Dr. Jürgen Lindner

Tel.: +49 351 260 3221

Recent publications of the FWIN (magnetism) division

complete FWIN publication list

HZDR publication database


Determining the preferred directions of magnetisation in cubic crystals using symmetric polynomial inequalities

F. Samad, O. Hellwig

For a magnetic material, the easy and hard magnetic axes describe the directions of favourable respectively unfavourable alignment of the magnetisation. In this article, we describe how to determine these axes for cubic magnetic crystals. Usually it is assumed without further reasoning that they coincide with some principal symmetry directions of the crystal [Bozorth, Phys. Rev. 50, 1076–1081 (1936)], which is however invalid in general. In contrast, we present a full and elementary analysis using symmetric polynomial inequalities, which are well suited to the symmetry of the problem.

Keywords: Anisotropy; cubic magnetic anisotropy; symmetric polynomial inequalities; symmetry; cubic crystal


Chirality coupling in topological magnetic textures with multiple magnetochiral parameters

O. Volkov, D. Wolf, O. Pylypovskyi, A. Kakay, D. D. Sheka, B. Büchner, J. Faßbender, A. Lubk, D. Makarov

Chiral effects originate from the lack of inversion symmetry within the lattice unit cell or sample’s shape. Being mapped onto magnetic ordering, chirality enables topologically non-trivial textures with a given handedness. Here, we demonstrate the existence of a static 3D texture characterized by two magnetochiral parameters being magnetic helicity of the vortex and geometrical chirality of the core string itself in geometrically curved asymmetric permalloy cap with a size of 80 nm and a vortex ground state. We experimentally validate the nonlocal chiral symmetry breaking effect in this object, which leads to the geometric deformation of the vortex string into a helix with curvature 3 μm−1 and torsion 11 μm−1. The geometric chirality of the vortex string is determined by the magnetic helicity of the vortex texture, constituting coupling of two chiral parameters within the same texture. Beyond the vortex state, we anticipate that complex curvilinear objects hosting 3D magnetic textures like curved skyrmion tubes and hopfions can be characterized by multiple coupled magnetochiral parameters, that influence their statics and field- or current-driven dynamics for spin-orbitronics and magnonics.

Keywords: Non-local chiral symmetry breaking; Magnetic vortex

Modification of three-magnon splitting in a flexed magnetic vortex

L. Körber, C. Heins, I. Soldatov, R. Schäfer, A. Kakay, H. Schultheiß, K. Schultheiß

We present an experimental and numerical study of three-magnon splitting in a micrometer-sized magnetic disk with the vortex state strongly deformed by static in-plane magnetic fields. Excited with a large enough power at frequency fRF, the primary radial magnon modes of a cylindrical magnetic vortex can decay into secondary azimuthal modes via spontaneous three-magnon splitting. This nonlinear process exhibits selection rules leading to well-defined and distinct frequencies fRF/2±Δf of the secondary modes. Here, we demonstrate that three-magnon splitting in vortices can be significantly modified by deforming the magnetic vortex with in-plane magnetic fields, leading to a much richer three-magnon response. We find that, with increasing field, an additional class of secondary modes is excited which are localized to the highly-flexed regions adjacent to the displaced vortex core. While these modes satisfy the same selection rules of three-magnon splitting, they exhibit a much lower three-magnon threshold power compared to regular secondary modes of a centered vortex. The applied static magnetic fields are small (≃ 10 mT), providing an effective parameter to control the nonlinear spectral response of confined vortices. Our work expands the understanding of nonlinear magnon dynamics in vortices and advertises these for potential neuromorphic applications based on magnons.

Keywords: spin wave; magnon; vortex; BLS; micromagnetic modeling; Kerr microscopy; three-magnon splitting; reservoir computing

Verknüpfte Publikationen

  • Open Access Logo Applied Physics Letters 122(2023), 092401
    DOI: 10.1063/5.0135573
    arXiv: arXiv:2211.08226


Coupling of terahertz light with nanometre-wavelength magnon modes via spin–orbit torque

R. Salikhov, I. Ilyakov, L. Körber, A. Kakay, R. A. Gallardo, O. Ponomaryov, J.-C. Deinert, T. de Oliveira, K. Lenz, J. Faßbender, S. Bonetti, O. Hellwig, J. Lindner, S. Kovalev

Spin-based technologies can operate at terahertz frequencies but require manipulation techniques that work at ultrafast timescales to become practical. For instance, devices based on spin waves, also known as magnons, require efficient generation of high-energy exchange spin waves at nanometre wavelengths. To achieve this, a substantial coupling is needed between the magnon modes and an electro-magnetic stimulus such as a coherent terahertz field pulse. However, it has been difficult to excite non-uniform spin waves efficiently using terahertz light because of the large momentum mismatch between the submillimetre-wave radiation and the nanometre-sized spin waves. Here we improve the light–matter interaction by engineering thin films to exploit relativistic spin–orbit torques that are confined to the interfaces of heavy metal/ferromagnet heterostructures. We are able to excite spin-wave modes with frequencies of up to 0.6 THz and wavelengths as short as 6 nm using broadband terahertz radiation. Numerical simulations demonstrate that the coupling of terahertz light to exchange-dominated magnons originates solely from interfacial spin–orbit torques. Our results are of general applicability to other magnetic multilayered structures, and offer the prospect of nanoscale control of high-frequency signals.

Keywords: Magnonics; Spintronics; Terahertz; Magnetism

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Tailoring crosstalk between localized 1D spin-wave nanochannels using focused ion beams

V. Iurchuk, J. Pablo-Navarro, T. Hula, R. Narkovic, G. Hlawacek, L. Körber, A. Kakay, H. Schultheiß, J. Faßbender, K. Lenz, J. Lindner

1D spin-wave conduits are envisioned as nanoscale components of magnonics-based logic and computing schemes for future generation electronics. A-la-carte methods of versatile control of the local magnetization dynamics in such nanochannels are highly desired for efficient steering of the spin waves in magnonic devices. Here, we present a study of localized dynamical modes in 1-$\mu$m-wide Permalloy conduits probed by microresonator ferromagnetic resonance technique. We clearly observe the lowest-energy edge mode in the microstrip after its edges were finely trimmed by means of focused Ne+ ion irradiation. Furthermore, after milling the microstrip along its long axis by focused ion beams, creating consecutively ~50 and ~100 nm gaps, additional resonances emerge and are attributed to modes localized at the inner edges of the separated strips. To visualize the mode distribution, spatially resolved Brillouin light scattering microscopy was used showing an excellent agreement with the ferromagnetic resonance data and confirming the mode localization at the outer/inner edges of the strips depending on the magnitude of the applied magnetic field. Micromagnetic simulations confirm that the lowest-energy modes are localized within $\sim$15-nm-wide regions at the edges of the strips and their frequencies can be tuned in a wide range (up to 5 GHz) by changing the magnetostatic coupling (i.e. spatial separation) between the microstrips.

Keywords: Ferromagnetic resonance; Helium-ion microscope; Brillouin light scattering; Micromagnetic modelling; Magnetostatic coupling; Edge modes

Verknüpfte Publikationen

Spin wave non-reciprocity at the spin-flop transition region in synthetic antiferromagnets

O. Gladii, R. Salikhov, O. Hellwig, H. Schultheiß, J. Lindner, R. Gallardo

We investigate the frequency non-reciprocity in CoFeB/Ru/CoFeB synthetic antiferromagnets near the spin-flop transition region, where the magnetic moments in the two ferromagnetic layers are non-collinear. Using conventional Brillouin light scattering, we perform systematic measurements of the frequency non-reciprocity as a function of an external magnetic field. For the antiparallel alignment of the magnetic moments in the two layers, we observe a significant frequency non-reciprocity of up to a few GHz, which vanishes when the relative magnetization orientation switches into the parallel configuration at saturation. A non-monotonous dependence of the frequency non-reciprocity is found in the region where the system transitions from the antiparallel to the parallel orientation, with a maximum frequency shift around the spin-flop critical point. This non-trivial dependence of the non-reciprocity is attributed to the non-monotonous dependence of the dynamic dipolar interaction, which is the main factor that causes asymmetry in the dispersion relation. Furthermore, we found that the sign of the frequency shift changes even without switching the polarity of the bias field. These results show that one can precisely control the non-reciprocal propagation of spin waves via field-driven magnetization reorientation.

Keywords: Spin waves; Magnetization switching; Magnetization dynamics; Dipolar interaction; Magnetic multilayers; Synthetic antiferromagnets


Effects of the rf current and bias field direction on the transition from linear to non-linear gyrotropic dynamics in magnetic vortex structures

L. Ramasubramanian, V. Iurchuk, S. Sorokin, O. Hellwig, A. M. Deac

We present a frequency-domain study of the dynamic behavior of a magnetic vortex core within a single Permalloy disk by means of electrical detection and micromagnetic simulations. When exciting the vortex core dynamics in a nonlinear regime, the lineshape of the rectified dc signal reveals a resonance peak splitting which depends on the excitation amplitude. Using micromagnetic simulations, we show that at high excitation power the peak splitting originates from the nanosecond time scale quasiperiodic switching of the vortex core polarity. Using lock-in detection, the rectified voltage is integrated over a ms time scale, so that the net signal detected between the two resonant peaks for a given range of parameters cancels out. The results are in agreement with the reported effects of the in-plane static field magnitude on the gyration dynamics, and complement them by detailed analysis of the effects of the rf current amplitude and the azimuthal angle of the in-plane bias magnetic field. Systematic characterization shows that a transition from linear to nonlinear dynamical regime can be controlled by rf current as well as by varying the magnitude and the direction of the bias magnetic field.

Keywords: Spintronics; Magnetization dynamics; Magnetic vortex; Non-linear dynamics; Spin rectification effect; ED-FMR


Antiskyrmions and their electrical footprint in crystalline mesoscale structures of Mn1.4PtSn

M. Winter, F. J. Trindade Goncalves, I. Soldatov, Y. He, B. E. Zuniga Cespedes, P. Milde, K. Lenz, S. Hamann, M. Uhlarz, P. Vir, M. König, P. J. W. Moll, R. Schlitz, S. T. B. Goennenwein, L. M. Eng, R. Schäfer, J. Wosnitza, C. Felser, J. Gayles, T. Helm

Skyrmionic materials hold the potential for future information technologies, such as racetrack memories. Key to that advancement are systems that exhibit high tunability and scalability, with stored information being easy to read and write by means of all-electrical techniques. Topological magnetic excitations such as skyrmions and antiskyrmions, give rise to a characteristic topological Hall effect. However, the electrical detection of antiskyrmions, in both thin films and bulk samples has been challenging to date. Here, we apply magneto-optical microscopy combined with electrical transport to explore the antiskyrmion phase as it emerges in crystalline mesoscale structures of the Heusler magnet Mn1.4PtSn. We reveal the Hall signature of antiskyrmions in line with our theoretical model, comprising anomalous and topological components. We examine its dependence on the vertical device thickness, field orientation, and temperature. Our atomistic simulations and experimental anisotropy studies demonstrate the link between antiskyrmions and a complex magnetism that consists of competing ferromagnetic, antiferromagnetic, and chiral exchange interactions, not captured by micromagnetic simulations.

Verknüpfte Publikationen


Finite-element dynamic-matrix approach for propagating spin waves: Extension to mono- and multilayers of arbitrary spacing and thickness

L. Körber, A. Hempel, A. Otto, R. A. Gallardo, Y. Henry, J. Lindner, A. Kakay

In our recent work [L. Körber, AIP Advances 11, 095006 (2021)], we presented an efficient numerical method to compute dispersions and mode profiles of spin waves in waveguides with translationally invariant equilibrium magnetization. A finite-element method (FEM) allowed to model two-dimensional waveguide cross sections of arbitrary shape but only finite size. Here, we extend our FEM propagating-wave dynamic-matrix approach from finite waveguides to the important cases of infinitely-extended mono- and multilayers of arbitrary spacing and thickness. To obtain the mode profiles and frequencies, the linearized equation of motion of magnetization is solved as an eigenvalue problem on a one-dimensional line-trace mesh, defined along the normal direction of the layers. Being an important contribution in multilayer systems, we introduce interlayer exchange into our FEM approach. With the calculation of dipolar fields being the main focus, we also extend the previously presented plane-wave Fredkin-Koehler method to calculate the dipolar potential of spin waves in infinite layers. The major benefit of this method is that it avoids the discretization of any non-magnetic material like non-magnetic spacers in multilayers. Therefore, the computational effort becomes independent on the spacer thicknesses. Furthermore, it keeps the resulting eigenvalue problem sparse, which therefore, inherits a comparably low arithmetic complexity. As a validation of our method (implemented into the open-source finite-element micromagnetic package \textsc{TetraX}), we present results for various systems and compare them with theoretical predictions and with established finite-difference methods. We believe this method offers an efficient and versatile tool to calculate spin-wave dispersions in layered magnetic systems.

Verknüpfte Publikationen

Stimulated Resonant Inelastic X-Ray Scattering in a Solid

D. J. Higley, Z. Chen, M. Beye, M. Hantschmann, A. H. Reid, V. Mehta, O. Hellwig, G. L. Dakovski, A. Mitra, R. Y. Engel, T. Maxwell, Y. Ding, S. Bonetti, M. Bucher, S. Carron, T. Chase, E. Jal, R. Kukreja, T. Liu, A. Föhlisch, H. A. Dürr, W. F. Schlotter, J. Stöhr

When materials are exposed to X-ray pulses with sufficiently high intensity, various nonlinear
effects can occur. The most fundamental one consists of stimulated electronic decays after
resonant absorption of X-rays. Such stimulated decays enhance the number of emitted
photons and the emission direction is confined to that of the stimulating incident photons
which clone themselves in the process. Here we report the observation of stimulated reso-
nant elastic (REXS) and inelastic (RIXS) X-ray scattering near the cobalt L3 edge in solid Co/
Pd multilayer samples. We observe an enhancement of order 106 of the stimulated over the
conventional spontaneous RIXS signal into the small acceptance angle of the RIXS spectro-
meter. We also find that in solids both stimulated REXS and RIXS spectra contain con-
tributions from inelastic electron scattering processes, even for ultrashort 5 fs pulses.
Our results reveal the potential and caveats of the development of stimulated RIXS in
condensed matter.

Cooperative Effect of Electron Spin Polarization in Chiral Molecules Studied with Non-Spin-Polarized Scanning Tunneling Microscopy

T. Ngoc Ha Nguyen, L. Rasabathina, O. Hellwig, A. Sharma, G. Salvan, S. Yochelis, Y. Paltiel, L. T. Baczewski, C. Tegenkamp

Polyalanine molecules (PA) with an α-helix conformation have
recently attracted a great deal of interest, as the propagation of electrons through the
chiral backbone structure comes along with spin polarization of the transmitted
electrons. By means of scanning tunneling microscopy and spectroscopy under
ambient conditions, PA molecules adsorbed on surfaces of epitaxial magnetic Al2O3/
Pt/Au/Co/Au nanostructures with perpendicular anisotropy were studied. Thereby,
a correlation between the PA molecules ordering at the surface with the electron
tunneling across this hybrid system as a function of the substrate magnetization
orientation as well as the coverage density and helicity of the PA molecules was
observed. The highest spin polarization values, P, were found for well-ordered self-
assembled monolayers and with a defined chemical coupling of the molecules to the
magnetic substrate surface, showing that the current-induced spin selectivity is a
cooperative effect. Thereby, P deduced from the electron transmission along
unoccupied molecular orbitals of the chiral molecules is larger as compared to values
derived from the occupied molecular orbitals. Apparently, the larger orbital overlap results in a higher electron mobility, yielding a
higher P value. By switching the magnetization direction of the Co layer, it was demonstrated that the non-spin-polarized STM can
be used to study chiral molecules with a submolecular resolution, to detect properties of buried magnetic layers and to detect the
spin polarization of the molecules from the change in the magnetoresistance of such hybrid structures.

