carrol, D. C.; Cikhardt, J.; Cipriani, M.; Clarke, R. J.; Cowan, T. E.; Danson, C. N.; de Angelis, R.; de Marco, M.; Dubois, J.-L.; Etchessahar, B.; Laso Garcia, A.; Hillier, D. I.; Weiman, J.; Kmetik, V.; Krasa, J.; Li, Y.; Lubrano, F.; McKenna, P.; Metzkes-Ng, J.; Poye, A.; Prencipe, I.; Raczka, P.; Smith, R. A.; Vrana, R.; Woolsey, N. C.; Zemaityte, E.; Zhang, Y.; Zhang, Z.; Zielbauer, B.; Neely, D.; Honsa, A.

This paper provides an up-to-date review of the problems related to the generation, detection and mitigation of strong electromagnetic pulses created in the interaction of high-power, high-energy laser pulses with different types of solid targets. It includes new experimental data obtained independently at several international laboratories. The mechanisms of electromagnetic field generation are analyzed and considered as a function of the intensity and the spectral range of emissions they produce. The major emphasis is put on the GHz frequency domain, which is the most damaging for electronics and may have important applications. The physics of electromagnetic emissions in other spectral domains, in particular THz and MHz, is also discussed. The theoretical models and numerical simulations are compared with the results of experimental measurements, with special attention to the methodology of measurements and complementary diagnostics. Understanding the underlying physical processes is the basis for developing techniques to mitigate the electromagnetic threat and to harness electromagnetic emissions, which may have promising applications.

Keywords: Electromagnetic Pulses; High-Power Lasers; Diagnostics; Mitigation Techniques

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Permalink: https://www.hzdr.de/publications/Publ-32029
Publ.-Id: 32029


Deep model simulation of polar vortices in gas giant atmospheres

Garcia, F.; Chambers, F. R. N.; Watts, A. L.

The Cassini and Juno probes have revealed large coherent cyclonic vortices in the polar regions of Saturn and Jupiter, a dramatic contrast from the east–west banded jet structure seen at lower latitudes. Debate has centred on whether the jets are shallow, or extend to greater depths in the planetary envelope. Recent experiments and observations have demonstrated the relevance of deep convection models to a successful explanation of jet structure, and cyclonic coherent vortices away from the polar regions have been simulated recently including an additional stratified shallow layer. Here we present new convective models able to produce long-lived polar vortices. Using simulation parameters relevant for giant planet atmospheres we find flow regimes of geostrophic turbulence (GT) in agreement with rotating convection theory. The formation of large-scale coherent structures occurs via 3D upscale energy transfers. Our simulations generate polar characteristics qualitatively similar to those seen by Juno and Cassini: They match the structure of cyclonic vortices seen on Jupiter; or can account for the existence of a strong polar vortex extending downwards to lower latitudes with a marked spiral morphology, and the hexagonal pattern seen on Saturn. Our findings indicate that these vortices can be generated deep in the planetary interior. A transition differentiating these two polar flows regimes is described, interpreted in terms of force balances and compared with shallow atmospheric models characterizing polar vortex dynamics in giant planets. In addition, heat transport properties are investigated, confirming recent scaling laws obtained with reduced models of GT.

Keywords: convection; turbulence; software: simulations; planets and satellites: gaseous planets

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Permalink: https://www.hzdr.de/publications/Publ-32028
Publ.-Id: 32028


Bremsstrahlung emission and plasma characterization driven by moderately relativistic laser-plasma interactions

Singh, S. K.; Armstrong, C.; Kang, N.; Ren, L.; Liu, H.; Hua, N.; Rusby, D. R.; Klimo, O.; Versaci, R.; Zhang, Y.; Sun, M.; Zhu, B.; Lei, A.; Ouyang, X.; Lancia, L.; Laso Garcia, A.; Wagner, A.; Cowan, T. E.; Schlegel, T.; Weber, S.; McKenna, P.; Neely, D.; Tikhonchuk, V. T.; Kumar, D.; Zhu, J.

Relativistic electrons generated by the interaction of petawatt-class short laser pulses with solid targets can be used to generate bright X-rays via bremsstrahlung. The efficiency of laser energy transfer into these electrons depends on multiple parameters including focused intensity and pre-plasma level. This paper describes the experimental results from the interaction of a high intensity petawatt-class glass laser with solid targets at a maximum intensity of 10^19 W/cm^2. In-situ measurements of specularly reflected light were used to provide an upper bound of laser absorption and to characterize focused laser intensity, the pre-plasma level and the generation mechanism of second harmonic light. The measured spectrum of electrons and bremsstrahlung radiation provide information about the efficiency of laser energy transfer.

Keywords: Plasma Physics; Bremsstrahlung; High intensity laser

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Permalink: https://www.hzdr.de/publications/Publ-32027
Publ.-Id: 32027


Biohydrometallurgy

Lederer, F.; Pollmann, K.

Biohydrometallurgy is one of many different processes for metal recovery. As a highly interdisciplinary field, biohydrometallurgy combines microorganisms and their metabolites (-bio) in a mainly aquatic environment (-hydro) and the treatment of metal containing materials or solutions (-metallurgy) for metal production and treatment. It is applied to many different metal-rich materials from primary mineral sources, secondary mining products and numerous manufactured resources (Watling, 2015). Biohydrometallurgy is using biological tools for the processing of primary ores for many years – especially in case of bioleaching. Besides that, special biological tools can enhance the metal recovery from manufactured resources such as technical waste products, processing wastes, industrial waste waters and other secondary sources (Pollmann et al. 2018). In nature multiple processes exist that influence biogeochemical cycles of elements. These microorganism driven processes contribute to bioaccumulation, bio weathering, biomineralization and precipitation or microbial reduction. Using these bio-inspired processes promotes biological recycling strategies as well as several clean industrial processes, bio-based materials and bioremediation. Modern bio-based approaches that are currently being developed for the recycling of value elements found in technical products contributing to a “green” circular economy. Main processes in biohydrometallurgy are bioleaching, biosorption, bioflotation and bioreduction.

Keywords: Biohydrometallurgy; Bioleaching; Biosorption; Bioflotation; Bioreduction; Bioaccumulation

  • Book chapter
    Maria E. Holuszko, Amit Kumar, Denise C.R. Espinosa: Electronic Waste: Recycling and Reprocessing for a Sustainable Future, Weinheim, Germany: Wiley-VCH Verlag GmbH, 2021, 978-3-527-34490-1, 189-202

Permalink: https://www.hzdr.de/publications/Publ-32026
Publ.-Id: 32026


Chaotic wave dynamics in weakly magnetized spherical Couette flows

Garcia Gonzalez, F.; Seilmayer, M.; Giesecke, A.; Stefani, F.