Role of vibrational properties and electron-phonon coupling on thermal transport across metal-dielectric interfaces with ultrathin metallic interlayers

S. Mary Oommen, L. Fallarino, J. Heinze, O. Hellwig, S. Pisana

We systematically analyze the influence of 5 nm thick metal interlayers inserted at the interface
of several sets of different metal-dielectric systems to determine the parameters that most
influence interface transport. Our results show that despite the similar Debye temperatures of
Al2O3 and AlN substrates, the thermal boundary conductance measured for the Au/Al2O3
system with Ni and Cr interlayers is ∼2× and >3× higher than the corresponding Au/AlN
system, respectively. We also show that for crystalline SiO2 (quartz) and Al2O3 substrates
having highly dissimilar Debye temperature, the measured thermal boundary conductance
between Al/Al2O3 and Al/SiO2 are similar in the presence of Ni and Cr interlayers. We suggest
that comparing the maximum phonon frequency of the acoustic branches is a better parameter
than the Debye temperature to predict the change in the thermal boundary conductance. We
show that the electron–phonon coupling of the metallic interlayers also alters the heat transport
pathways in a metal-dielectric system in a nontrivial way. Typically, interlayers with large
electron–phonon coupling strength can increase the thermal boundary conductance by dragging
electrons and phonons into equilibrium quickly. However, our results show that a Ta interlayer,
having a high electron–phonon coupling, shows a low thermal boundary conductance due to the
poor phonon frequency overlap with the top Al layer. Our experimental work can be interpreted
in the context of diffuse mismatch theory and can guide the selection of materials for thermal
interface engineering.

Keywords: hermal boundary conductance; metal-dielectric interfaces; Debye temperature; phonon frequencies; time-domain thermoreflectance

Tailoring exchange-dominated synthetic layered antiferromagnets: From collective reversal to exchange bias

B. Benny, O. Hellwig

Not only since the progressive reduction of structure sizes in modern micro- and nanotechnology, surface and interface effects have played an ever-increasing role and nowadays often dominate the behavior of entire systems. Therefore, understanding the nature of surface and interface effects and being able to fully control them is of fundamental importance, in particular in modern thin-film technology. In this study, it is revealed how Co/Pt multi-layer-based synthetic antiferromagnets (SAFs) with perpendicular magnetic anisotropy in the regime of dominating antiferromagnetic interlayer exchange can be employed to control the collective magnetic reversal via systemati-cally altering surface and interface effects. The specifically designed samples and experiments highlight the superior tunability of synthetic systems as compared to their intrinsic stoichiometric counterparts, where the antiferro-magnetism is directly tied to the indivisible discrete atomic nature and crystal structure of the materials. Thus, it is demonstrated that in SAFs, it becomes possible to energetically heal the broken magnetic symmetry at the surface, thereby enabling either on demand suppression or controlled enhancement of respective surface and interface effects, as demonstrated here in this study for the surface spin-flop and the exchange bias effect.


Application of a Microfabricated Microwave Resonator in a Co-Pd–Based Magnetic Hydrogen-Gas Sensor

T. A. Schefer, R. Narkovic, K. Lenz, F. Ganss, M. P. Roberts, O. Hellwig, M. Martyniuk, J. Lindner, M. Kostylev

We investigate the ferromagnetic resonance (FMR) response of microfabricated microwave resonators loaded with small Co16Pd84 alloy rectangles. A major increase in the FMR signal-to-noise ratio is achieved by employing the microwave-resonator structure. A FMR peak shift similar to that of Co16Pd84 continuous films is measured in the presence of hydrogen gas in the sample environment. We show that the very high sensitivity of the FMR signal of the Co16Pd84 alloy rectangle to hydrogen exposure can be used to measure relatively small hydrogen-concentration steps near 100% H2. Additionally, we also demonstrate that this structure can measure hydrogen over a concentration range from 3% to 100% H2 in N2. In time-dependent FMR measurements, we discover a temperature dependence of the FMR signal, which we relate to intrinsic temperature-dependent changes in saturation magnetization and the magnetic anisotropy of the Co-Pd alloy.

Keywords: hydrogen sensors; ferromagnetic resonance; CoPd alloys; Nanostructures; gas sensors


  • Zweitveröffentlichung erwartet ab 04.08.2023

Control and tunability of magnetic bubble states in multilayers with strong perpendicular magnetic anisotropy at ambient conditions

R. Salikhov, F. Samad, S. Sai Phani Kanth Arekapudi, R. Ehrler, J. Lindner, N. S. Kiselev, O. Hellwig

The reversal of magnetic bubble helicity through topologically trivial transient states provides an additional
degree of freedom that promises the development of multidimensional magnetic memories. A key requirement
for this concept is the stabilization of bubble states at ambient conditions on application-compatible substrates.
In the present work, we demonstrate a stabilization routine for remanent bubble states in high perpendicular
magnetic anisotropy [Co(0.44 nm)/Pt(0.7 nm)]X , X = 48, 100, and 150 multilayers on Si/SiO2 substrates by
exploring the effect of external magnetic fields (Hm) of different strength and angles (θ) with respect to the
film surface normal. By systematic variation of these two parameters, we demonstrate that remanent bubble
density and mean bubble diameter can be carefully tuned and optimized for each sample. Our protocol based on
magnetometry only reveals the densest remanent bubble states at Hm = 0.87Hs (Hs is the magnetic saturation
field) and θ = 60◦–75◦ for all X with a maximum of 3700 domains/100 μm2 for the X = 48 sample. The
experimental observations are supported by micromagnetic simulations, taking into account the nanoscale lateral
grain structure of multilayers synthesized by magnetron sputter deposition, and thus helping to understand the
different densities of the bubble states found in these systems.


Spin-wave channeling in magnetization-graded nanostrips

R. A. Gallardo, P. Alvarado-Seguel, F. Brevis, A. Roldán-Molina, K. Lenz, J. Lindner, P. Landeros

Magnetization-graded ferromagnetic nanostrips are proposed as potential prospects to channel spin waves. Here, a controlled reduction of the saturation magnetization enables the localization of the propagating magnetic excitations in the same way that light is controlled in an optical fiber with a varying refraction index. The approach is based on the dynamic matrix method, where the magnetic nanostrip is divided into small sub-strips. The dipolar and exchange interaction between sub-strips is accounted to reproduce the spin-wave dynamics of the magnonic fiber. The transition from one strip to an infinite thin film is presented for the Damon-Eshbach geometry, where the nature of the spin-wave modes is discussed. An in-depth analysis of the spin-wave transport as a function of the saturation magnetization profile is provided. It is predicted that it is feasible to induce a remarkable channeling of the spin waves along the zones with a reduced saturation magnetization, even when such a reduction is tiny. The results are compared with micromagnetic simulations, where a good agreement is observed between both methods. The findings have relevance for envisioned future spin-wave-based magnonic devices operating at the nanometer scale.

Keywords: spin waves; ferromagnetic resonance; magnetization dynamics; magnonics; magnetic gradients; theory

Curvilinear spin-wave dynamics beyond the thin-shell approximation: Magnetic nanotubes as a case study

L. Körber, R. Verba, J. A. Otálora, V. Kravchuk, J. Lindner, J. Faßbender, A. Kakay

Surface curvature of magnetic systems can lead to many static and dynamic effects which are not present in flat systems of the same material. These emergent magnetochiral effects can lead to frequency nonreciprocity of spin waves, which has been shown to be a bulk effect of dipolar origin and is related to a curvature-induced symmetry breaking in the magnetic volume charges. So far, such effects have been investigated theoretically mostly for thin shells, where the spatial profiles of the spin waves can be assumed to be homogeneous along the thickness. Here, using a finite-element dynamic-matrix approach, we investigate the transition of the spin-wave spectrum from thin to thick curvilinear shells, at the example of magnetic nanotubes in the vortex state. With increasing thickness, we observe the appearance of higher-order radial modes which are strongly hybridized and resemble the perpendicular-standing-waves (PSSWs) in flat films. Along with an increasing dispersion asymmetry, we uncover the curvature-induced non-reciprocity of the mode profiles. This is explained in a very simple picture general for thick curvilinear shells, considering the inhomogeneity of the emergent geometric volume charges along the thickness of the shell. Such curvature-induced mode-profile asymmetry also leads to non-reciprocal hybridization which can facilitate unidirectional spin-wave propagation. With that, we also show how curvature allows for nonlinear three-wave splitting of a higher-order radial mode into secondary modes which can also propagate unidirectionally. We believe that our study provides a significant contribution to the understanding of the spin-wave dynamics in curvilinear magnetic systems, but also advertises these for novel magnonic applications.

Keywords: spin waves; nanotubes; curvilinear magnetism; curvature effects; micromagnetic modeling; tetrax; nonreciprocity

Verknüpfte Publikationen


Mode splitting of spin waves in magnetic nanotubes with discrete symmetries

L. Körber, I. Kézsmárki, A. Kakay

We investigate how geometry influences spin dynamics in polygonal magnetic nanotubes. We find that lowering the rotational symmetry of nanotubes, by decreasing the number of planar facets, splits an increasing number spin-wave modes, which are doubly degenerate in cylindrical tubes. This symmetry-governed splitting is distinct form the topological split recently observed in cylindrical nanotubes. Doublet modes, where the azimuthal period is half-integer or integer multiple of the number of facets, split to singlet pairs with lateral standing-wave profiles of opposing mirror-plane symmetries. Moreover, the polygonal geometry facilitates the hybridization of modes with different azimuthal periods but the same symmetry, manifested in avoided level crossings. These phenomena, unimaginable in cylindrical geometry, provide new tools to control spin dynamics on the nanoscale. Our concepts can be generalized to nano-objects of versatile geometries and order parameters, offering new routes to understand and engineer dynamic responses in mesoscale physics.

Keywords: Spin wave; magnon; micromagnetic modeling; symmetry; nanotubes; group theory; micromagnetism; tetrax

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Tuning of the Dzyaloshinskii-Moriya interaction by He+ion irradiation

H. T. Nembach, E. Jué, K. Potzger, J. Faßbender, T. J. Silva, J. M. Shaw

We studied the impact of He+ irradiation on the Dzyaloshinskii-Moriya interaction (DMI) in Ta/Co20Fe60B20/Pt/MgO
samples. We found that irradiation of 40 keV He+ ions increases the DMI by approximately 20% for fluences up to 2 × 1016
ions/cm2 before it decreases for higher fluence values. In contrast, the interfacial anisotropy shows a distinctly different
fluence dependence. To better understand the impact of the ion irradiation on the Ta and Pt interfaces with the
Co20Fe60B20 layer, we carried out Monte-Carlo simulations, which showed an expected increase in disorder at the
interfaces. A moderate increase in disorder increases the total number of triplets for the three-site exchange mechanism and
consequently increases the DMI. Our results demonstrate the significance of disorder for the total DMI.

Keywords: Dzyaloshinskii-Moriya interaction; Fluence dependence; Ions irradiation

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Depth-Adjustable Magnetostructural Phase Transition in Fe₆₀V₄₀Thin Films

M. S. Anwar, H. Cansever, B. Boehm, R. Gallardo, R. Hübner, S. Zhou, U. Kentsch, S. Rauls, B. Eggert, H. Wende, K. Potzger, J. Faßbender, K. Lenz, J. Lindner, O. Hellwig, R. Bali

Phase transitions occurring within spatially confined regions can be useful for generating nanoscale material property modulations. Here we describe a magneto-structural phase transition in a binary alloy, where a structural transition from short range order (SRO) to body centered cubic (bcc) results in the formation of depth-adjustable ferromagnetic layers, which reveal application-relevant magnetic properties of high saturation magnetitzation (Ms) and low Gilbert damping (α). Here we use Fe₆₀V₄₀ binary alloy films which transform from initially Ms = 17 kA/m (SRO structure) to 747 kA/m (bcc structure) driven by atomic displacements caused by penetrating ions. Simulations show that estimated ~1 displacement per atom triggers a structural transition, forming homogeneous ferromagnetic layers. The thickness of ferromagnetic layer increases as a step-like function of the ion-fluence. Microwave excitations of the ferromagnetic/non-ferromagnetic layered system reveals an α = 0.0027 ± 0.0001. The combination of nanoscale spatial confinement, low α and high Ms provide a pathway for the rapid patterning of magnetic and microwave device elements.

Keywords: Magneto-structural correlations; Phase transitions; Magnetic thin films; Ion-irradiation; Short-range order

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Magnetic Configuration Driven Femtosecond Spin Dynamics in Synthetic Antiferromagnets

S. S. P. K. A. de Anulekha, L. Koch, F. Samad, N. P. Surya, B. Benny, O. Hellwig, B. Anjan

Ultrafast demagnetization in diverse materials has sparked
immense research activities due to its captivating richness and contested
underlying mechanisms. Among these, the two most celebrated mechanisms
have been the spin-flip scattering (SFS) and spin transport (ST) of optically
excited carriers. In this work, we have investigated femtosecond laser-induced
ultrafast demagnetization in perpendicular magnetic anisotropy-based synthetic
antiferromagnets (p-SAFs) where [Co/Pt]n−1/Co multilayer blocks are separated
by Ru or Ir spacers. Our investigation conclusively shows that the ST of optically
excited carriers can have a significant contribution to the ultrafast demagnetization
in addition to SFS processes. Moreover, we have also achieved an active control
over the individual mechanisms by specially designing the SAF samples and
altering the external magnetic field and excitation fluence. Our study provides a
vital understanding of the underlying mechanism of ultrafast demagnetization in
synthetic antiferromagnets, which will be crucial in future research and
applications of antiferromagnetic spintronics.

Keywords: synthetic antiferromagnets; magnetic multilayers; ultrafast demagnetization; spin transport

Mechanism of femtosecond laser induced ultrafast demagnetization in ultrathin film magnetic multilayers

S. Pan, F. Ganss, S. Panda, G. Sellge, C. Banerjee, J. Sinha, O. Hellwig, A. Barman

Ever since its discovery ultrafast demagnetization has remained one of the most
intriguing research areas in magnetism. Here, we demonstrate that in [Co (tCo )/
Pd (0.9 nm)] 8 multilayers, the characteristic decay time in femtosecond time-
scale varies non-monotonically with tCo in the range 0.07 nm B tCo B 0.75 nm.
Further investigation reveals higher spin fluctuation at higher ratio of electron to
Curie temperature to be responsible for this. Microscopic three-temperature
modelling unravels a similar trend in the spin–lattice interaction strength, which
strongly supports our experimental observation. The knowledge of the fem-
tosecond magnetization decay mechanism in ultrathin ferromagnetic films is
unique and important for the advancement of fundamental magnetism besides
their potential applications in ultrahigh speed spintronic devices.

Terahertz charge and spin transport in metallic ferromagnets: The role of crystalline and magnetic order

K. Neeraj, A. Sharma, M. Almeida, P. Matthes, F. Samad, G. Salvan, O. Hellwig, S. Bonetti

We study the charge and spin dependent scattering in a set of CoFeB thin films whose crystalline order is systematically enhanced and
controlled by annealing at increasingly higher temperatures. Terahertz conductivity measurements reveal that charge transport closely
follows the development of the crystalline phase, with the increasing structural order leading to higher conductivity. The terahertz-induced
ultrafast demagnetization, driven by spin-flip scattering mediated by the spin–orbit interaction, is measurable in the pristine amorphous sam-
ple and much reduced in the sample with the highest crystalline order. Surprisingly, the largest demagnetization is observed at intermediate
annealing temperatures, where the enhancement in spin-flip probability is not associated with an increased charge scattering. We are able to
correlate the demagnetization amplitude with the magnitude of the in-plane magnetic anisotropy, which we characterize independently, sug-
gesting a magnetoresistance-like description of the phenomenon.

Roadmap on Spin-Wave Computing

A. V. Chumak, P. Kabos, M. Wu, et al., H. Schultheiß, K. Schultheiß

Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.

Keywords: Spin wave; Magnon; Magnonics; Computing; Data processing

State-resolved ultrafast charge and spin dynamics in [Co/Pd] multilayers

L. Le Guyader, D. J. Higley, M. Pancaldi, T. Liu, Z. Chen, T. Chase, P. W. Granitzka, G. Coslovich, A. A. Lutman, G. L. Dakovski, W. F. Schlotter, P. Shafer, E. Arenholz, O. Hellwig, M. L. M. Lalieu, B. Koopmans, A. H. Reid, S. Bonetti, J. Stöhr, H. A. Dürr

We use transient absorption spectroscopy with circularly polarized x-rays to detect laser-
excited hole states below the Fermi level and compare their dynamics with that of unoc-
cupied states above the Fermi level in ferromagnetic [Co/Pd] multilayers. While below
the Fermi level an instantaneous and significantly stronger demagnetization is observed,
above the Fermi level the demagnetization is delayed by 35 ± 10 fs. This provides a direct
visualization of how ultrafast demagnetization proceeds via initial spin-flip scattering of
laser-excited holes to the subsequent formation of spin waves

Quantifying the Dzyaloshinkii-Moriya Interaction Induced by the Bulk Magnetic Asymmetry

Q. Zhang, J. Liang, K. Bi, L. Zhao, H. Bai, Q. Cui, H.-A. Zhou, H. Bai, H. Feng, W. Song, G. Chai, O. Gladii, H. Schultheiß, T. Zhu, J. Zhang, Y. Peng, H. Yang, W. Jiang

A broken interfacial inversion symmetry in ultrathin ferromagnet/heavy metal (FM/HM) bilayers is generally believed to be a prerequisite for accommodating Dzyaloshinskii-Moriya interaction (DMI) and for stabilizing chiral spin textures. By contrast, we present an approach for engineering both the sign and amplitude of DMI in relatively thick films without involving interfacial asymmetry, which is achieved through incorporating the composition gradient-induced bulk magnetic asymmetry (BMA) combined with strong spin-orbit coupling (SOC). The pivotal roles of BMA and SOC are theoretically examined based on the three-site Fert-Lévy model and the first principles calculations. Experimentally, both the sign and amplitude of DMI in films with controllable composition gradients along the growth direction, in the presence/absence of SOC are studied by using a Brillouin light scattering spectroscopy. Our results suggest that the appreciable value of DMI (±0.15 mJ/m2) could be established through combining BMA and SOC into relatively thick films. It is expected that our findings may help to further understand chiral magnetism and to design novel non-collinear spin textures.

Keywords: Dzyaloshinskii-Moriya interaction; Brillouin light scattering; spin-wave non-reciprocity; bulk magnetic asymmetry; spin-orbit coupling


Dysprosium Liquid Metal Alloy Ion Source For Magnetic Nanostructures

L. Bischoff, N. Klingner, P. Mazarov, K. Lenz, R. Narkovic, W. Pilz, F. Meyer

Focused Ion Beam (FIB) processing has been established as a well-suited and promising technique in R&D in nearly all fields of nanotechnology for patterning and prototyping on the μm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent an alternative to expand the FIB application fields beside all other source concepts. Especially ions from the rare earth (RE) element Dy is very interesting for local modification of magnetic properties like RE-induced damping in metallic alloys. So various alloys for source preparation were investigated. A promising solution was found in a Cu30Dy70 based LMAIS which should be introduced in more detail.

Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Source; Dysprosium; magnetic properties

Verknüpfte Publikationen

  • Open Access Logo Journal of Vacuum Science & Technology B 40(2022)5, 052802-1-052802-6
    DOI: 10.1116/6.0001837

Magnetic separation of rare-earth ions: property database and Kelvin force distribution

Z. Lei, B. Fritzsche, R. Salikhov, K. Schwarzenberger, O. Hellwig, K. Eckert

This work bridges two gaps in the magnetic separation of rare-earth ions. 1) A material property database is provided for the solutal expansion coefficient and the magnetic susceptibility of eleven out of seventeen trivalent rare-earths. 2) A novel protocol is developed to enhance and resolve the magnetic term of the Kelvin force. For that purpose, an assembly of partition magnets is created where the individual magnets function in the first quadrant of their magnetic hysteresis loop. The mutual reinforcement is quantified in a particle magnetic levitation system. Thus, compared to exisiting magnetic assemblies, an enhancement in $\frac{\partial B^2}{2 \mu_0 \partial z}$ as high as 2 orders of magnitudes is realized that covers 90\% of the normalized spatial scale and requires 1 order of magnitude less magnet mass. Modeling the energy density field makes it possible to quantify the equilibrium position of the particle cloud at rest, which is attained via magnetophoresis of the particles regardless of their initial position. This enables the magnetic trapping and manipulation of particles with small hydrodynamic diameters. Optically tracking the transient magnetophoresis enables a high-fidelity, sub-mm resolution of $\frac{\partial \bm{B}^2}{2 \mu_0 \partial z}$ which is further used to quantify the magnetic susceptibility of Ho(III), Tb(III), Er(III) and Gd(III).

Keywords: rare-earth; molar magnetic susceptibility; diamagnetic; Kelvin force; magnetic levitation


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Superparamagnetism and ferrimagnetism in the Sr2FeMoO6–δ nanoscale powder

N. Kalanda, M. Yarmolich, A. Burko, A. Temirov, A. Kislyuk, S. Demyanov, K. Lenz, J. Lindner, D.-H. Kim

As a result of using combined synthesis modes and optimized conditions for ultrasonic dispersion, a single-phase nanosized Sr2FeMoO6–δ powder with a high degree of superstructural ordering of Fe/Mo cations (88%) with an average grain size of 70.8 nm was obtained. Based on the results of Mössbauer spectroscopy and magnetic measurements, it was established that the obtained nanosized strontium ferromolybdate powder is in a magnetically inhomogeneous state, consisting of superparamagnetic and ferrimagnetic phases. The ferrimagnetic component of magnetization is characterized by higher values of magnetization in comparison with the superparamagnetic component, and a smooth increase is noted for this component, which reaches saturation with decreasing temperature. It is shown that there is no exchange magnetic interaction between superparamagnetic grains in the superparamagnetic phase, which made it possible, based on the Neel-Brown model, to estimate the critical sizes of nanoparticles, dSPM, in the single-domain state. The obtained dSPM values are smaller than the sizes of single-domain particles, which confirms the absence of a frozen state in some of the superparamagnetic particles. The results of this work are important for understanding the effect of nanosized grains on the magnetic properties and features of magnetization of the Sr2FeMoO6–δ polydisperse powder that is very promising for spintronic device application.

Keywords: Perovskites; sol-gel processes; electron microscopy; magnetic properties


  • Zweitveröffentlichung erwartet ab 15.08.2023

Control of site occupancy by variation of the Zn and Al content in NiZnAl ferrite epitaxial films with low magnetic damping

J. Lumetzberger, V. Ney, A. Zhakarova, D. Primetzhofer, K. Lenz, A. Ney

The structural and magnetic properties of Zn/Al doped nickel ferrite thin films can be adjusted by changing the Zn and Al content. The films are epitaxially grown by reactive magnetron sputtering using a triple cluster system to sputter simultaneously from three different targets. Upon the variation of the Zn content the films remain fully strained with similar structural properties, while the magnetic properties are strongly affected. The saturation magnetization and coercivity as well as resonance position and linewidth from ferromagnetic resonance (FMR) measurements are altered depending on the Zn content in the material. The reason for these changes can be elucidated by investigation of the x-ray magnetic circular dichroism spectra to gain site and valence specific information with elemental specificity. Additionally, from a detailed investigation by broadband FMR a minimum in g-factor and linewidth could be found as a function of film thickness. Furthermore, the results from a variation of the Al content using the same set of measurement techniques is given. Other than for Zn, the variation of Al affects the strain and even more pronounced changes to the magnetic properties are apparent.

Keywords: Spinel; Ferromagnetic resonance; damping; epitaxial films; XMCD; Ferrites


Curvature-induced drift and deformation of magnetic skyrmions: Comparison of the ferromagnetic and antiferromagnetic cases

K. Yershov, A. Kakay, V. P. Kravchuk

The influence of the geometrical curvature of chiral magnetic films on the static and dynamic properties of hosted skyrmions are studied theoretically. We predict the effects of the curvature-induced drift of skyrmions under the action of the curvature gradients without any external stimuli. The strength of the curvature-induced driving force essentially depends on the skyrmion type, N\'eel or Bloch, while the trajectory of motion is determined by the type of magnetic ordering: ferro- or antiferromagnetic. During the motion along the surface, skyrmions experience deformations which depend on the its type. In the small-curvature limit, using the collective-variable approach we show, that the driving force acting on a N{\'e}el skyrmion is linear with respect to the gradient of the mean curvature. The driving acting on a Bloch skyrmion is much smaller: it is proportional to the product of the mean curvature and its gradient. In contrast to the fast N{\'e}el skyrmions, the dynamics of the slow Bloch skyrmions is essentially affected by the skyrmion profile deformation. For the sake of simplicity we restrict ourselves to the case of zero Gaussian curvature and consider cylindrical surfaces of general type. Equations of motion for ferromagnetic and antiferromagnetic skyrmions in curved magnetic films are obtained in terms of collective variables. All analytical predictions are confirmed by numerical simulations.

Keywords: skyrmions; curvature effects; ferromagnetic; antiferromagnetic; dynamics


Spin pumping at interfaces with ferro- and paramagnetic Fe60Al40 films acting as spin source and spin sink

T. Strusch, K. Lenz, R. Meckenstock, R. Bali, J. Ehrler, J. Lindner, J. Faßbender, M. Farle, K. Potzger, A. Semisalova

We present a study of spin pumping efficiency and determine the spin mixing conductance and spin diffusion length in thin bilayer films based on 3d transition metal alloy Fe60Al40. Due to its magnetostructural phase transition, Fe60Al40 can be utilized as a ferromagnetic (FM) or paramagnetic (PM) material at the same temperature depending on its structural order, thus thin Fe60Al40 film can act as a spin source or a spin sink when interfaced with a paramagnet or a ferromagnet, correspondingly. Ferromagnetic resonance (FMR) measurements were performed in a frequency range of 5 - 35 GHz on bilayer films composed of FM-Fe60Al40 / Pd and PM-Fe60Al40 / permalloy Ni80Fe20. The increase of damping parameter with the thickness of paramagnetic layer was interpreted as a result of spin pumping into a paramagnet. In the first case, the FM-Fe60Al40 acts as a spin source and in the second case PM-Fe60Al40 serves as a spin sink. We determine the spin mixing conductance 𝑔𝑃𝑑↑↓=(3.8±0.5)×1018 m-2 at the FM-Fe60Al40/Pd interface and the spin diffusion length 𝜆𝑃𝑑=9.1 ±2.0 nm in Pd. For the PM-Fe60Al40/permalloy interface we find a spin mixing conductance 𝑔𝐹𝑒𝐴𝑙↑↓=(2.1±0.2)×1018 m-2 and a spin diffusion length 𝜆𝐹𝑒𝐴𝑙=11.9 ±0.2 nm for PM-Fe60Al40. Demonstrated bi-functionality of Fe60Al40 alloy in spin pumping structures may be promising for spintronic applicat

Keywords: Ferromagnetic resonance; spin pumping; ferromagnetic films; ferromagnetism; FeAl alloys; spin diffusion; damping; linewidth

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Nonstationary spin waves in a single rectangular permalloy microstrip under uniform magnetic excitation

S. Pile, S. Stienen, K. Lenz, R. Narkovic, S. Wintz, J. Förster, S. Mayr, M. Buchner, M. Weigand, V. Ney, J. Lindner, A. Ney

The ferromagnetic resonance modes in a single rectangular Py microstrip were directly imaged using timeresolved STXM-FMR measurements and the findings were corroborated by micromagnetic simulations. The spin wave resonance modes showed a nonstanding character, when the wave-vector is parallel to the external static magnetic field due to the highly inhomogeneous effective field inside the strip. The propagating character is observed for all the observed spin waves. The influence of the edge quality was analyzed using micromagnetic simulations.

Keywords: ferromagnetic resonance; scanning x-ray transmission microscopy; spin waves; nanostructures; micromagnetism

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Resonance behavior of embedded and freestanding microscale ferromagnets

H. Cansever, M. S. Anwar, S. Stienen, K. Lenz, R. Narkovic, G. Hlawacek, K. Potzger, O. Hellwig, J. Faßbender, J. Lindner, R. Bali

The ferromagnetic resonance of a disordered A2 Fe60Al40 of ferromagnetic strip, of dimensions 5 µm × 1 µm x 32 nm, has been observed in two vastly differing surroundings: in the first case, the ferromagnetic region was circumferenced by ordered B2 Fe60Al40, and in the second case it was free standing, adhering only to the oxide substrate. The embedded ferromagnet possesses a periodic magnetic domain structure, which transforms to a single domain structure in the freestanding case. The two cases differ in their dynamic response, for instance, the resonance field for the uniform (k = 0) mode at ~ 14 GHz excitation displays a shift from 209 to 194 mT, respectively for the embedded and freestanding cases, with the external magnetic field applied along the long axis. The resonant behavior of a microscopic ferromagnet can thus be finely tailored via control of its near-interfacial surrounding.