Direct numerical simulations of a liquid metal filling the gap between two concentric spheres are presented. The flow is governed by the interplay between the rotation of the inner sphere (measured by the Reynolds number Re) and a weak externally applied axial magnetic field (measured by the Hartmann number Ha). By varying the latter, a rich variety of flow features, both in terms of spatial symmetry and temporal dependence, is obtained. Flows with two or three independent frequencies describing their time evolution are found as a result of Hopf bifurcations. They are stable on a sufficiently large interval of Hartmann numbers where regions of multistability of two, three, and even four types of these different flows are detected. The temporal character of the solutions is analyzed by means of an accurate frequency analysis and Poincaré sections. An unstable branch of flows undergoing a period doubling cascade and frequency locking of three-frequency solutions is described as well.

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Permalink: https://www.hzdr.de/publications/Publ-32025
Publ.-Id: 32025


Printable anisotropic magnetoresistance sensors for highly compliant electronics

Oliveros Mata, E. S.; Canon Bermudez, G. S.; Ha, M.; Kosub, T.; Zabila, Y.; Faßbender, J.; Makarov, D.

Printed electronics are attractive due to their low-cost and large-area processing features, which have been successfully extended to magnetoresistive sensors and devices. Here, we introduce and characterize a new kind of magnetoresistive paste based on the anisotropic magnetoresistive (AMR) effect. The paste is a composite of 100-nm-thick permalloy/tantalum flakes embedded in an elastomer matrix, which promotes the formation of appropriately conductive percolation networks. Sensors printed with this paste showed stable magnetoresistive properties upon mechanical bending. The AMR value of this sensor is 0.34% in the field of 400 mT. Still, the response is stable and allows to resolve sub-mT field steps. When printed on ultra-thin 2.5-μm-thick Mylar foil, the sensor can be completely folded without losing magnetoresistive performance and mechanically withstand 20 μm bending radius. The developed compliant printed AMR sensor would be attractive to implement on curved and/or dynamic bendable surfaces for on-skin applications and interactive printed electronics.

Keywords: Flexible sensor; Anisotropic magnetoresistance; Printed electronics

Permalink: https://www.hzdr.de/publications/Publ-32024
Publ.-Id: 32024


Untersuchungen zur Optimierung der Selektivität bei der Extraktion von Indium durch gezielte Komplexbildung

Göthel, J.

Indium kann sekundärmetallurgisch aus der Prozessierung von Schlacken, Flugstäuben und metallischen Zwischenprodukten aus der Zinkdarstellung gewonnen werden. Eine weitere Möglichkeit der Indiumgewinnung stellt sich in der Aufbereitung von Rückständen des Bergbaus durch Biolaugungsprozesse dar. Höhere Konzentrationen an Eisen und Zink sind in den gewinnbaren Laugen im Vergleich zu sehr niedrigen Indiumkonzentrationen häufig präsent. Ein Trenn- und Aufbereitungsverfahren für die Verarbeitung von hydro-metallurgischen Prozesslösungen und die Gewinnung von Einsatzstoffen aus diesen wird durch Ionenaustauscherharze realisiert. Sowohl kationische als auch anionische feste Ionenaustauscherharze zeigen für Indium in sauren wässrigen Lösungen eine Affinität für die Indiumadsorption. Hinsichtlich der selektiven Adsorption von Indium gegenüber Eisen und Zink mittels festen Anionenaustauschern wurde der Einfluss der selektiven Komplexbildung von Indium durch die Zugabe von Iod in der Form von Kaliumiodid auf die Adsorption untersucht. Als Referenzsystem wurde die Indiumadsorption an festen Kationen-austauscherharzen gewählt. Die selektive Adsorption für Indium wurde aus einer vereinfachten Modelllösung der Biolaugungslösung des „ReMining“-Projektes hinsichtlich der Faktorgrößen des pH-Wertes, der Kaliumiodid- und Indiumadsorption im kleineren Maßstab im Becherglas untersucht. Die bestimmten Optima wurden auf die Prozessierung der realen Biolaugungslösung in Ionenaustauschersäulen angewandt. Indium kann in vergleichbaren quantitativen Mengen sowohl als anionischer Komplex ([InI4]-) von den getesteten Anionenaustauscherharzen A 111 und A 500 als auch von dem Kationenaustauscherharz MTS 9300 als Kation In3+ durch Adsorption aus der Modell- und Biolaugungslösung extrahiert werden. Beide Ionenaustauscher zeigen höchste Selektivitäten gegenüber Eisen, Arsen und Aluminium. Der Vergleich der Konzentrationsverhältnisse von Feed und dem Eluat zeigt, dass Eisen zu ~ 700 Mal mehr wie Indium (Fe/In = ~ 700) im Feed vorhanden ist und nach dem Ionenaustausch ~ 0,7 Mal so viel wie Indium (Fe/In = ~ 0,7) im Eluat verbleibt. Kupfer und Cadmium konnten von dem Anionenaustauscherharz A 111 nicht mit destilliertem Wasser und 0,1 M Schwefelsäure eluiert werden. In der Gesamtbetrachtung der selektiven Adsorption und Eluation von Indium aus der realen Biolaugungslösung ist das Kationenaustauscherharz MTS 9300 dem Anionenaustauscherharz A 111 vorzuziehen.

  • Diploma thesis
    TU Bergakademie Freiberg, 2020
    Mentor: Toni Helbig/Arite Werner

Permalink: https://www.hzdr.de/publications/Publ-32023
Publ.-Id: 32023


A bimodal soft electronic skin for tactile and touchless interaction in real time

Ge, J.; Wang, X.; Drack, M.; Volkov, O.; Liang, M.; Canon Bermudez, G. S.; Wang, C.; Zhou, S.; Faßbender, J.; Kaltenbrunner, M.; Makarov, D.