Keywords: Embedded nanomagnets; microresonator; ferromagnetic resonance; ion irradiation

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New dimension in magnetism and superconductivity: 3D and curvilinear nano-architectures

D. Makarov, O. Volkov, A. Kakay, O. Pylypovskyi, B. Budinska, O. Dobrovolskiy

Traditionally, the primary field, where curvature has been at the heart of research, was the theory of general relativity. In recent studies, however, the
impact of curvilinear geometry enters various disciplines, ranging from solid-state physics over soft-matter physics, chemistry and biology to mathematics,
giving rise to a plethora of emerging domains such as curvilinear nematics, curvilinear studies of cell biology, curvilinear semiconductors,
superfluidity, optics, two-dimensional van der Waals materials, plasmonics, magnetism and superconductivity. Here, we summarize the state of the art
and outline prospects for future research in curvilinear solid-state systems exhibiting such fundamental cooperative phenomena as ferromagnetism,
antiferromagnetism and superconductivity. Highlighting the recent developments and current challenges in theory, fabrication and characterization of
curvilinear micro- and nanostructures, special attention is paid to perspective research directions entailing new physics and to their strong application
potential. Overall, the perspective is aimed at crossing the boundaries between the magnetism and superconductivity communities and drawing attention
to the conceptual aspects of how extension of structures into the third dimension and curvilinear geometry can modify existing and aid launching
novel functionalities. In addition, the perspective should stimulate the development and dissemination of R&D-oriented techniques to facilitate rapid
transitions from laboratory demonstrations to industry-ready prototypes and eventual products.

Keywords: curvature effects in magnetism; curvature effects in superconductivity

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Spin-wave frequency combs

T. Hula, K. Schultheiß, F. J. Trindade Goncalves, L. Körber, M. Bejarano, M. Copus, L. Flacke, L. Liensberger, A. Buzdakov, A. Kakay, M. Weiler, R. Camley, J. Faßbender, H. Schultheiß

We experimentally demonstrate the generation of spin-wave frequency combs based on the non-
linear interaction of propagating spin waves in a microstructured waveguide. By means of time- and space-resolved Brillouin light scattering spectroscopy, we show that the simultaneous excita- tion of spin waves with different frequencies leads to a cascade of four-magnon scattering events which ultimately results in well-defined frequency combs. Their spectral weight can be tuned by the choice of amplitude and frequency of the input signals. Furthermore, we introduce a model for stimulated four-magnon scattering which describes the formation of spin-wave frequency combs in the frequency and time domain.

Keywords: magnetism; magnetization dynamics; spin waves; magnons; spin dynamics; micromagnetic modeling; Brillouin light scattering; spectroscopy

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Laser induced crystallization of Co–Fe–B films

M. Almeida, A. Sharma, P. Matthes, N. Köhler, S. Busse, M. Müller, O. Hellwig, A. Horn, D. R. T. Zahn, G. Salvan, S. E. Schulz

Local crystallization of ferromagnetic layers is crucial in the successful realization of miniaturized
tunneling magnetoresistance (TMR) devices. In the case of Co–Fe–B TMR devices, used most
successfully so far in applications and devices, Co–Fe–B layers are initially deposited in an amorphous
state and annealed post-deposition to induce crystallization in Co–Fe, thereby increasing the device
performance. In this work, first direct proof of locally triggered crystallization of 10 nm thick Co–Fe–B
films by laser irradiation is provided by means of X-ray diffraction (XRD) using synchrotron radiation.
A comparison with furnace annealing is performed for benchmarking purposes, covering different
annealing parameters, including temperature and duration in the case of furnace annealing, as
well as laser intensity and scanning speed for the laser annealing. Films of Co–Fe–B with different
stoichiometry sandwiched between a Ru and a Ta or MgO layer were systematically assessed by XRD
and SQUID magnetometry in order to elucidate the crystallization mechanisms. The transformation
of Co–Fe–B films from amorphous to crystalline is revealed by the presence of pronounced CoFe(110)
and/or CoFe(200) reflexes in the XRD θ-2θ scans, depending on the capping layer. For a certain window
of parameters, comparable crystallization yields are obtained with furnace and laser annealing.
Samples with an MgO capping layer required a slightly lower laser intensity to achieve equivalent Co–
Fe crystallization yields, highlighting the potential of laser annealing to locally enhance the TMR ratio.

Noncollinear Remanent Textures Induced by Surface Spin Flop in Synthetic Antiferromagnets with Perpendicular Anisotropy

B. Böhm, L. Fallarino, D. Pohl, B. Rellinghaus, O. Hellwig

The surface spin flop, observed in synthetic antiferromagnets (SAFs) with uniaxial anisotropy and
strong antiferromagnetic (AF) interlayer exchange coupling, can be considered as a laterally homoge-
neous, vertical AF domain wall pushed into the SAF from either the top or the bottom in the presence
of a strong external vertical magnetic field. As a result, the AF domain wall can be described as a one-
dimensional entity. In this work, we present a concept to stabilize laterally homogeneous vertical AF
domain walls by local variation of the perpendicular magnetic anisotropy in Co/Pt-based SAFs. Our
approach not only allows the stabilization of the vertical AF domain wall in the absence of any exter-
nal magnetic field, but furthermore enables a deterministic selection among four different remanent states,
each one stable within a broad external magnetic field range of almost one tesla. We also demonstrate an
extension to our concept by stabilizing two coexisting vertical AF domain walls, thus yielding a system
with a total of six different selectable (and reprogrammable) remanent states. The controlled stabiliza-
tion of noncollinear AF textures in the form of vertical AF domain walls at remanence could be used as
an infrastructure for propagating spin waves within the AF domain wall itself, as well as for tuning the
dynamic behavior of perpendicular standing spin wave modes existing vertically across the SAF.

CoCrFeNi High-Entropy Alloy Thin Films Synthesised by Magnetron Sputter Deposition from Spark Plasma Sintered Targets

H. Schwarz, T. Uhlig, N. Rösch, T. Lindner, F. Ganss, O. Hellwig, T. Lampke, G. Wagner, T. Seyller

Two magnetron sputter targets of CoCrFeNi High-Entropy Alloy (HEA), both in equal atomic ratio, were prepared by spark plasma sintering. One of the targets was fabricated from a homogeneous HEA powder produced via gas atomisation; for the second target, a mixture of pure element powders was used. Economic benefits can be achieved by mixing pure powders in the intended ratio in comparison to the gas atomisation of the specific alloy composition. In this work, thin films deposited via magnetron sputtering from both targets are analysed. The surface elemental composition is investigated by X-ray photoelectron spectroscopy, whereas the bulk stoichiometry is measured by X-ray fluorescence spectroscopy. Phase information and surface microstructure are investigated using X-ray diffraction and scanning electron microscopy, respectively. It is demonstrated that the stoichiometry, phase composition and microscopic structure of the as-deposited HEA thin films are almost identical if the same deposition parameters are used.

Keywords: high-entropy alloy; magnetron sputtering; spark plasma sintering; X-ray photoelectron spectroscopy; X-ray diffraction; scanning electron microscopy

Nondiffusive Transport and Anisotropic Thermal Conductivity in High-Density Pt/Co Superlattices

M. Shahzadeh, O. Andriyevska, R. Salikhov, L. Fallarino, O. Hellwig, S. Pisana

Despite the numerous reports over the last two decades dedicated to the study of interfacial thermal transport,
physics of thermal transport across nanoscale metallic multilayers is less explored. This is in part due to the relatively
high conductance characteristic of these interfaces, which renders them difficult to characterize.
Interfacial transport in these systems has so far appeared to be diffusive, a surprising behavior when the interface density
increases and the layer thicknesses become comparable with the mean free path of electrons.
To address the limit of diffusive theories describing heat transport across high-density metallic interfaces,
we systematically investigate heat transport in and across Pt/Co multilayers via frequency domain thermoreflectance.
Sensitivity gained from offsetting the laser beam and reducing the laser spot size allows for the
measurement of anisotropic thermal conductivity of the multilayers. By changing the number of interfaces while keeping the overall
thickness of Pt and Co in the multilayer structure constant, the effect of interface density on the multilayers’ effective thermal
conductivity is studied. The extracted Pt/Co interface thermal boundary conductance is then compared to the calculations from the
electronic diffuse mismatch model and experimental data available in the literature. We show that as the multilayer period thickness
becomes much smaller than the electron mean free path, measurements markedly deviate from the diffusive transport theory. We
attribute this deviation to the nondiffusive nature of heat transport in subnanometric scales at interface densities above 1/nm.

Keywords: heat transport; metallic multilayers; anisotropic thermal conductivity; nondiffusive transport; frequency domain thermoreflectance

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Spin-wave focusing induced by dipole-dipole interaction in synthetic antiferromagnets

R. A. Gallardo, P. Alvarado-Seguel, A. Kákay, J. Lindner, P. Landeros

Under certain conditions, spin waves can be channeled into a broad angular spectrum of wave vectors, where the direction
of the group velocity becomes independent of those wave vectors. Such highly focused waves are called caustic waves,
whose properties can be manipulated by anisotropies or chiral interactions, like the Dzyaloshinskii-Moriya interaction. In this
paper, we theoretically study the focusing features of the spin waves induced by the dipole-dipole interaction in synthetic
antiferromagnets. For stacked systems, the dipolar interaction causes a noticeable frequency nonreciprocity when the
magnetizations in both films are antiparallelly aligned, and then the focusing properties of the spin waves are enhanced. The
role of thicknesses and magnetic graduation along the film's normal are systematically analyzed. We found that the degree
of focalization of the spin waves can be manipulated by increasing the layers' thickness. Also, we show that the low- and
high-frequency modes exhibit different focalization properties; the low-frequency mode manifests a similar behavior to the
heavy-metal/ferromagnet systems with interfacial Dzyaloshinskii-Moriya interaction, while the high-frequency one tends the
generate almost reciprocal interference patterns along one axis. In the case of magnetization-graded synthetic
antiferromagnets, we demonstrate that the graduation slightly influences the low-frequency mode, while the focusing and
nonreciprocal dynamic properties of the high-frequency ones are notoriously altered. The theoretical calculations are
compared with micromagnetic simulations, where a good agreement is found between both methods. Our results
demonstrate that a synthetic antiferromagnetic system allows for controlling the propagation of spin waves, assisting in the
transfer of angular momentum and energy.

Keywords: Spin waves; Wave focusing; synthetic antiferromagnets; Dzyaloshinskii-Moriya interaction; Spectrum analysis; dipole-dipole interaction; multilayers


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Robust formation of nanoscale magnetic skyrmions in easy-plane anisotropy thin film multilayers with low damping

L. Flacke, V. Ahrens, S. Mendisch, L. Körber, T. Böttcher, E. Meidinger, M. Yaqoob, M. Müller, L. Liensberger, A. Kakay, M. Becherer, P. Pirro, M. Althammer, S. Geprägs, H. Huebl, R. Gross, M. Weiler

We experimentally demonstrate the formation of room-temperature skyrmions with radii of about 25 nm in easy-plane anisotropy multilayers with an interfacial Dzyaloshinskii-Moriya interaction (DMI). We detect the formation of individual magnetic skyrmions by magnetic force microscopy and find that the skyrmions are stable in out-of-plane fields up to about 200 mT. We determine the interlayer exchange coupling as well as the strength of the interfacial DMI. Additionally, we investigate the dynamic microwave spin excitations by broadband
magnetic resonance spectroscopy. From the uniform Kittel mode we determine the magnetic anisotropy and lowdamping α < 0.04. We also find clear magnetic resonance signatures in the nonuniform (skyrmion) state. Our findings demonstrate that skyrmions in easy-plane multilayers are promising for spin-dynamical applications.

Keywords: skyrmion; ferromagnetic resonance; DMI; low damping


Control of Stripe-Domain-Wall Magnetization in Multilayers Featuring Perpendicular Magnetic Anisotropy

R. Salikhov, F. Samad, B. Böhm, S. Schneider, D. Pohl, B. Rellinghaus, A. Ullrich, M. Albrecht, J. Lindner, N. S. Kiselev, O. Hellwig

We report on the controlled switching of domain-wall (DW) magnetization in aligned stripe-domain
structures, stabilized in [Co(0.44 nm)/Pt(0.7 nm)]X (X = 48, 100, 150) multilayers with perpendicular
magnetic anisotropy. The switching process, induced by an external magnetic field, is monitored by measuring the evolution of the in-plane magnetization. We show that the remanent in-plane magnetization originates from the polarization of the Bloch-type DWs. With micromagnetic simulations, we reveal that
the reversal of the DW polarization is the result of the emergence and collapse of horizontal Bloch lines
within the DWs at particular strengths of the external magnetic field, applied opposite to the DW polarization. Our findings are relevant for DW-based magnonics and bubble-skyrmion applications in magnetic multilayers.

Keywords: Magnetic domains; Domain walls; Magnetization switching; Skyrmions; Spintronics; Micromagnetism


Symmetry and curvature effects on spin waves in vortex-state hexagonal nanotubes

L. Körber, M. Zimmermann, S. Wintz, S. Finizio, M. Kronseder, D. Bougeard, F. Dirnberger, M. Weigand, J. Raabe, J. A. Otálora, H. Schultheiß, E. Josten, J. Lindner, I. Kézsmárki, C. H. Back, A. Kakay

Analytic and numerical studies on curved magnetic nano-objects predict numerous exciting effects that can be referred to as magneto-chiral effects, which do not originate from intrinsic Dzyaloshinskii–Moriya interaction or interface-induced anisotropies. In constrast, these chiral effects stem from isotropic exchange or dipole-dipole interaction, present in all magnetic materials, which acquire asymmetric contributions in case of curved geometry of the specimen. As a result, for example, the spin-wave dispersion in round magnetic nanotubes becomes asymmetric, namely spin waves of the same frequency propagating in opposite directions along the nanotube exhibit different wavelenghts. Here, using time-resolved scanning transmission X-ray microscopy experiments, standard micromagntic simulations and a dynamic-matrix approach, we show that the spin-wave spectrum undergoes additional drastic changes when transitioning from a continuous to a discrete rotational symmetry, i.e. from round to hexagonal nanotubes, which are much easier to fabricate. The polygonal shape introduces localization of the modes both to the sharp, highly curved corners and flat edges. Moreover, due to the discrete rotational symmetry, the degenerate nature of the modes with azimuthal wave vectors known from round tubes is partly lifted, resulting in singlet and duplet modes. For comparison with our experiments, we calculate the microwave absorption from the numerically obtained mode profiles which shows that a dedicated antenna design is paramount for magnonic applications in 3D nano-structures. To our knowledge these are the first experiments directly showing real space spin-wave propagation in 3D nano objects.