The transformative emergence of smart electronics, human-friendly robotics and supplemented or virtual reality will revolutionize the interplay with our surrounding. The complexity that is involved in the manipulation of objects in these emerging technologies is dramatically increased, which calls for electronic skins (e-skin) that can conduct tactile and touchless sensing events in a simultaneous and unambiguous way. Integrating multiple functions in a single sensing unit offers the most promising path towards simple, scalable and intuitive-to-use e-skin architectures. However, by now, this path has always been hindered by the confusing overlap of signals from different stimuli.
Here, we put forward the field of soft, flexible electronics by developing a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [1]. For the first time, the electric signals from tactile and touchless interactions are intrinsically separated into two different regions, allowing the m-MEMS, a single sensor unit, to unambiguously distinguish the two modes without knowing the signal history.
Owing to its intrinsic magnetic functionality, our complaint m-MEMS platform is able to discriminate magnetic vs. non-magnetic objects already upon touchless interaction. With this intrinsic selectivity, we address the long-standing problem in the field of touchless interaction – namely, the issue of interference with objects, which are irrelevant or even disturbing the interaction process. In addition, the interaction process is programmable. The sensitivity of the two interaction modes could be tuned by adjusting the magnetic field of the objects able to meet the requirements of different interaction tasks.
By using tactile and touchless sensing functions simultaneously, our m-MEMS e-skins enable complex interactions with a magnetically functionalized physical object that is supplemented with content data appearing in the virtual reality. We demonstrated data selection and manipulation with our m-MEMS e-skins leading to the realization of a multi-choice for augmented reality through three dimensional (3D) touch. Beyond the field of augmented reality, our m-MEMS will bring great benefits for healthcare, e.g. to ease surgery operations and manipulation of medical equipment, as well as for humanoid robots to overcome the challenging task of grasping.

[1] J. Ge, X. Wang, M. Drack, O. Volkov, M. Liang, G. S. Cañón Bermúdez, R. Illing, C. Wang, S. Zhou, J. Fassbender, M. Kaltenbrunner, and D. Makarov. A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Lecture (Conference) (Online presentation)
    2020 MRS Fall Meeting, 02.12.2020, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-32022
Publ.-Id: 32022


Flexible highly compliant magnetoelectronics

Canon Bermudez, G. S.; Ge, J.; Faßbender, J.; Kaltenbrunner, M.; Makarov, D.

Mechanical flexibility and even stretchability of functional elements is a key enabler of numerous applications including wearable electronics, healthcare and medical appliances. The magnetism community developed the family of high-performance shapeable magnetoelectronics [1], which contain flexible [2-4], printable [5-7], stretchable [8-11] and even mechanically imperceptible [12-16] magnetic field sensorics. The technology relies on a smart combination of thin inorganic functional elements prepared directly on flexible or elastomeric supports. The concept of shapeable magnetoelectronics is explored for various applications ranging from automotive [17] through consumer electronics and point of care [2,18] to virtual and augmented reality [14-16] applications.
Here, we will focus on the use of compliant magnetosensitive skins [14-16] for augmented reality systems. We demonstrate that e-skin compasses [14] allow humans to orient with respect to earth’s magnetic field ubiquitously. The biomagnetic orientation enables the realization of a touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins (Fig. 1).
This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [16] (Fig. 2). We demonstrate data selection and manipulation with our m-MEMS e-skins leading to the realization of a multi-choice menu for augmented reality through three dimensional (3D) touch. Beyond the field of augmented reality, our m-MEMS will bring great benefits for healthcare, e.g. to ease surgery operations and manipulation of medical equipment, as well as for humanoid robots to overcome the challenging task of grasping.
[1] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[2] G. Lin, D. Makarov et al., Lab Chip 14, 4050 (2014).
[3] N. Münzenrieder, D. Makarov et al., Adv. Electron. Mater. 2, 1600188 (2016).
[4] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1274 (2015).
[5] D. Makarov et al., ChemPhysChem (Review) 14, 1771 (2013).
[6] D. Karnaushenko, D. Makarov et al., Adv. Mater. 24, 4518 (2012).
[7] D. Karnaushenko, D. Makarov et al., Adv. Mater. 27, 880 (2015).
[8] M. Melzer, D. Makarov et al., J. Phys. D: Appl. Phys. (Review) 53, 083002 (2020).
[9] M. Melzer, D. Makarov et al., Nano Lett. 11, 2522 (2011).
[10] M. Melzer, D. Makarov et al., Adv. Mater. 24, 6468 (2012).
[11] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1333 (2015).
[12] M. Melzer, D. Makarov et al., Nat. Commun. 6, 6080 (2015).
[13] P. N. Granell, D. Makarov et al., npj Flexible Electronics 3, 3 (2019).
[14] G. S. Cañón Bermúdez, D. Makarov et al., Nature Electronics 1, 589 (2018).
[15] G. S. Cañón Bermúdez, D. Makarov et al., Science Advances 4, eaao2623 (2018).
[16] J. Ge, D. Makarov et al., Nature Communications 10, 4405 (2019).
[17] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1274 (2015).
[18] G. Lin, D. Makarov et al., Lab Chip (Review) 17, 1884 (2017).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Lecture (Conference) (Online presentation)
    65th Annual Conference on Magnetism and Magnetic Materials, 03.11.2020, Palm Beach, USA

Permalink: https://www.hzdr.de/publications/Publ-32021
Publ.-Id: 32021


Druckbare Hochleistungs-Magnetoelektronik

Makarov, D.

Gedruckte Elektronik wird das Gebiet der konventionellen Elektronik revolutionieren und eine kostengünstige, großflächige Produktion mit hohem Durchsatz ermöglichen. Durch Hinzufügen eines Magnetfeldsensors zur Familie der druckbaren Elektronik [1] wollen wir energieeffiziente kontaktlose Schalter für intelligente Verpackungen oder Postkarten sowie intelligente und schützende Kleidung (z. B. für Feuerwehrleute, Sportler) realisieren mit einem In- Stoff integrierte Navigations- und Positionsverfolgungsmodule. Für dieses Konzept wurden hochleistungsfähige druckbare Magnetfeldsensoren realisiert, die auf dem Riesenmagnetowiderstandseffekt (GMR) beruhen [2]. Diese Sensoren werden aus einer Paste gedruckt, die GMR-Flocken enthält, welche mittels Dünnschichttechnologien hergestellt wurden. Solche GMR-Sensoren können auch auf flexiblen Substraten siebgedruckt werden und bleiben in einem Temperaturbereich von -10°C bis +95°C [3] gemäß den Anforderungen an die Unterhaltungselektronik voll funktionsfähig.
In dieser Präsentation werden wir die aktuelle Technologie zur Realisierung von druckbaren Hochleistungs-Magnetfeldsensoren überprüfen. Wir werden zeigen, dass GMR-Sensoren auf ultradünne Polymerfolien mit einer Foliendicke von bis zu 6 µm gedruckt werden können. Die Verwendung eines geeigneten Polymerbindemittels für die GMR-Paste gewährleistet hervorragende Perkolationskontakte zwischen GMR-Mikroflocken und ermöglicht eine hohe Sensorempfindlichkeit von 3 T-1 bei einem niedrigen Magnetfeld von etwa 1 mT. Die Haftung zwischen dem gedruckten Sensor und der Polymerfolie ist ausreichend stark, um einer Biegung des Sensors auf einen Krümmungsradius von 16 µm standzuhalten, ohne die mechanische Integrität der Vorrichtung zu beeinträchtigen. Mit dieser Leistung können unsere gedruckten GMR-Sensoren für interaktive Elektronik auf der Haut verwendet werden, die wir mit einer berührungslosen Steuerung virtueller Objekte für die praktische Anwendung in tragbaren Geräten, künstlicher Prothetik, Robotik und im Internet der Dinge präsentieren.
[1] D. Makarov et al., ChemPhysChem (Review) 14, 1771 (2013).
[2] D. Karnaushenko, D. Makarov et al., Adv. Mater. 24, 4518 (2012).
[3] D. Karnaushenko, D. Makarov et al., Adv. Mater. 27, 880 (2015).