Keywords: spin wave; dispersion; curvature; micromagnetic modeling; hexagonal; symmetry; STXM

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Numerical reverse engineering of general spin-wave dispersions: Bridge between numerics and analytics using a dynamic-matrix approach

L. Körber, A. Kakay

Modern problems in magnetization dynamics require more and more the numerical determination of the spin-wave spectra and -dispersion in magnetic systems where analytic theories are not yet available. Micromagnetic simulations can be used to compute the spatial mode profiles and oscillation frequencies of spin-waves in magnetic system with almost arbitrary geometry and different magnetic interactions. Although numerical approaches are very versatile, they often do not give the same insight and physical understanding as analytical theories. For example, it is not always possible to decide whether a certain feature (such as dispersion asymmetry, for example) is governed by one magnetic interaction or the other. Moreover, since numerical approaches typically yield the normal modes of the system, it is not always feasible to disentangle hybridized modes. In this manuscript, we build a bridge between numerics and analytics by presenting a methodology to calculate the individual contributions to general spin-wave dispersions in a fully numerical manner. We discuss the general form of any spin-wave dispersion in terms of the effective (stiffness) fields produced by the modes. Based on a special type of micromagnetic simulation, the numerical dynamic-matrix approach, we show how to calculate each stiffness field in the respective dispersion law, separately for each magnetic interaction. In particular, it becomes possible to disentangle contributions of different magnetic interactions to the dispersion asymmetry in systems where non-reciprocity is present. At the same time, dipolar-hybridized modes can be easily disentangled. Since this methodology is independent of the geometry or the involved magnetic interactions at hand, we believe it is attractive for experimental and theoretical studies of magnetic systems where there are no analytics available yet, but also to aid the development of new analytical theories.

Keywords: spin wave; Micromagnetic simulations; theory; dispersion; dynamic-matrix approach; normal modes; hybridization; numerics


Effects of hydrogen absorption on magnetism in Ni80Fe20/Y/Pd trilayers

C. Weiss, R. Hübner, M. Saunders, A. Semisalova, J. Ehrler, N. Schmidt, J. Seyd, M. Albrecht, S. Anwar, J. Lindner, K. Potzger, M. Kostylev

The effects of hydrogen absorption on the effective magnetization (4πMeff), gyromagnetic ratio (γ), Gilbert damping constant (αG), and the inhomogeneous linewidth broadening in Py(x)/Y(16 nm)/Pd(15 nm) trilayer films (x = 2, 3, 5, 8, 10, 20, 40 nm) were investigated with ferromagnetic resonance (FMR), transmission electron microscopy, and vibrating sample magnetometry. In the presence of a hydrogen atmosphere, the samples show a reduction of their FMR linewidth which is found to stem purely from a reduction of the inhomogeneous linewidth broadening. This is attributed to a rearrangement of atoms at the Py/Y interface in the presence of hydrogen, making the Py/Y interface more homogeneous. In addition, a reduction of 4πMeff was seen for all samples in the hydrogen atmosphere which is typical for an increase of the interfacial perpendicular magnetic anisotropy at the Py/Y interface.

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Stress-induced modification of gyration dynamics in stacked double-vortex structures studied by micromagnetic simulations

V. Iurchuk, L. Körber, A. M. Deac, J. Faßbender, J. Lindner, A. Kakay

In this paper, using micromagnetic simulations, we investigate the stress-induced frequency tunability of double-vortex nano-oscillators comprising magnetostrictive and non-magnetostrictive ferromagnetic layers separated vertically by a non-magnetic spacer. We show that the relative orientations of the vortex core polarities p1 and p2 have a strong impact on the eigen-frequencies of the dynamic modes. When the two vortices with antiparallel polarities have different eigen-frequencies and the magnetostatic coupling between them is sufficiently strong, the stress-induced magnetoelastic anisotropy can lead to the single-frequency resonant gyration mode of the two vortex cores. Additionally, for the case of parallel polarities, we demonstrate that for sufficiently strong magnetostatic coupling, the magnetoelastic anisotropy leads to the coupled vortex gyration in the chaotic regime and to the lateral separation of the vortex core trajectories. These findings offer a path for achieving a fine control over gyration frequencies and trajectories in vortex-based oscillators via adjustable elastic stress, which can be easily generated and tuned electrically, mechanically or optically.

Keywords: Magnetic vortex; Magnetization dynamics; Magnetoelastic anisotropy; Micromagnetic modelling

Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

F. Samad, G. Hlawacek, S. S. P. K. Arekapudi, X. Xu, L. Koch, M. Lenz, O. Hellwig

We study layered synthetic antiferromagnets (SAFs) with out-of-plane interface anisotropy, where the layer-wise antiferromagnetic (AF)
alignment is induced by interlayer exchange coupling (IEC). By applying low energy He+ focused ion beam irradiation to the SAF, a depth-dependent
reduction of the IEC and anisotropy can be achieved due to layer intermixing. As a consequence, after irradiation, a specific field
reversal sequence of the SAF is energetically preferred. When tuning the pristine SAF to exhibit an inverted field reversal, we are thus able to
create AF domains in the irradiated regions. When irradiated with a fluence gradient, these AF domains can be further deterministically
manipulated by an external magnetic field. Among other applications, this could be utilized for engineering a controllable and local magnetic
stray field landscape, for example, at AF domain walls, within the otherwise stray field free environment provided by the SAF.

Keywords: Bubble domains; Focused ion beam; Sputter deposition; Interlayer exchange coupling; Magnetic hysteresis

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Reconfigurable Spin-Wave Interferometer at the Nanoscale

J. Chen, H. Wang, T. Hula, C. Liu, S. Liu, T. Liu, H. Jia, Q. Song, C. Guo, Y. Zhang, J. Zhang, X. Han, D. Yu, M. Wu, H. Schultheiß, H. Yu

Spin waves with nanoscale wavelengths can transfer information free of electron transport and hence are promising for wave-based computing technologies with low-power consumption as a solution to the severe energy losses in modern electronics. Logic circuits based on the interference of spin waves have been proposed for more than a decade. However, spin-wave interference at the nanoscale has yet been realized. Here, we demonstrate experimentally the interference of spin waves with wavelengths down to 50 nm in a low-damping magnetic insulator. The constructive and destructive interference of spin waves is detected in the frequency domain using propagating spin-wave spectroscopy, which is further confirmed by the Brillouin light scattering. The interference pattern is found to be highly sensitive to the distance between two magnetic nanowires acting as spin-wave emitters. By controlling the magnetic configuration of the double-wire system, one can switch the spin-wave interferometer on and off. The observed phenomena are theoretically accounted for by the interlayer magnon-magnon coupling. Our demonstrations are thus key to the realization of spin-wave computing system based on non-volatile nanomagnets at the GHz frequencies.

Keywords: spin waves; magnetism; Brillouin spectroscopy; interferometer; interference; nanotechnologie

Nonreciprocity of spin waves in magnetic nanotubes with helical equilibrium magnetization

M. M. Salazar-Cardona, L. Körber, H. Schultheiß, K. Lenz, A. Thomas, K. Nielsch, A. Kakay, J. A. Otálora

Spin waves (SWs) in magnetic nanotubes have shown interesting nonreciprocal properties in their dispersion relation, group velocity, frequency linewidth, and attenuation lengths. The reported chiral effects are similar to those induced by the Dzyaloshinskii–Moriya interaction but originating from the dipole–dipole interaction. Here, we show that the isotropic-exchange interaction can also induce chiral effects in the SW transport; the so-called Berry phase of SWs. We demonstrate that with the application of magnetic fields, the nonreciprocity of the different SW modes can be tuned between the fully dipolar governed and the fully exchange governed cases, as they are directly related to the underlying equilibrium state. In the helical state, due to the combined action of the two effects, every single sign combination of the azimuthal and axial wave vectors leads to different dispersions, allowing for a very sophisticated tuning of the SW transport. A disentangle- ment of the dipole–dipole and exchange contributions so far was not reported for the SW transport in nanotubes. Furthermore, we propose a device based on coplanar waveguides that would allow to selectively measure the exchange or dipole induced SW nonreciprocities. In the context of magnonic applications, our results might encourage further developments in the emerging field of 3D magnonic devices using curved magnetic membranes.

Keywords: spin wave; nanotube; nonreciprocity; transducer


Multistate current-induced magnetization switching in Au/Fe/MgO(001) epitaxial heterostructures

P. Gospodarič, E. Młyńczak, I. Soldatov, A. Kakay, D. E. Bürgler, L. Plucinski, R. Schäfer, J. Faßbender, C. M. Schneider

Magnetization switching using in-plane charge current recently has been widely investigated in heavy metal/ferromagnet bilayers with the switching mechanism usually attributed to the action of the spin-orbit coupling. Here we study in-plane current induced magnetization switching in model epitaxial bilayers that consist of Au(001) and Fe(001) grown on MgO(001). We use the planar Hall effect combined with magnetooptical Kerr effect (MOKE) microscopy to investigate magnetic properties of the bilayers and current-induced switching. We show that a current density beyond 1.4×10^7 A/cm can be employed for reproducible electrical switching of the magnetization between multiple stable states that correspond to different arrangements of magnetic domains with magnetization direction along one of the in-plane easy magnetization axes of the Fe(001) film. Lower current densities result in stable intermediate transversal resistances which are interpreted based on MOKE-microscopy investigations as resulting from the current-induced magnetic domain structure that is formed in the area of the Hall cross. We find that the physical mechanism of the current-induced magnetization switching of the Au/Fe/MgO(001) system at room temperature can be fully explained by the Oersted field, which is generated by the charge current flowing mostly through the Au layer.

Spin polarization and magnetotransport properties of systematically disordered Fe60Al40 thin films

K. Borisov, J. Ehrler, C. Fowley, B. Eggert, H. Wende, S. Cornelius, K. Potzger, J. Lindner, J. Faßbender, R. Bali, P. Stamenov

We investigate the evolution of spin polarization, spontaneous Hall angle (SHA), saturation magnetization and Curie temperature of B2-ordered Fe60Al40 thin films under varying antisite disorder, induced by Ne+-ion irradiation. The spin polarization increases monotonically as a function of ion fluence. A relatively high polarization of 46 % and the SHA of 3.1 % are achieved on 40 nm thick films irradiated with 2 ⋅ 1016 ions/cm2 at 30 keV. An interesting divergence in the trends of the magnetization and SHA is observed for low disorder concentrations. The high spin polarization and its broad tunability range make ion-irradiated Fe60Al40 a promising material for application in spin electronic devices.

Keywords: Spin polarization; Iron-Aluminium; Spintronics; Anomalous Hall Effect; Topological Hall effect; Irradiation effects; Thin films; Magnetometry; Andreev reflection

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Finite-element dynamic-matrix approach for spin-wave dispersions in magnonic waveguides with arbitrary cross section

L. Körber, G. Quasebarth, A. Otto, A. Kakay

We present a numerical approach to efficiently calculate spin-wave dispersions and spatial mode profiles in magnetic waveguides of arbitrarily shaped cross section with any non-collinear equilibrium magnetization which is translationally invariant along the waveguide. Our method is based on the propagating-wave dynamic-matrix approach by Henry et al. and extends it to arbitrary cross sections using a finite-element method. We solve the linearized equation of motion of the magnetization only in a single waveguide cross section which drastically reduces computational effort compared to common three-dimensional micromagnetic simulations. In order to numerically obtain the dipolar potential of individual spin-wave modes, we present a plane-wave version of the hybrid finite-element/boundary-element method by Frekdin and Koehler which, for the first time, we extend to a modified version of the Poisson equation. Our method is applied to several important examples of magnonic waveguides including systems with surface curvature, such as magnetic nanotubes, where the curvature leads to an asymmetric spin-wave dispersion. In all cases, the validity of our approach is confirmed by other methods. Our method is of particular interest for the study of curvature-induced or magnetochiral effects on spin-wave transport but also serves as an efficient tool to investigate standard magnonic problems.

Keywords: spin wave; eigensolver; micromagnetic simulation; dispersion; finite-element method; FEM

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Agility of spin Hall nano-oscillators

F. J. Trindade Goncalves, T. Hache, M. Bejarano, T. Hula, O. Hellwig, J. Faßbender, H. Schultheiß

We investigate the temporal response of constriction-based spin Hall nano-oscillators driven by pulsed stimuli using time-resolved Brillouin light scattering microscopy. The growth rate of the magnetization auto-oscillations, enabled by spin Hall effect and spin orbit torque, is found to vary with the amplitude of the input voltage pulses, as well as the synchronization frequency set by an external microwave input. The combination of voltage and microwave pulses allows to generate auto-oscillation signals with multi-level amplitude and frequency in the time-domain. Our findings suggest that the lead time of processes such as synchronization and logic using spin Hall nano-oscillators can be reduced to the nanosecond time-scale.

Keywords: Spintronics; Magnons; Spin waves; Brillouin scattering & spectroscopy; Microwave techniques

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Robustness of the remanent magnetic domain pattern formation and associated stripe-bubble transitions in Co/Pt multilayers against field sequencing

A. Gentillon, C. Richards, L. A. Ortiz-Flores, J. Metzner, D. Montealegre, M. Healey, K. Cardon, A. Westover, O. Hellwig, K. Chesnel

Thin ferromagnetic [Co/Pt] multilayers with perpendicular magnetic anisotropy exhibit a variety of nanoscopic magnetic domain patternsat remanence, from long interlaced stripes to lattices of bubbles, depending on the multilayer structure but also on the magnetic historyof the sample. For optimized structural parameters, stripe-bubble transitions accompanied by drastic increases in domain density havebeen observed when the magnitude of the previously applied perpendicular fieldHmis finely tuned throughout the hysteresis loop. Here, we investigate the robustness of these morphological transitions against field sequencing and field cycling. We conducted this study on[Co(x)/Pt(7Å)]N=50where x varies from 4 to 60 Å. We mapped the morphological transition withHmvarying from 0 to 9 T, following bothan ascending sequence (0→9 T) and a descending sequence (9 T→0). We found that the optimal fieldHm=H∗at which the domain densityis maximized and its associated maximal density n∗ are not significantly affected by the field sequencing direction. We have also investigatedpossible pumping effects when cycling the applied field at the value H∗. We found that n∗ remains relatively stable through field cycling, andmuch more stable in the bubble state, compared to longer stripe states. The observed robustness of these morphological transitions againstfield sequencing and field cycling is of crucial importance for potential magnetic recording applications.

Microresonators and Microantennas—tools to explore magnetization dynamics in single nanostructures

H. Cansever, J. Lindner

The phenomenon of magnetic resonance and its detection via microwave spectroscopy provide direct insight into the magnetization dynamics of bulk or thin film materials. This allows for direct access to fundamental properties, such as the effective magnetization, g-factor, magnetic anisotropy and the various damping (relaxation) channels that govern the decay of magnetic excitations. Cavity-based and broadband ferromagnetic resonance techniques that detect the microwave absorption of spin systems require a minimum magnetic volume to obtain a sufficient signal-to-noise ratio (S/N). Therefore, conventional techniques typically do not offer the sensitivity to detect individual micro- or nanostructures. A solution to this sensitivity problem is the so-called planar microresonator, which is able to detect even the tiniest absorption signals of magnetic nanostructures, including spin-wave or edge resonance modes. As an example, we describe the microresonator-based detection of spin-wave modes within microscopic strips of ferromagnetic A2 Fe60Al40 that are imprinted into a paramagnetic B2 Fe60Al40-matrix via focused ion-beam irradiation. While microresonators operate at a fixed microwave frequency, a reliable quantification of the key magnetic parameters like the g-factor or spin relaxation times requires investigations within a broad range of frequencies. In this study, we introduce and describe the step from microresonators towards a broadband microantenna approach. It allows for performing broadband magnetic resonance experiments on single nanostructured magnetic objects in a frequency range of 2-18 GHz. We employ this detection scheme to explore the influence of lateral structuring on the magnetization dynamics of a Permalloy strip.