Keywords: flexible electronics; printed electronics; printed magnetic field sensors

  • Invited lecture (Conferences)
    8. Dresdner Werkstoffsymposium – Innovative Werkstoffe für neue Produkte, 02.-03.06.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-32020
Publ.-Id: 32020


Nanomagnetism of Magnetoelectric Granular Thin-Film Antiferromagnets

Makarov, D.

Thin film magnetoelectric antiferromagnets (AF) have potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. To explore their application potential, it is necessary to understand modifications of the magnetic properties of AF thin films with respect to their bulk counterparts. We will outline our developments of zero-offset anomalous Hall magnetometry [1] applied to study the physics of insulating magnetoelectric Cr2O3 antiferromagnets. The analysis of the transport data is backed up by the real space imaging of AF domain patterns using NV microscopy [2,3]. Considering grainy morphology of thin films, we address questions regarding the change of the intergranular exchange [3], criticality behavior and switching of the order parameter [1] and physics of the readout signal in α-Cr2O3 interfaced with Pt [4]. The possibility to read-out the antiferromagnetic order parameter all-electrically enabled a new recording concept of antiferromagnetic magnetoelectric random access memory (AF-MERAM) [2].
[1] T. Kosub et al., Phys. Rev. Lett. 115, 097201 (2015).
[2] T. Kosub et al., Nat. Commun. 8, 13985 (2017).
[3] P. Appel et al., Nano Lett. 19, 1682 (2019)
[4] R. Schlitz et al., Appl. Phys. Lett. 112, 132401 (2018).

Keywords: magnetoelectric antiferromagnets; thin films

  • Invited lecture (Conferences)
    15th International Conference on Modern Materials and Technologies: 9th Forum on New Materials, 24.-29.06.2022, Perugia, Italy

Permalink: https://www.hzdr.de/publications/Publ-32019
Publ.-Id: 32019


Advances in compliant magnetic field sensorics

Makarov, D.

The recent rapid advance and eagerness of portable consumer electronics stimulate the development of functional elements towards being lightweight, flexible, and wearable. Next generation flexible appliances aim to become fully autonomous and will require ultra-thin and flexible navigation modules, body tracking and relative position monitoring systems. Key building blocks of navigation and position tracking devices are magnetic field sensors.
Although there is a remarkable progress in the field of shapeable magnetoelectronics [1], until recently there was no technology available that can enable sensitivities to geomagnetic fields of 50 µT and, ultimately, magnetic fields of smaller than 1 µT in a mechanically compliant form factor. If available, these devices would contribute greatly to the realization of high-performance on-skin interactive electronics [2,3] and point of care applications [4,5].
Here, we will present technological platforms allowing to realize not only mechanically imperceptible electronic skins, which enable perception of the geomagnetic field (e-skin compasses) [6], but also enable sensitivities down to ultra-small fields of sub-50 nT [7]. We demonstrate that e-skin compasses allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactive devices for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins (fig. 1). This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [8]. Those devices are crucial for interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly compliant integrated feedback system as well as in medicine for physicians and surgeons.

[1] D. Makarov et al., Applied Physics Reviews 3 (2016), 011101.
[2] G. S. Canon Bermudez et al., Science Advances 4 (2018), eaao2623.
[3] M. Melzer et al., Nature Communications 6 (2015), 6080.
[4] G. Lin et al., Lab Chip 14 (2014), 4050.
[5] G. Lin et al., Lab Chip 17 (2017), 1884.
[6] G. S. Canon Bermudez et al., Nature Electronics 1 (2018), 589.
[7] P. N. Granell et al., npj Flexible Electronics 3 (2019), 3.
[8] J. Ge et al., Nature Communications (2019). doi:10.1038/s41467-019-12303-5

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences)
    IEEE Advances in Magnetics 2020, 14.06.2021, Moena, Italy

Permalink: https://www.hzdr.de/publications/Publ-32018
Publ.-Id: 32018


Compliant magnetic sensor technologies

Makarov, D.

We will review the recent progress in the field of shapeable magnetoelectronics [1] allowing to realize not only mechanically imperceptible electronic skins [2-4], which enable perception of the geomagnetic field (e-skin compasses) [5], but also enable sensitivities down to ultra-small fields of sub-50 nT [6]. We demonstrate that e-skin compasses allow humans to orient with respect to earth’s magnetic field ubiquitously. The biomagnetic orientation enables novel interactive devices for virtual and augmented reality applications, which is showcased by realizing touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins. This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [7]. Those devices are crucial for interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly compliant integrated feedback system as well as in medicine for physicians and surgeons
[1] D. Makarov et al., Applied Physics Reviews (Review) 3, 011101 (2016).
[2] M. Melzer, DM et al., J. Phys. D: Appl. Phys. (Review) 53, 083002 (2020).
[3] S. Canon, DM et al., Science Advances 4, eaao2623 (2018).
[4] M. Melzer, DM et al., Nature Communications 6, 6080 (2015).
[5] S. Canon, DM et al., Nature Electronics 1, 589 (2018).
[6] P.N. Granell, DM et al., npj Flexible Electronics 3, 3 (2019).
[7] J. Ge, DM et al., Nature Communications 10, 4405 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    8th International Symposium on Sensor Science, 21.05.2021, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-32017
Publ.-Id: 32017


Flexible Electronics: From Interactive Smart Skins to In vivo Applications

Makarov, D.

The portable consumer electronics necessitates functional elements to be lightweight, flexible, and wearable [1-4]. The unique possibility to adjust the shape of the devices offered by this alternative formulation of the electronics provides vast advantages over the conventional rigid devices particularly in medicine and consumer electronics. There is already a remarkable number of available flexible devices starting from interconnects, sensing elements towards complex platforms consisting of communication and diagnostic components.
We developed shapeable magnetoelectronics [5] – namely, flexible [6-8], printable [9,10], stretchable [11,12] and even imperceptible [13] magnetosensitive large area elements, which were completely missing in the family of flexible electronics. The unique mechanical properties open up new application potentials for smart skins, allowing to equip the recipient with a “sixth sense” providing new experiences in sensing and manipulating the objects of the surrounding us physical as well as digital world [7,13]. On the other hand, we realized self-assembled compact tubular microchannels based on strain engineering [14] with integrated passive sensory elements [15-17] and communication antenna devices [18] for on-chip and bio-medical applications, e.g. smart implants [19,20].
Combining these two research directions carried out at different length scales into a single truly interdisciplinary topic opens up the novel field of smart biomimetics [20]. In this respect, we demonstrated mechanically and electrically active compact biomimetic microelectronics, which can serve as a base for realization of novel regenerative neuronal cuff implants with unmatched functionalities. The biomimetic microelectronics can mechanically adapt to and impact the environment possessing the possibility to assess, adopt and communicate the environmental changes and even stimulate the environment electrically.
In my talk, these recent developments will be covered.

[1] M. G. Lagally, MRS Bull., 32, 57 (2007).
[2] J. A. Rogers et al., Nature, 477, 45 (2011).
[3] S. Bauer et al., Adv. Mater., 26, 149 (2014).
[4] M. Kaltenbrunner et al., Nature, 499, 458 (2013).
[5] D. Makarov et al., Appl. Phys. Rev., 3, 011101 (2016).
[6] G. Lin, D. Makarov et al., Lab Chip, 14, 4050 (2014).
[7] M. Melzer, D. Makarov et al., Adv. Mater., 27, 1274 (2015).
[8] N. Münzenrieder, D. Makarov et al., Adv. Electron. Mater., 2, 1600188 (2016).
[9] D. Karnaushenko, D. Makarov et al., Adv. Mater., 27, 880 (2015).
[10] D. Karnaushenko, D. Makarov et al., Adv. Mater., 24, 4518 (2012).
[11] M. Melzer, D. Makarov et al., Adv. Mater., 27, 1333 (2015).
[12] M. Melzer, D. Makarov et al., Nano Lett., 11, 2522 (2011).
[13] M. Melzer, D. Makarov et al., Nat. Commun., 6, 6080 (2015).
[14] O. G. Schmidt et al., Nature, 410, 168 (2001).
[15] I. Mönch, D. Makarov et al., ACS Nano, 5, 7436 (2011).
[16] C. Müller, D. Makarov et al., Appl. Phys. Lett., 100, 022409 (2012).
[17] E. J. Smith, D. Makarov et al., Lab Chip, 12, 1917 (2012).
[18] D. D. Karnaushenko, D. Makarov et al., NPG Asia Materials, 7, e188 (2015).
[19] D. Karnaushenko, D. Makarov et al., Adv. Mater., 27, 6582 (2015).
[20] D. Karnaushenko, D. Makarov et al., Adv. Mater., 27, 6797 (2015).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences)
    The International Conference on Metallurgical Coatings and Thin Films, 26.04.2021, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-32016
Publ.-Id: 32016


Curvilinear magnetism: geometrically curved ferro- and antiferromagnets

Makarov, D.

The main origin of the chiral symmetry breaking in magnetic materials is associated with the intrinsic Dzaloshinskii-Moriya interaction (DMI). At present, tailoring of DMI is done rather conventionally by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers. A viable alternative to the conventional material screening approach can be the exploration of the interplay between geometry and topology. The research field in magnetism, which is dealing with the study of the impact of geometrical curvature on magnetic responses of curved 1D wires and 2D shells is known as curvilinear magnetism [1]. The perspective of the development of curvilinear magnetism is outlined in the 2017 and 2020 Magnetism Roadmaps [2,3]. In this presentation, we will discuss on the recent achievements in the field and address the following topics:

A fully 3D approach to treat curvilinear effects in ferromagnetic nanowires and thin shells of arbitrary shape is established by Gaididei et al. back in 2014 [4] and was recently extended by Sheka et al. [5] to properly account for effects of non-locality due to the presence of long-range magnetostatic interaction. Volkov et al. has proven that the exchange-driven chiral effects in curvilinear ferromagnets are experimental observables [6] and can be used to realize nanostructures with tunable magnetochiral properties from standard magnetic materials.
In contrast to the intrinsic DMI, a concept of mesoscale Dzyaloshinskii-Moriya interaction was put forth, which is a result of the interplay between the intrinsic (spin-orbit-driven) and extrinsic (curvature-driven) DMI terms [7]. The mesoscale DMI governs the magnetochiral properties of any curvilinear ferromagnetic nanosystem and depends both on the material and geometrical parameters. Its strength and orientation can be tailored by properly choosing the geometry, which allows stabilizing distinct magnetic chiral textures including skyrmion and skyrmionium states as well as skyrmion lattices [8-10]. Interestingly, skyrmion states can be formed in a material even without an intrinsic DMI [8,10].
Sheka et al. [5] discovered a novel non-local chiral symmetry breaking effect, which does not exist in planar magnets: it is essentially non-local and manifests itself even in static spin textures living in curvilinear magnetic nanoshells. To identify this new interaction, a generalized micromagnetic theory of curvilinear ferromagnets was constructed accounting for local and nonlocal effects. The curvature leads to the emergence of the new magnetostatic charge, the geometrical charge, determined by the local characteristics of the surface. This newcomer is responsible for the appearance of novel fundamental chiral symmetry breaking effect.
The field of curvilinear magnetism was recently extended towards curvilinear antiferromagnets. Pylypovskyi et al. [11] demonstrated that intrinsically achiral one-dimensional curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable DMI, orientation of the Neel vector and the helimagnetic phase transition. This positions curvilinear antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spinorbitronics.

[1] Streubel et al., J. Phys. D: Appl. Phys. 49, 363001 (2016).
[2] Sander et al., J. Phys. D: Appl. Phys. 50, 363001 (2017).
[3] Vedmedenko et al., J. Phys. D: Appl. Phys. 53, 453001 (2020).
[4] Gaididei et al., PRL 112, 257203 (2014).
[5] Sheka et al., Communications Physics 3, 128 (2020).
[6] Volkov et al., PRL 123, 077201 (2019).
[7] Volkov et al., Scientific Reports 8, 866 (2018).
[8] Kravchuk et al., PRB 94, 144402 (2016).
[9] Kravchuk et al., PRL 120, 067201 (2018).
[10] Pylypovskyi et al., Phys. Rev. Appl. 10, 064057 (2018).
[11] Pylypovskyi et al., Nano Letters (2020). doi:10.1021/acs.nanolett.0c03246.