Keywords: ferromagnetic resonance; microantenna; microresonator; magnetic relaxation; thin films; nanosctructures

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

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

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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The 2021 Magnonics Roadmap

A. Barman, G. Gubbiotti, S. Ladak, A. O. Adeyeye, M. Krawczyk, J. Gräfe, A. V. Chumak, A. Khitun, D. Nikonev, I. A. Young, V. I. Vasyuchka, B. Hillebrands, S. A. Nikitov, H. Yu, D. Grundler, A. V. Sadovnikov, A. A. Grachev, S. E. Sheshukova, J.-Y. Duquesne, M. Marangolo, G. Csaba, W. Porod, V. E. Demidov, S. Urazhdin, S. O. Demokritov, E. Albisetti, D. Petti, R. Bertacco, H. Schultheiß, V. V. Kruglyak, V. D. Poimanov, S. Sahoo, J. Sinha, T. Moriyama, S. Mizukami, H. Yang, M. Münzenburg, P. Landeros, R. A. Gallardo, G. Carlotti, J.-V. Kim, R. L. Stamps, R. E. Camley, B. Rana, Y. Otani, W. Yu, T. Yu, G. E. W. Bauer, C. Back, G. S. Uhrig, O. V. Dobrovolskiy, S. van Dijken, B. Budinska, H. Qin, C. Adelmann, S. Cotofana, A. Naeemi, B. W. Zingsem, M. Winklhofer

Magnonics is a rather young physics research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. After several papers and review articles published in the last decade, with a steadily increase in the number of citations, we are presenting the first Roadmap on Magnonics. This a collection of 22 sections written by leading experts in this field who review and discuss the current status but also present their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and the interconnections to standard electronics. In this respect, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This Roadmap represents a milestone for future emerging research directions in magnonics and hopefully it will be followed by a series of articles on the same topic.

Keywords: magnonics; spin waves; roadmap; spin textures; skyrmions; computing

Highly Tunable Magnetic and Magnetotransport Properties of Exchange Coupled Ferromagnet/Antiferromagnet-based Heterostructures

S. S. P. K. Arekapudi, D. Bülz, F. Ganss, F. Samad, F. Radu, D. R. T. Zahn, K. Lenz, G. Salvan, M. Albrecht, O. Hellwig

Antiferromagnets (AFMs) with zero net magnetization are proposed as active elements in future spintronic devices. Depending on the critical thickness of the AFM thin films and the measurement temperature, bimetallic Mn-based alloys and transition metal oxide-based AFMs can host various coexisting ordered, disordered, and frustrated AFM phases. Such coexisting phases in the exchange coupled ferromagnetic (FM)/AFM-based heterostructures can result in unusual magnetic and magnetotransport phenomena. Here, we integrate chemically disordered AFM γ-IrMn3 thin films with coexisting AFM phases into complex exchange coupled MgO(001)/γ-Ni3Fe/γ-IrMn3/γ-Ni3Fe/CoO heterostructures and study the structural, magnetic, and magnetotransport properties in various magnetic field cooling states. In particular, we unveil the impact of rotating the relative orientation of the disordered and reversible AFM moments with respect to the irreversible AFM moments on the magnetic and magnetoresistance properties of the exchange coupled heterostructures. We further found that the persistence of AFM grains with thermally disordered and reversible AFM order is crucial for achieving highly tunable magnetic properties and multi-level magnetoresistance states. We anticipate that the introduced approach and the heterostructure architecture can be utilized in future spintronic devices to manipulate the thermally disordered and reversible AFM order at the nanoscale.


Frequency- and magnetic-field-dependent properties of ordered magnetic nanoparticle arrangements

N. Neugebauer, T. Hache, M. T. Elm, D. M. Hofmann, C. Heiliger, H. Schultheiß, P. J. Klar

We present a frequency and magnetic field dependent investigation of ordered arrangements of 20 nm mag-netic nanoparticles (MNPs) consisting of magnetite (Fe3O4) by employing micro Brillouin light scatteringmicroscopy. We utilized electron beam lithography to prepare hexagonally arranged, circularly shaped MNP-assemblies consisting of a single layer of MNPs using a variant of the Langmuir-Blodgett technique. Bycomparing the results with non-structured, layered superlattices of MNPs, further insight into the influenceof size and geometry of the arrangement on the collective properties is obtained. We show that at low staticexternal field strengths, two signals occur in frequency dependent measurements for both non-structured andstructured assemblies. Enlarging the static external field strength leads to a sharpening of the main signal,while the satellite signal decreases in its intensity and increases in its linewidth. The occurrence of multiplesignals at low external field strengths is also confirmed by sweeping the static external field and keeping theexcitation frequency constant. Micromagnetic simulations unravel the origin of the different signals and theirdependence on the static external field strength, enabling an interpretation of the observed characteristics interms of different local environments of an MNPs forming the MNP assembly.

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Spin-wave dynamics and symmetry breaking in an artificial spin ice

S. Saha, J. Zhou, K. Hofhuis, A. Kakay, V. Scagnoli, L. J. Heyderman, S. Gliga

Artificial spin ices are periodic arrangements of interacting nanomagnets that have been successfully used to investigate emergent phenomena in the presence of geometric frustration. Recently, it has become clear that artificial spin ices equally have the potential to be used as building blocks for creating functional materials, such as magnonic crystals and ratchets, in addition to supporting a large number of programmable magnetic states. In this context, we investigate the magnetization dynamics in a system exhibiting asymmetric magnetostatic interactions owing to locally broken structural symmetry. We find that this gives rise to a rich spectrum that can be tuned through an external field. We also determine the evolution of the observed excitation modes, starting with building blocks and evolving into larger arrays, highlighting the role of symmetry breaking in defining the mode spectrum of the system. Concurrently, the increasing complexity of the spectrum leads to the existence of a large number of modes over a narrow range of frequencies. These results contribute to the understanding of magnetization dynamics in spin ice systems beyond the kagome and square ice geometries with a view towards the realization of reconfigurable magnonic crystals based on spin ices.

Keywords: artificial spin ice; symmetry breaking; spin-wave dynamics; reconfigurable; magnonic crystal

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Magnetic texture based magnonics

H. Yu, J. Xiao, H. Schultheiß

The spontaneous magnetic orders arising in ferro-, ferri- and antiferromagnets stem from various magnetic interactions. Depending on the interplay and competition among the Heisenberg exchange interaction, Dzyaloshinskii-Moriya exchange interaction, magnetic dipolar interaction and crystal anisotropies, a great variety of magnetic textures may be stabilized, such as magnetic domain walls, vortices, Skyrmions and spiral helical structures. While each of these spin textures responds to external forces in a specific manner with characteristic resonance frequencies, they also interact with magnons, the fundamental collective excitation of the magnetic order, which can propagate in magnetic materials free of charge transport and therefore with low energy dissipation. Recent theories and experiments found that the interplay between spin waves and magnetic textures is particularly interesting and rich in physics. In this review, we introduce and discuss the theoretical framework of magnons living on a magnetic texture background, as well as recent experimental progress in the manipulation of magnons via magnetic textures. The flexibility and reconfigurability of magnetic textures are discussed regarding the potential for applications in information processing schemes based on magnons.

Keywords: magnetic textures; spin waves; magnetization dynamics; Skyrmions; antiferromagnets; Dzyaloshinskii Moria; chiral magnetism; domain walls; vortices


Time refraction of spin waves

K. Schultheiß, N. Sato, P. Matthies, L. Körber, K. Wagner, T. Hula, O. Gladii, J. E. Pearson, A. Hoffmann, M. Helm, J. Faßbender, H. Schultheiß

We present an experimental study of time refraction of spin waves propagating in microscopic waveguides under the influence of time-varying magnetic fields. Using space- and time-resolved Brillouin light scattering microscopy, we demonstrate that the broken translational symmetry along the time coordinate can be used to in- or decrease the energy of spin waves during their propagation. This allows for a broadband and controllable shift of the spin-wave frequency. Using an integrated design of spin-wave waveguide and microscopic current line for the generation of strong, nanosecond-long, magnetic field pulses, a conversion efficiency up to 39% of the carrier spin-wave frequency is achieved, significantly larger compared to photonic systems. Given the strength of the magnetic field pulses and its strong impact on the spin-wave dispersion relation, the effect of time refraction can be quantified on a length scale comparable to the spin-wave wavelength. Furthermore, we utilize time refraction to excite spin-wave bursts with pulse durations in the nanosecond range and a frequency shift depending on the pulse polarity.

Keywords: magnetization dynamics; spin waves; time refraction; Brillouin light scattering


Numerical ferromagnetic resonance experiments in nanosized elements

K. Wagner, L. Körber, S. Stienen, J. Lindner, M. Farle, A. Kakay

We present a numerical approach to obtain the Ferromagnetic Resonance (FMR) spectra of micrometer- and nano-sized magnetic elements by micromagnetic simulations. Mimicking common experimental conditions, a static magnetic field is applied and a linearly polarized oscillating magnetic field is used to excite magnetization dynamics. A continuous single-frequency excitation is utilized, which permits to study the steady-state dynamics in space- and time-domain. This gives direct access to resonance fields, line widths and relative amplitudes as observed in the experiments, which is not easily accessible in pulsed schemes and allows for a one-to-one identification between simulation and experiment. Similar to numerical approaches using pulsed excitations the phases, ellipticity and spatial mode profiles of the spin-wave excitations may also be accessed. Using large excitation powers we then showcase that one can additionally study nonlinear responses by this method such as the nonlinear shift of the resonance fields and the fold-over of the absorption lines. Since the dynamic susceptibility is directly determined from standard outputs of common micromagnetic codes, the presented method is robust, efficient and easy-to-use, adding to its practical importance.

Keywords: Ferromagnetic resonance; Micromagnetic simulations; line width; nonlinear; fold-over

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Mapping the stray fields of a micromagnet using spin centers in SiC

M. Bejarano, F. J. Trindade Goncalves, M. Hollenbach, T. Hache, T. Hula, Y. Berencen, J. Faßbender, M. Helm, G. Astakhov, H. Schultheiß

We report the use of optically addressable spin qubits in SiC to probe the static magnetic stray fields generated by a ferromagnetic microstructure lithographically patterned on the surface of a SiC crystal. The stray fields cause shifts in the resonance frequency of the spin centers. The spin resonance is driven by a micrometer-sized microwave antenna patterned adjacent to the magnetic element. The patterning of the antenna is done to ensure that the driving microwave fields are delivered locally and more efficiently compared to conventional, millimeter-sized circuits. A clear difference in the resonance frequency of the spin centers in SiC is observed at various distances to the magnetic element, for two different magnetic states. Our results offer a wafer-scale platform to develop hybrid magnon-quantum applications by deploying local microwave fields and the stray field landscape at the micrometer lengthscale.

Keywords: Quantum sensing; Magnonics; Spin qubits in SiC; Microwave circuits; electron beam lithography

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  • Open Access Logo IEEE Magnetics Letters 12(2021), 9380379
    DOI: 10.1109/LMAG.2021.3066341
    Cited 1 times in Scopus
  • Poster (Online Präsentation)
    Magnetism and Magnetic Materials Conference 2020 (MMM2020), 02.-06.11.2020, Online, United States
  • Open Access Logo Poster (Online Präsentation)
    Around-the-Clock Around-the-Globe Magnetics Conference, 24.08.2021, Online, Online
  • Open Access Logo Poster (Online Präsentation)
    SKM DPG 2021, 27.09.-01.10.2021, Online, Online
  • Open Access Logo Poster (Online Präsentation)
    Summer School Dresden Microelectronics Academy 2021, 20.-24.09.2021, Online, Online


Direct Imaging of Distorted Vortex Structure and Vortex-Antivortex Mediated Vortex Annihilation In Exchange Coupled Ferromagnetic/Antiferromagnetic Disk Structures

S. S. P. K. Arekapudi, B. Böhm, L. Ramasubramanian, F. Ganss, P. Heinig, S. Stienen, C. Fowley, K. Lenz, A. M. Deac, M. Albrecht, O. Hellwig

Topological spin textures such as skyrmions, merons, and vortices in antiferromagnetic (AFM)/ ferromagnetic (FM) materials are actively explored for utilization in future data storage and signal processing devices. An emergent half-integer spin texture such as a magnetic vortex can be stabilized in a soft magnetic NiFe disk structure. Due to the topological nature, the unwinding of the magnetic vortex phase is mediated by the dynamic creation and subsequent annihilation of magnetic singularities, such as Bloch points. This process enables the formation of intermediate topological phases such as vortex-antivortex (V-AV) pairs and edge states. Interfacial interactions between an AFM and a topologically non-trivial spin structure of a FM can stabilize and extend the lifetime of V-AV phases, which are typically considered intrinsic and dynamic are imaged using high-resolution in-field magnetic force microscopy. Additionally, these interactions are used to protect the emerged chirality in an otherwise degenerate chiral spin system, rather than to introduce a preferred chirality.

Keywords: Topological defects; Vortex-Antivortex pairs; Antiferromagnet/Ferromagnet; Chirality in magnetism; High resolution magnetic imaging; Magnetic Vortex

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Inertial spin dynamics in ferromagnets

N. Kumar, N. Awari, S. Kovalev, D. Polly, N. Z. Hagström, S. S. P. K. Arekapudi, A. Semisalova, K. Lenz, B. W. Green, J.-C. Deinert, I. Ilyakov, M. Chen, M. Bawatna, V. Scalera, M. D’Aquino, C. Serpico, O. Hellwig, W. Jean-Eric, M. Gensch, S. Bonetti

The understanding of how spins move at pico- and femtosecond time scales is the goal of much of modern research in condensed matter physics, with implications for ultrafast and more energy-efficient data storage. However, the limited comprehension of the physics behind this phenomenon has hampered the possibility of realising a commercial technology based on it. Recently, it has been suggested that inertial effects should be considered in the full description of the spin dynamics at these ultrafast time scales, but a clear observation of such effects in ferromagnets is still lacking. Here, we report the first direct experimental evidence of inertial spin dynamics in ferromagnetic thin films in the form of a nutation of the magnetisation at a frequency of approximately 0.6 THz. This allows us to evince that the angular momentum relaxation time in ferromagnets is on the order of 10 ps.

Keywords: Magnetisation; ultrafast spin dynamics; ferromagnetic thin films

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Self-stabilizing exchange-mediated spin transport

T. Schneider, D. Hill, A. Kakay, K. Lenz, J. Lindner, J. Faßbender, P. Upadhyaya, Y. Liu, K. Wang, Y. Tserkovnyak, I. N. Krivorotov, I. Barsukov

Long-range spin transport in magnetic systems can be achieved by means of exchange-mediated spin textures with robust topological winding - a phenomenon referred to as spin superfluidity. Its experimental signatures have been discussed in antiferromagnets which are nearly free of dipolar interaction. In ferromagnets, which present with non-negligible dipole fields, however, realization of such spin transport has remained a challenge. Using micromagnetic simulations, we investigate exchange-mediated spin transport in extended thin ferromagnetic films. We uncover a two-fluidstate, in which the long-range spin transport by spin textures co-exists with and is stabilized by spin waves, as well as a soliton-screened spin transport regime at high spin injection biases. Both states are associated with distinct spin texture reconstructions near the spin injection region and sustain spin transport over large distances.