Keywords: curvilinear magnetism; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    MRS Spring Meeting, 21.04.2021, Seattle, USA

Permalink: https://www.hzdr.de/publications/Publ-32015
Publ.-Id: 32015


Mechanically shapeable magnetic field sensor technologies

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. For these applications, we developed a technology platform known as shapeable magnetoelectronics [2], which relies on a smart combination of ultrathin polymeric foils and metallic thin films featuring magnetoresistive and Hall effects. The mechanically compliant magnetic field sensors are designed and fabricated to address the specific needs of different applications including automotive (monitoring and control of electrical machines and drives) [3-5], biosensing technologies (flexible microfluidic devices) [6,7], consumer electronics (interactive printed electronics) [8,9], orientation in space [10] as well as virtual and augmented reality devices (motion tracking and touchless human-machine interaction) [10-13].
In this presentation, we will review the approaches to fabricate mechanically shapeable magnetic field sensors as well as their magnetoresistive and mechanical performance. On the application side, we will focus on the demonstration of the shapeable sensor devices for the emerging technological fields of smart skins, soft robotics and human-machine interfaces.

[1] R. Streubel, D. Makarov et al.: Magnetism in curved geometries. Journal of Physics D: Applied Physics (Topical Review) 49, 363001 (2016).
[2] D. Makarov et al.: Shapeable magnetoelectronics. Applied Physics Reviews 3, 011101 (2016).
[3] M. Melzer, D. Makarov et al.: Wearable magnetic field sensors for flexible electronics. Advanced Materials 27, 1274 (2015).
[4] D. Ernst, D. Makarov et al.: Packaging technologies for (ultra-)thin sensor applications in active magnetic bearings. IEEE Proceedings of the 37th International Spring Seminar on Electronics Technology (ISSE), pp. 125-129 (2014). doi:10.1109/ISSE.2014.6887577
[5] I.J. Mönch, D. Makarov et al.: Flexible Hall sensorics for flux based control of magnetic levitation. IEEE Trans. Magn. 51, 4004004 (2015).
[6] G. Lin, D. Makarov et al.: Magnetic sensing platform technologies for biomedical applications. Lab Chip 17, 1884 (2017).
[7] G. Lin, D. Makarov et al.: A highly flexible and compact magnetoresistive analytic device. Lab Chip 14, 4050 (2014).
[8] D. Makarov et al.: Printable magnetoelectronics. ChemPhysChem 14, 1771 (2013).
[9] D. Karnaushenko, D. Makarov et al.: High-performance magnetic sensorics for printable and flexible electronics. Advanced Materials 27, 880 (2015).
[10] G. S. Cañón Bermúdez, D. Makarov et al.: Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[11] G. S. Cañón Bermúdez, D. Makarov et al.: Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[12] J. Ge, D. Makarov et al.: A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[13] P. N. Granell, D. Makarov et al.: Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences)
    27. NDVaK - Sensorik auf polymeren Oberflächen, 17.03.2021, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-32014
Publ.-Id: 32014


Artificial magnetoception enabled by wearable magnetic field sensors

Makarov, D.

In this talk I will review our activities on the realization of magnetoceptive smart skins.

Keywords: flexible electronics; shapeable magnetoelectronics

  • Lecture (others) (Online presentation)
    Seminar at the Technical University of Chemnitz, 27.01.2021, Chemnitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-32013
Publ.-Id: 32013


Curvilinear magnetism: From curvature induced magnetochirality to shapeable magnetoelectronics

Makarov, D.

Non-collinear magnetic textures like spin spirals, chiral domain walls or skyrmions are typically stabilized by the intrinsic spin-orbit induced Dzyaloshinskii-Moriya interaction (DMI) [1]. Curvature effects emerged as a novel mean to design chiral magnetic responses relying on extrinsic parameters, i.e. geometrical curvature of thin films [2-4]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [5-7]. Vast majority of activities are dedicated to curved ferromagnets, where recent achievements include the development of the theory of curvilinear micromagnetism [3] and the first experimental confirmation of curvature-driven chiral effects stemming from the exchange interaction [4]. Only very recently, the focus was put also on curvilinear antiferromagnets. Pylypovskyi et al. [8] demonstrated that intrinsically achiral one-dimensional curvilinear antiferromagnets behave as a chiral helimagnet with geometrically tunable DMI and orientation of the Neel vector.
The application potential of 3D-shaped magnetic thin films is currently being explored as mechanically shapeable magnetic field sensors [9] for automotive applications, magnetoelectrics for memory devices, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics [10-12].
The fundamentals as well as application relevant aspects of curvilinear ferro- and antiferromagnets will be covered in this presentation.

References

[1] D. Sander, DM et al., J. Phys. D 50, 363001 (2017)
[2] R. Streubel, DM et al., J. Phys. D 49, 363001 (2016)
[3] D. Sheka, DM et al., Communications Physics 3, 128 (2020)
[4] O. M. Volkov, DM et al., Phys. Rev. Lett. 123, 077201 (2019)
[5] V. Kravchuk, DM et al., Phys. Rev. Lett. 120, 067201 (2018)
[6] O. Pylypovskyi, DM et al., Phys. Rev. Appl. 10, 064057 (2018)
[7] O. Pylypovskyi, DM et al., Phys. Rev. Lett. 114, 197204 (2015)
[8] O.Pylypovskyi, DM et al., Nano Lett. (2020) doi:10.1021/acs.nanolett.0c03246
[9] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)
[10] S. Canon Bermudez, DM et al., Science Advances 4, eaao2623 (2018)
[11] S. Canon Bermudez, DM et al., Nature Electronics 1, 589 (2018)
[12] J. Ge, DM et al., Nature Communications 10, 4405 (2019).

Keywords: curvilinear magnetism; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    736. WE-Heraeus-Seminar "Magnetism at the Nanoscale: Imaging ‐ Fabrication – Physics", 06.01.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-32012
Publ.-Id: 32012


Implantable Highly Compliant Devices for Heating of Internal Organs

Makarov, D.