Keywords: Spin waves; superfluidity; bosons; micromagnetism; dipole-dipole interaction; Landau instability

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A. Smith, K. Sobotkiewich, A. Khan, E. A. Montoya, L. Yang, Z. Duan, T. Schneider, K. Lenz, J. Lindner, K. An, X. Li, I. N. Krivorotov
Dimensional crossover in spin Hall oscillators
Phys. Rev. B 102, 054422 (2020)
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T. Huang, V. R. Misko, S. Gobeil, X. Wang, F. Nori, J. Schütt, J. Fassbender, G. Cuniberti, D. Makarov, L. Baraban
Inverse Solidification Induced by Active Janus Particles
Adv. Funct. Mater., 2003851 (2020)
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E. Baek, N. Ranjan Das, C. Vittorio Cannistraci, T. Rim, G. Santiago Cañón Bermúdez, K. Nych, H. Cho, K. Kim, C.-K. Baek, D. Makarov, R. Tetzlaff, L. Chua, L. Baraban, G. Cuniberti
Intrinsic plasticity of silicon nanowire neurotransistors for dynamic memory and learning functions
Nature Electronics 3, 398 (2020)
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T. Hula, K. Schultheiß, A. Buzdakov, L. Körber, M. Bejarano, L. Flacke, L. Liensberger, M. Weiler, J. M. Shaw, H. T. Nembach, J. Faßbender, H. Schultheiß
Nonlinear losses in magnon transport due to four-magnon scattering
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J. Llandro, D. M. Love, A. Kovács, J. Caron, K. N. Vyas, A. Kakay, R. Salikhov, K. Lenz, J. Faßbender, M. R. J. Scherer, C. Cimorra, U. Steiner, C. H. W. Barnes, R. E. Dunin-Borkowski, S. Fukami, H. Ohno
Visualizing Magnetic Structure in 3D Nanoscale Ni–Fe Gyroid Networks
Nano Lett. 20, 3642 (2020)
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S. Pile, M. Buchner, V. Ney, T. Schaffers, K. Lenz, R. Narkovic, J. Lindner, H. Ohldag, A. Ney
Direct imaging of the ac component of the pumped spin polarization with element specificity
Phys. Rev. Appl. 14, 034005 (2020)
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T. Huang, S. Gobeil, X. Wang, V. Misko, F. Nori, W. de Malsche, J. Faßbender, D. Makarov, G. Cuniberti, L. Baraban
Anisotropic exclusion effect between photocatalytic Ag/AgCl Janus particles and passive beads in a dense colloidal matrix
Langmuir 36, 7091 (2020)
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J. Lumetzberger, M. Buchner, S. Pile, V. Ney, W. Gaderbauer, N. Daffé, M. V. Moro, D. Primetzhofer, K. Lenz, A. Ney
Influence of structure and cation distribution on magnetic anisotropy and damping in Zn/Al doped nickel ferrites
Phys. Rev. B 102, 054402 (2020)
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C. Wang, C.-H. Chang, A. Herklotz, C. Chen, F. Ganss, U. Kentsch, D. Chen, X. Gao, Y.-J. Zeng, O. Hellwig, M. Helm, S. Gemming, Y.-H. Chu, S. Zhou
Topological Hall effect in single thick SrRuO3 layers induced by defect engineering
Adv. Electron. Mater. (2020)
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T. Hache, Y. Li, T. Weinhold, B. Scheumann, F. J. Trindade Goncalves, O. Hellwig, J. Faßbender, H. Schultheiß
Bipolar spin Hall nano-oscillators
Appl. Phys. Lett. 116, 192405 (2020)
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B. Eggert, A. Schmeink, J. Lill, M. O. Liedke, U. Kentsch, M. Butterling, A. Wagner, S. Pascarelli, K. Potzger, J. Lindner, T. Thomson, J. Fassbender, K. Ollefs, W. Keune, R. Bali, H. Wende
Magnetic response of FeRh to static and dynamic disorder
RSC Adv. 10, 14386 (2020)
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O. Pylypovskyi, V. P. Kravchuk, O. Volkov, J. Faßbender, D. Sheka, D. Makarov
Unidirectional tilt of domain walls in equilibrium in biaxial stripes with Dzyaloshinskii–Moriya interaction
Appl. Phys. Lett. 53, 395003 (2020)
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L. Ramasubramanian, A. Kákay, C. Fowley, O. Yildirim, P. Matthes, S. Sorokin, A. Titova, D. Hilliard, R. Böttger, R. Hübner, S. Gemming, S. E. Schulz, F. Kronast, D. Makarov, J. Faßbender, A. M. Deac
Tunable magnetic vortex dynamics in ion-implanted permalloy disks
ACS Appl. Mater. Interfaces 12, 27812 (2020)
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O. Yildirim, D. Hilliard, S. S. P. K. Arekapudi, C. Fowley, H. Cansever, L. Koch, L. Ramasubramanian, S. Zhou, R. Böttger, J. Lindner, J. Faßbender, O. Hellwig, A. M. Deac
Ion-irradiation-induced cobalt/cobalt oxide heterostructures: printing 3D interfaces
ACS Appl. Mater. Interfaces 12, 9858 (2020)
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D. D. Sheka, O. Pylypovskyi, P. Landeros, Y. Gaididei, A. Kakay, D. Makarov
Nonlocal chiral symmetry breaking in curvilinear magnetic shells
Communications Physics 3, 128 (2020)
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H. Zhong, M. Ghorbani-Asl, K. H. Ly, J. Ge, J. Zhang, M. Wang, Z. Liao, D. Makarov, E. Zschech, E. Brunner, I. M. Weidinger, J. Zhang, A. Krasheninnikov, S. Kaskel, R. Dong, X. Feng
Synergistic Electroreduction of Carbon Dioxide to Carbon Monoxide on Bimetallic Layered Conjugated Metal-Organic Frameworks
Nat. Commun. 11, 1409 (2020)
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M. Melzer, D. Makarov, O. G. Schmidt
A review on stretchable magnetic field sensorics
J. Phys. D Appl. Phys. 53, 083002 (2020)
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S. Sorokin, R. Gallardo, C. Fowley, K. Lenz, A. Titova, G. Dennehy, G. Atcheson, K. Rode, J. Faßbender, J. Lindner, A. M. Deac
Magnetization dynamics in synthetic antiferromagnets: the role of dynamical energy and mutual spin-pumping
Phys. Rev. B 101, 14410 (2020)
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T. Hache, M. Vaňatka, L. Flajšman, T. Weinhold, T. Hula, O. Ciubotariu, M. Albrecht, B. Arkook, I. Barsukov, L. Fallarino, O. Hellwig, J. Faßbender, M. Urbánek, H. Schultheiß
Freestanding and positionable microwave-antenna device for magneto-optical spectroscopy experiments
Phys. Rev. Appl. 13, 054009 (2020)
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C. Dubs, O. Surzhenko, R. Thomas, J. Osten, T. Schneider, K. Lenz, J. Grenzer, R. Hübner, W. Elke
Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy
Phys. Rev. Mater. 4, 024416 (2020)
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B. Dieny, I. L. Prejbeanu, K. Garello, P. Gambardella, P. Freitas, R. Lehndorff, W. Raberg, U. Ebels, S. O. Demokritov, J. Akerman, A. Deac, P. Pirro, C. Adelmann, A. Anane, A. V. Chumak, A. Hiroata, S. Mangin, M. Cengiz Onbaşlı, M. D’Aquino, G. Prenat, G. Finocchio, L. Lopez Diaz, R. Chantrell, O. Chubykalo-Fesenko, P. Bortolotti
Opportunities and challenges for spintronics in the microelectronic industry
Nature Electronics 3, 446 (2020)
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J. Ehrler, B. Sanyal, J. Grenzer, S. Zhou, R. Böttger, H. Wende, J. Lindner, J. Faßbender, C. Leyens, K. Potzger, R. Bali
Magneto-structural correlations in a systematically disordered B2 lattice
New J. Phys. 22, 073004 (2020)
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Concept of artificial magnetoelectric materials via geometrically controlling curvilinear helimagnets
O. Volkov, U. K. Rößler, J. Faßbender, D. Makarov
J. Phys. D Appl. Phys. 52, 345001 (2019)
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Experimental Observation of Exchange-Driven Chiral Effects in Curvilinear Magnetism
O. Volkov, A. Kakay, K. Florian, J. I. Mönch, M. Mohamad-Assaad, J. Faßbender, D. Makarov
Phys. Rev. Lett. 123, 077201 (2019)
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Thermodynamics and determination of the exchange stiffness of asymmetrically sandwiched ultrathin ferromagnetic films with perpendicular anisotropy
I. Iastremskyi, O. Volkov, M. Kopte, T. Kosub, S. Stienen, K. Lenz, J. Lindner, J. Faßbender, B. A. Ivanov, D. Makarov
Phys. Rev. Appl. 12, 064038 (2019)
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Gilbert damping in NiFeGd compounds: Ferromagnetic resonance versus time-resolved spectroscopy
R. Salikhov, A. Alekhin, T. Parpiiev, T. Pezeril, D. Makarov, R. Abrudan, R. Meckenstock, F. Radu, M. Farle, H. Zabel, V. V. Temnov
Phys. Rev. B 99, 104412 (2019)
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Finite-size effects in ultrafast remagnetization dynamics of FePt
L. Willig, A. von Reppert, M. Deb, F. Ganss, O. Hellwig, M. Bargheer
Phys. Rev. B 100, 224408 (2019)
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Imaging and writing magnetic domains in the non-collinear antiferromagnet Mn₃Sn
H. Reichlova, T. Janda, J. Godinho, A. Markou, D. Kriegner, R. Schlitz, J. Zelezny, Z. Soban, M. Bejarano, H. Schultheiß, P. Nemec, T. Jungwirth, C. Felser, J. Wunderlich, S. Goennenwein
Nat. Commun. 10, 5459 (2019)
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Spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy study of thermally treated Co60Fe20B20 thin films
M. Hoffmann, A. Sharma, P. Matthes, S. Okano, O. Hellwig, R. Ecke, D. Zahn, G. Salvan, S. Schulz
J. Phys.: Condens. Matter 32, 055702 (2019)
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Femtosecond X-ray induced changes of the electronic and magnetic response of solids from electron redistribution
D. Higley, A. Reid, Z. Chen, L. Le Guyader, O. Hellwig, A. Lutman, T. Liu, P. Shafer, T. Chase, G. Dakovski, A. Mitra, E. Yuan, J. Schlappa, H. Dürr, W. Schlotter, J. Stöhr
Nat. Commun. 10, 5289 (2019)
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Antiferromagnetic domain wall control via surface spin flop in fully tunable synthetic antiferromagnets with perpendicular magnetic anisotropy
B. Böhm, L. Fallarino, D. Pohl, B. Rellinghaus, K. Nielsch, N. S. Kiselev, O. Hellwig
Phys. Rev. B 100, 140411 (2019)
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Independent Geometrical Control of Spin and Charge Resistances in Curved Spintronics
K. S. Das, D. Makarov, P. Gentile, M. Cuoco, B. J. van Wees, C. Ortix, I. J. Vera-Marun
Nano Lett. 19, 6839 (2019)
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Strain Anisotropy and Magnetic Domains in Embedded Nanomagnets
M. Nord, A. Semisalova, A. Kákay, G. Hlawacek, I. Maclaren, V. Liersch, O. Volkov, D. Makarov, G. W. Paterson, K. Potzger, J. Lindner, J. Faßbender, D. Mcgrouther, R. Bali
Small 15, 1904738 (2019)
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Implantable highly compliant devices for heating of internal organs: towards cancer treatment
G. S. Cañón Bermudez, A. Kruv, T. Voitsekhivska, I. Hochnadel, A. Lebanov, A. Potthoff, J. Fassbender, T. Yevsa, D. Makarov
Adv. Eng. Mater. 21, 1900407 (2019)
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A bimodal soft electronic skin for tactile and touchless interaction in real time
J. Ge, X. Wang, M. Drack, O. Volkov, M. Liang, G. S. Cañón Bermúdez, R. Illing, C. Wang, S. Zhou, J. Fassbender, M. Kaltenbrunner, D. Makarov
Nat. Commun. 10, 4405 (2019)
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Spin Hall magnetoresistance in heterostructures consisting of noncrystalline paramagnetic YIG and Pt
M. Lammel, R. Schlitz, K. Geishendorf, D. Makarov, T. Kosub, S. Fabretti, H. Reichlova, R. Huebner, K. Nielsch, A. Thomas, S. T. B. Goennenwein
Appl. Phys. Lett. 114, 252402 (2019)
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Magnetization Dynamics of an Individual Single-Crystalline Fe-Filled Carbon Nanotube
K. Lenz, R. Narkowicz, K. Wagner, C. F. Reiche, J. Körner, T. Schneider, A. Kákay, H. Schultheiss, D. Suter, B. Büchner, J. Fassbender, T. Mühl, J. Lindner
Small 15, 1904315 (2019)
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Strain-induced perpendicular magnetic anisotropy and Gilbert damping of Tm3Fe5O12 thin films
O. Ciubotariu, A. Semisalova, K. Lenz, M. Albrecht
Sci Rep 9, 17474 (2019)
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Synthesis of Mg and Zn diolates and their use in metal oxide deposition
P. Frenzel, A. Preuß, J. Bankwitz, C. Georgi, F. Ganss, L. Mertens, S. Schulz, O. Hellwig, M. Mehring, H. Lang
RSC Adv. 9, 10657 (2019)
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High spin-wave propagation length consistent with low damping in a metallic ferromagnet
L. Flacke, L. Liensberger, M. Althammer, H. Huebl, S. Geprägs, K. Schultheiß, A. Buzdakov, T. Hula, H. Schultheiß, E. R. J. Edwards, H. T. Nembach, J. M. Shaw, R. Gross, M. Weiler
Appl. Phys. Lett. 115, 122402 (2019)
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Nonlinear ferromagnetic resonance in the presence of 3-magnon scattering in magnetic nanostructures
D. V. Slobodianiuk, G. A. Melkov, K. Schultheiß, H. Schultheiß, R. V. Verba
IEEE Magn. Lett. 10, 6103405 (2019)
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Nanomagnetism of Magnetoelectric Granular Thin-Film Antiferromagnets
P. Appel, B. J. Shields, T. Kosub, N. Hedrich, R. Hübner, J. Fassbender, D. Makarov, P. Maletinsky
Nano Lett. 19, 1682 (2019)
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Zero-field dynamics stabilized by in-plane shape anisotropy in MgO-based spin-torque oscillators
E. Kowalska, A. Kákay, C. Fowley, V. Sluka, J. Lindner, J. Fassbender, A. M. Deac
J. Appl. Phys. 125, 083902 (2019)
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Effect of insertion layer on electrode properties in magnetic tunnel junctions with a zero-moment half-metal
A. Titova, C. Fowley, E. Clifford, Y.-C. Lau, K. Borisov, D. Betto, G. Atcheson, R. Hübner, C. Xu, P. Stamenov, M. Coey, K. Rode, J. Lindner, J. Fassbender, A. M. Deac
Sci Rep 9, 4020 (2019)
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Characterization of Continuous Wave Laser-Induced Thermal Gradients in Magnetic Tunnel Junctions Integrated Into Microresonators via COMSOL Simulations
H. Cansever, J. Lindner, T. Huebner, A. Niesen, G. Reiss, J. Faßbender, A. M. Deac
IEEE T. Magn. 55 (2019)
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Tuning Ferromagnetic Resonance via Disorder/Order Interfaces
T. Schneider, K. Lenz, A. Semisalova, J. Gollwitzer, J. Heitler-Klevans, K. Potzger, J. Fassbender, J. Lindner, R. Bali
J. Appl. Phys. 125, 195302 (2019)
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Reconfigurable spin-wave non-reciprocity induced by dipolar interaction in a coupled ferromagnetic bilayer
R. A. Gallardo, T. Schneider, A. K. Chaurasiya, A. Oelschlägel, S. S. P. K. Arekapudi, A. Roldáan-Molina, R. Hübner, K. Lenz, A. Barman, J. Fassbender, J. Lindner, O. Hellwig, P. Landeros
Phys. Rev. Appl. 12, 034012 (2019)
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Ion induced ferromagnetism combined with self-assembly for large area magnetic modulation of thin films
M. Krupinski, R. Bali, D. Mitin, P. Sobieszczyk, J. Gregor-Pawlowski, A. Zarzycki, R. Böttger, M. Albrecht, K. Potzger, M. Marszałek
Nanoscale 11, 8930 (2019)
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Combined frequency and time domain measurements on injection-locked, constriction-based spin Hall nano-oscillators
T. Hache, T. Weinhold, K. Schultheiss, J. Stigloher, F. Vilsmeier, C. Back, S. S. P. K. Arekapudi, O. Hellwig, J. Fassbender, H. Schultheiss
Appl. Phys. Lett. 114, 102403 (2019)
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Domain wall-based spin-Hall nano-oscillators
N. Sato, K. Schultheiß, L. Körber, N. Puwenberg, T. Mühl, A. A. Awad, S. S. P. K. Arekapudi, O. Hellwig, J. Faßbender, H. Schultheiß
Phys. Rev. Lett. 123, 057204 (2019)
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Excitation of whispering gallery magnons in a magnetic vortex
K. Schultheiss, R. Verba, F. Wehrmann, K. Wagner, L. Körber, T. Hula, T. Hache, A. Kákay, A. A. Awad, V. Tiberkevich, A. N. Slavin, J. Fassbender, H. Schultheiss
Phys. Rev. Lett. 122, 097202 (2019)
DOI: 10.1103/PhysRevLett.122.097202