Recent advances in the field of flexible electronics have opened the door for this technology to deeply impact the health care sector. The development of sensors and actuators which are lightweight and mechanically compliant enables them to be used for continuous health monitoring, on-site therapies or soft chirurgical ads. The key feature of these novel gadgets is their ability to provide targeted treatment and diagnosis without constraining the natural motion of the body or its internal organs.
Though many of these flexible diagnostic or therapeutic devices have been successfully demonstrated already, cancer treatment remains relatively unexplored in this field. In particular, hepatocellular carcinoma (HCC, liver cancer) is one of the leading causes of cancer related mortalities worldwide with a constantly growing incidence. Numerous efforts have been devoted to the development of targeted cancer treatments which selectively destroy cancer cells and spare the healthy tissue.
We propose and develop an implantable, multifunctional and highly compliant device for targeted thermal treatment of cancerous tissues [1]. The device is fabricated on a 6-µm-thick polymeric foil, which seamlessly conforms to the soft liver tissue and allows for precisely controlled joule heating without on-site rigid parts. Its high mechanical compliance provides stable readings even upon severe mechanical deformations, enabling temperature accuracies of 0.1°C at bending radii of 2.5 mm, characteristic for mouse liver tissues. This heating device can treat tissue over the whole range of temperatures leading to fever, hyperthermia and ablation, while using a driving current as low as 10 mA. We demonstrate the electro-thermal and mechanical characterization of the devices and study various heat impact scenarios on normal and cancerous tissue using autochthonous murine HCC models.
Due to their high mechanical compliance, stability and thermal treatment versatility, the here developed devices can become a complement or alternative solution to radio frequency ablation (RFA) techniques for cancer treatment.

[1] G. S. Cãnón Bermudez, A. Kruv, T. Voitsekhivska, I. Hochnadel, A. Lebanov, A. Potthoff, J. Fassbender, T. Yevsa, and D. Makarov, “Implantable Highly Compliant Devices for Heating of Internal Organs: Toward Cancer Treatment”. Adv. Eng. Mater. 21, 1900407 (2019).

Keywords: flexible electronics; cancer treatment

  • Invited lecture (Conferences) (Online presentation)
    International Conference on Advances in Biological Science and Technology (ICABST2020), 28.10.2020, Sanya, China

Permalink: https://www.hzdr.de/publications/Publ-32011
Publ.-Id: 32011


Flexible magnetic field sensors

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. We put forth the concept of shapeable magnetoelectronics [2] for various applications ranging from automotive [3-5] through consumer electronics to virtual and augmented reality [6-9] applications. These activities impact several emerging research fields of smart skins, soft robotics and human-machine interfaces. In this talk, recent fundamental and technological advancements in this research field will be reviewed.

[1] R. Streubel, D. Makarov et al., J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[3] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1274 (2015).
[4] I. J. Mönch, D. Makarov et al., IEEE Trans. Magn. 51, 4004004 (2015).
[5] D. Ernst, D. Makarov et al., IEEE Proceedings of the 37th International Spring Seminar on Electronics Technology (ISSE), pp. 125-129 (2014). doi:10.1109/ISSE.2014.6887577
[6] G. S. Cañón Bermúdez, D. Makarov et al., Science Advances 4, eaao2623 (2018).
[7] G. S. Cañón Bermúdez, D. Makarov et al., Nature Electronics 1, 589 (2018).
[8] P. N. Granell, D. Makarov et al., npj Flexible Electronics 3, 3 (2019).
[9] J. Ge, D. Makarov et al., Nature Communications 10, 4405 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    MSM2020: 15th International Conference Mechatronic Systems and Materials, 01.07.2020, Bialystok, Poland

Permalink: https://www.hzdr.de/publications/Publ-32010
Publ.-Id: 32010


Mechanically compliant magnetic field sensor technologies

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-7]. In this respect, we will present technological platforms allowing to realize not only mechanically imperceptible electronic skins, which enable perception of the geomagnetic field (e-skin compasses) [6], but also enable sensitivities down to ultra-small fields of sub-200 nT [8]. We demonstrate that e-skin compasses allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactive devices for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins. This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [7]. Those devices are crucial for interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly compliant integrated feedback system as well as in medicine for physicians and surgeons. In this talk, recent fundamental and technological advancements in this novel research field will be reviewed.

[1] R. Streubel, DM et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander, DM et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov, DM et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez, DM et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez, DM et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] J. Ge, DM et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[8] P. Granell, DM et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Lecture (others) (Online presentation)
    Seminar at the Karlsruhe Institute of Technology, 13.10.2020, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-32009
Publ.-Id: 32009


From curvilinear magnetism to shapeable magnetoelectronics

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-4]. On the other hand, we explore the application potential of 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [5] for automotive but also virtual and augmented reality appliances [6-8]. In this respect, we will present technological platforms allowing to realize not only mechanically imperceptible electronic skins, which enable perception of the geomagnetic field (e-skin compasses) [7], but also enable sensitivities down to ultra-small fields of sub-200 nT [9]. We demonstrate that e-skin compasses allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactive devices for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins. This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [8]. Those devices are crucial for interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly compliant integrated feedback system as well as in medicine for physicians and surgeons. In this talk, recent fundamental and technological advancements in this novel research field will be reviewed.

[1] R. Streubel, DM et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander, DM et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov, DM et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] V. P. Kravchuk, DM et al., Multiplet of Skyrmion states on a curvilinear defect: Reconfigurable Skyrmion lattices. Phys. Rev. Lett. 120, 067201 (2018).
[5] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[6] G. S. Cañón Bermúdez, DM et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[7] G. S. Cañón Bermúdez, DM et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[8] J. Ge, DM et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[9] P. Granell, DM et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).

Keywords: curvilinear magnetism; shapeable magnetoelectronics

  • Lecture (others)
    Seminar at the Johannes Kepler University Linz, 12.08.2020, Linz, Austria

Permalink: https://www.hzdr.de/publications/Publ-32008
Publ.-Id: 32008


Curvilinear Magnetism: Fundamentals and Applications

Makarov, D.

There is one aspect, which is in common to the majority of fundamentally appealing and technologically relevant novel magnetic materials, namely their non-collinear magnetic textures like spin spirals, chiral domain walls or skyrmions [1]. These textures are typically driven by the Dzyaloshinskii-Moriya interaction (DMI). Recently, curvature effects emerged as a novel mean to design chiral magnetic properties by relying on extrinsic parameters, e.g. geometry of thin films [2]. In particular, novel effects occur when the magnetization is modulated by curvature leading to new magnetization configurations and is implications on the spin dynamics due to topological constraints. Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films [3-5] and nanowires [6,7]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [8,9]. The application potential of 3D-shaped objects is currently being explored as mechanically reshapeable magnetic field sensorics [10] for flexible interactive electronics [11-13], magnetic field sensors [14-18], curvilinear magnetoelectrics for memory devices [19], spin-wave filters and high-speed racetrack memory devices [20]. To advance in this research field, novel theoretical methods and fabrication/characterization techniques [21-24]. The fundamentals as well as application relevant aspects of curvilinear nanomagnets will be covered in this presentation.

[1] D. Sander, DM et al., “The 2017 Magnetism Roadmap”, J. Phys. D 50, 363001 (2017).
[2] R. Streubel, DM et al., “Magnetism in curved geometries”, J. Phys. D 49, 363001 (2016).
[3] Y. Gaididei et al., “Curvature Effects in Thin Magnetic Shells”, Phys. Rev. Lett. 112, 257203 (2014).
[4] V. Kravchuk, DM et al., “Multiplet of Skyrmion States on a Curvilinear Defect: Reconfigurable Skyrmion Lattices”, Phys. Rev. Lett. 120, 067201 (2018).
[5] O. V. Pylypovskyi, DM et al., “Chiral Skyrmion and Skyrmionium States Engineered by the Gradient of Curvature”, Phys. Rev. Appl. 10, 064057 (2018).
[6] O. M. Volkov, DM et al., “Mesoscale Dzyaloshinskii-Moriya interaction: geometrical tailoring of the magnetochirality”, Scientific Reports 8, 866 (2018).
[7] O. M. Volkov, DM et al., “Experimental observation of exchange-driven chiral effects in curvilinear magnetism”, Phys. Rev. Lett. 123, 077201 (2019).
[8] O. V. Pylypovskyi, DM et al., “Coupling of Chiralities in Spin and Physical Spaces: The Möbius Ring as a Case Study”, Phys. Rev. Lett. 114, 197204 (2015).
[9] J. A. Otalora et al., “Curvature-Induced Asymmetric Spin-Wave Dispersion”, Phys. Rev. Lett. 117, 227203 (2016).
[10] D. Makarov et al., “Shapeable magnetoelectronics”, Appl. Phys. Rev. 3, 011101 (2016).
[11] S. Canon Bermudez, DM et al., “Magnetosensitive e-skins with directional perception for augmented reality”, Science Advances 4, eaao2623 (2018).
[12] S. Canon Bermudez, DM et al., “Electronic-skin compasses for geomagnetic field driven artificial magnetoreception and interactive electronics”, Nature Electronics 1, 589 (2018).
[13] J. Ge, DM et al., “A bimodal soft electronic skin for tactile and touchless interaction in real time”, Nature Comm. 10, 4405 (2019).
[14] D. Karnaushenko, DM et al., “Self-assemled on-chip integrated giant magneto-impedance sensorics”, Adv. Mater. 27, 6582 (2015).
[15] G. Lin, DM et al., “A highly flexible and compact magnetoresistive analytic device”, Lab Chip 14, 4050 (2014).
[16] N. Münzenrieder, DM et al., “Entirely flexible on-site conditioned magnetic sensorics”, Adv. Electron. Mater. 2, 1600188 (2016).
[17] C. Becker et al., “Self-assembly of highly sensitive 3D magnetic field vector angular encoders”, Science Advances 5, eaay7459 (2019).
[18] M. Kondo et al., “Imperceptible magnetic sensor matrix system integrated with organic driver and amplifier circuits”, Science Advances 6, eaay6094 (2020)
[19] O. M. Volkov, DM et al., “Concept of artificial magnetoelectric materials via geometrically controlling curvilinear helimagnets”, J. Phys. D: Appl. Phys. 52, 345001 (2019).
[20] M. Yan et al., “Beating the Walker Limit with Massless Domain Walls in Cylindrical Nanowires”, Phys. Rev. Lett. 104, 057201 (2010).
[21] R. Streubel, DM et al., “Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies”, Nature Comm. 6, 7612 (2015).
[22] T. Kosub, DM et al., “Purely antiferromagnetic magnetoelectric random access memory”, Nature Comm. 8, 13985 (2017).
[23] M. Huth et al., “Focused electron beam induced deposition meets materials science”, Microelectron. Engineering 185-186, 9 (2018).
[24] M. Nord, DM et al., “Strain Anisotropy and Magnetic Domains in Embedded Nanomagnets”, Small 15, 1904738 (2019).

Keywords: curvilinear magnetism; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    The 2020 Magnetism and Magnetic Materials Conference, 04.11.2020, Palm Beach, USA

Permalink: https://www.hzdr.de/publications/Publ-32007
Publ.-Id: 32007


Overview of recent advances in flexible highly compliant magnetoelectronics

Makarov, D.

Recent rapid advances and eagerness of portable consumer electronics stimulate the development of functional elements towards being lightweight, flexible, and wearable. Next generation flexible appliances aim to become fully autonomous and will require ultra-thin and flexible navigation modules, body tracking and relative position monitoring systems. Key building blocks of navigation and position tracking devices are magnetic field sensors. In this presentation, recent developments in the emerging field of flexible magnetic field sensorics and its applications in printed electronics, eMobility, virtual and augmented reality settings will be reviewed.

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    2020 IEEE Electron Devices Technology and Manufacturing Conference (EDTM), 06.04.2020, Penang, Malaysia

Permalink: https://www.hzdr.de/publications/Publ-32006
Publ.-Id: 32006


Electronic materials with nanoscale curved geometries

Gentile, P.; Cuoco, M.; Ying, Z.; Volkov, O.; Vera-Marun, I. J.; Makarov, D.; Ortix, C.

As the dimensions of a material shrink from an extended bulk solid to a nanoscale structure, size and quantum confinement effects become dominant, altering the properties of the material. Materials with nanoscale curved geometries, such as rolled-up nanomembranes and zigzag-shaped nanowires, have recently been found to exhibit a number of intriguing electronic and magnetic properties due to shape-driven modifications of charge motion or confinement effects. Local strain generated by curvature can also lead to changes in material properties due to electromechanical coupling. Here we review the development of electronic materials with nanoscale curved geometries. We examine the origin of shape-, confinement- and strain-induced effects and explore how to exploit these in electronic, spintronic and superconducting devices. We also consider the methods required to synthesize and characterize curvilinear nanostructures, and highlight key areas for the future development of curved electronics.

Keywords: curvature effects; curvilinear magnetism; shapeable magnetoelectronics

Permalink: https://www.hzdr.de/publications/Publ-32005
Publ.-Id: 32005


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