The role of open-volume defects in the annihilation of antisites in a B2-ordered alloy
J. Ehrler, M. O. Liedke, J. Cizek, R. Boucher, M. Butterling, S. Zhou, R. Böttger, E. Hirschmann, T. T. Trinh, A. Wagner, J. Lindner, J. Fassbender, C. Leyens, K. Potzger, R. Bali
Acta Mater. 176, 167 (2019)
DOI: 10.1016/j.actamat.2019.06.037

Highly compliant planar Hall effect sensor with sub 200 nT sensitivity
P. Granell, G. Wang, G. S. Canon Bermudez, T. Kosub, F. Golmar, L. Steren, J. Fassbender, D. Makarov
npj Flexible electronics 3, 3 (2019)
DOI: 10.1038/s41528-018-0046-9

Experimental and Theoretical Study of Curvature Effects in Parabolic Nanostripes
O. M. Volkov, F. Kronast, I. Mönch, M.-A. Mawass, A. Kákay, J. Fassbender, D. Makarov
Phys. Status Solidi 13, 1800309 (2019)
DOI: 10.1002/pssr.201800309

Spin-wave nonreciprocity on magnetization-graded ferromagnetic films
R. A. Gallardo, P. Alvarado-Seguel, T. Schneider, C. Gonzalez-Fuentes, A. Roldán-Molina, K. Lenz, J. Lindner, P. Landeros
New J. Phys. 21, 033026 (2019)
DOI: 10.1088/1367-2630/ab0449

Structure-property relationship of Co2MnSi thin films in response to He+-irradiation
F. Hammerath, R. Bali, R. Hübner, M. R. D. Brandt, S. Rodan, K. Potzger, R. Böttger, Y. Sakuraba, B. Büchner, S. Wurmehl
Sci Rep 9, 2766 (2019)
DOI: 10.1038/s41598-019-39435-4

Tunnel magnetoresistance angular and bias dependence enabling tuneable wireless communication
E. Kowalska, A. Fukushima, V. Sluka, C. Fowley, A. Kákay, Y. Aleksandrov, J. Lindner, J. Fassbender, S. Yuasa, A. M. Deac
Sci Rep 9, 9541 (2019)
DOI: 10.1038/s41598-019-45984-5

Emission and Propagation of Multi-Dimensional Spin Waves in Anisotropic Spin Textures
V. Sluka, T. Schneider, R. A. Gallardo, A. Kakay, M. Weigand, T. Warnatz, R. Mattheis, A. Roldan-Molina, P. Landeros, V. Tiberkevich, A. Slavin, G. Schütz, A. Erbe, A. Deac, J. Lindner, J. Fassbender, J. Raabe, S. Wintz
Nat. Nanotechnol. 14, 328 (2019)
DOI: 10.1038/s41565-019-0383-4

Flat Bands, Indirect Gaps, and Unconventional Spin-Wave Behavior Induced by a Periodic Dzyaloshinskii-Moriya Interaction
R. A. Gallardo, D. Cortés-Ortuno, T. Schneider, A. Roldán-Molina, F. Ma, K. Lenz, H. Fangohr, J. Lindner, P. Landeros
Phys. Rev. Lett. 122, 067204 (2019)
DOI: 10.1103/PhysRevLett.122.067204

Spin-Wave Modes in Transition from a Thin Film to a Full Magnonic Crystal
M. Langer, R. A. Gallardo, T. Schneider, S. Stienen, A. Roldán-Molina, Y. Yuan, K. Lenz, J. Lindner, P. Landeros, J. Fassbender
Phys. Rev. B 99, 024426 (2019)

Control of domain structure and magnetization reversal in thick Co/Pt multilayers
L. Fallarino, A. Oelschlägel, J. A. Arregi, A. Bashkatov, F. Samad, B. Böhm, K. Chesnel, O. Hellwig
Phys. Rev. B 99, 024431 (2019)

Dynamic Imaging of the Delay-and Tilt-Free Motion of Neel Domain Walls in Perpendicularly Magnetized Superlattices
S. Finizio, S. Wintz, K. Zeissler, A. V. Sadovnikov, S. Mayr, S. A. Nikitov, C. H. Marrows, J. Raabe
Nano Lett. 19, 375 (2019)


270. Hydrogen storage in Mg2FeSi alloy thin films depending on the Fe-to-Si ratio measured by conversion electron Mössbauer spectroscopy
T. T. Trinh, K. Asano, R. Heller, H. Reuther, J. Grenzer, H. Schreuders, B. Dam, K. Potzger
Nucl. Instrum. Meth. B 434, 109 (2018)

269.Chiral Skyrmion and Skyrmionium States Engineered by the Gradient of Curvature
O. V. Pylypovskyi, D. Makarov, V. P. Kravchuk, Y. Gaididei, A. Saxena, D. D. Sheka
Phys. Rev. Appl. 10, 064057 (2018)

268. Controlled coexcitation of direct and indirect ultrafast demagnetization in Co/Pd multilayers with large perpendicular magnetic anisotropy
S. Pan, O. Hellwig, A. Barman
Phys. Rev. B 98, 214436 (2018)

267. Anomalous Hall-like transverse magnetoresistance in Au thin films on Y3Fe5O12
T. Kosub, S. Velez, J. M. Gomez-Perez, L. E. Hueso, J. Fassbender, F. Casanova, D. Makarov
Appl. Phys. Lett. 113, 222409 (2018)

266. Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics
G. S. Cañón Bermúdez, H. Fuchs, L. Bischoff, J. Fassbender, D. Makarov
Nature Electronics 1, 589 (2018)

265. Beyond a phenomenological description of magnetostriction
A. H. Reid, X. Shen, P. Maldonado, T. Chase, E. Jal, P. W. Granitzka, K. Carva, R. K. Li, J. Li, L. Wu, T. Vecchione, T. Liu, Z. Chen, D. J. Higley, N. Hartmann, R. Coffee, J. Wu, G. L. Dakovski, W. F. Schlotter, H. Ohldag, Y. K. Takahashi, V. Mehta, O. Hellwig, A. Fry, Y. Zhu, J. Cao, E. E. Fullerton, J. Stöhr, P. M. Oppeneer, X. J. Wang, H. A. Dürr
Nat. Commun. 9, 388 (2018)

264. Measuring the thermal properties of anisotropic materials using beam-offset frequency domain thermoreflectance
M. Rahman, M. Shahzadeh, P. Braeuninger-Weimer, S. Hofmann, O. Hellwig, S. Pisana
J. Appl. Phys. 123, 245110 (2018)

263. High-frequency measurements of thermophysical properties of thin films using a modified broad-band frequency domain thermoreflectance approach
M. Shahzadeh, M. Rahman, O. Hellwig, S. Pisana
Rev. Sci. Instrum. 89, 084905 (2018)

262. Ultrafast laser generated strain in granular and continuous FePt thin films
A. von Reppert, L. Willig, J.-E. Pudell, M. Rössle, W. Leitenberger, M. Herzog, F. Ganss, O. Hellwig, M. Bargheer
Appl. Phys. Lett. 113, 123101 (2018)

261. Ultrafast Self-Induced X-Ray Transparency and Loss of Magnetic Diffraction
Z. Chen, D. J. Higley, M. Beye, M. Hantschmann, V. Mehta, O. Hellwig, A. Mitra, S. Bonetti, M. Bucher, S. Carron, T. Chase, E. Jal, R. Kukreja, T. Liu, A. H. Reid, G. L. Dakovski, A. Föhlisch, W. F. Schlotter, H. A. Dürr, J. Stöhr
Phys. Rev. Lett. 121, 137403 (2018)

260. Visible Light Actuated Efficient Exclusion Between Plasmonic Ag/AgCl Micromotors and Passive Beads
X. Wang, L. Baraban, V. R. Misko, F. Nori, T. Huang, G. Cuniberti, J. Fassbender, D. Makarov
Small 14, 1802537 (2018)

259. High-Motility Visible Light-Driven Ag/AgCl Janus Micromotors
X. Wang, L. Baraban, A. Nguyen, J. Ge, V. R. Misko, J. Tempere, F. Nori, P. Formanek, T. Huang, G. Cuniberti, J. Fassbender, D. Makarov
Small, 1803613 (2018)

258. Injection locking of multiple auto-oscillation modes in a tapered nanowire spin Hall oscillator
K. Wagner, A. Smith, T. Hache, J.-R. Chen, L. Yang, E. Montoya, K. Schultheiss, J. Lindner, J. Fassbender, I. Krivorotov, H. Schultheiss
Sci Rep 8, 16040 (2018)

257. Geometry-induced motion of magnetic domain walls in curved nanostripes
K. V. Yershov, V. P. Kravchuk, D. D. Sheka, O. V. Pylypovskyi, D. Makarov, Y. Gaididei
Physical Review B 98, 060409 (2018)

256. Localization of magnon modes in a curved magnetic nanowire
Y. Gaididei, V. P. Kravchuk, F. G. Mertens, O. V. Pylypovskyi, A. Saxena, D. D. Sheka, O. M. Volkov
Low Temperature Physics 44, 814 (2018)

255. Frequency linewidth and decay length of spin waves in curved magnetic membranes
J. A. Otalora, A. Kákay, J. Lindner, H. Schultheiss, A. Thomas, J. Fassbender, K. Nielsch
Physical Review B 98, 014403 (2018)

254. Local probe of irradiation induced structural changes and orbital magnetism in Fe60Al40 thin films via order-disorder phase transition
E. La Torre, A. Smekhova, C. Schmitz-Antoniak, K. Ollefs, B. Eggert, B. Cöster, D. Walecki, F. Wilhelm, A. Rogalev, J. Lindner, R. Bali, R. Banerjee, B. Sanyal, H. Wende
Physical Review B 98, 024101 (2018)

253. Investigating spin-transfer torques induced by thermal gradients in magnetic tunnel junctions by using micro-cavity ferromagnetic resonance
H. Cansever, R. Narkowicz, K. Lenz, C. Fowley, L. Ramasubramanian, O. Yildirim, A. Niesen, T. Huebner, G. Reiss, J. Lindner, J. Fassbender, A. M. Deac
Journal of Physics D: Applied Physics 51, 224009 (2018)

252. Unexpected field-induced dynamics in magnetostrictive microstructured elements under isotropic strain
S. Finizio, S. Wintz, S. Gliga, E. Kirk, A. K. Suszka, P. Wohlhüter, K. Zeissler, J. Raabe
Journal of Physics: Condensed Matter 30, 314001 (2018)

251. Origin and Manipulation of Stable Vortex Ground States in Permalloy Nanotubes
M. Zimmermann, T. N. Gerhard-Meier, F. Dirnberger, A. Kákay, M. Decker, S. Wintz, S. Finizio, E. Josten, J. Raabe, M. Kronseder, D. Bougeard, J. Lindner, C. H. Back
Nano Letters 18, 2828 (2018)

250. Laser-Rewriteable Ferromagnetism at Thin Film Surfaces
J. Ehrler, M. He, M. V. Shugaev, N. I. Polushkin, S. Wintz, V. Liersch, S. Cornelius, R. Hübner, K. Potzger, J. Lindner, J. Fassbender, A. A. Ünal, S. Valencia, F. Kronast, L. V. Zhigilei, R. Bali
ACS Applied Materials and Interfaces 10, 15232 (2018)

249. Thick Permalloy films for the imaging of spin texture dynamics in perpendicularly magnetized systems
S. Finizio, S. Wintz, D. Bracher, E. Kirk, A. S. Semisalova, J. Förster, K. Zeissler, T. Weßels, M. Weigand, K. Lenz, A. Kleibert, J. Raabe
Physical Review B 98, 104415 (2018)

248. Multiplet of skyrmion states on a curvilinear defect: Reconfigurable skyrmion lattices
V. P. Kravchuk, D. D. Sheka, A. Kákay, O. M. Volkov, U. K. Rößler, J. van den Brink, D. Makarov, Y. Gaididei
Physical Review Letters 120, 067201 (2018)

247. Symmetries and localization properties of defect modes in metamaterial magnonic superlattices
R. A. Gallardo, T. Schneider, A. Roldán-Molina, M. Langer, A. S. Núñez, K. Lenz, J. Lindner, P. Landeros
Physical Review B 97, 174404 (2018)

246. Magnetosensitive e-skins with directional perception for augmented reality
G. S. Cañón Bermúdez, D. D. Karnaushenko, D. Karnaushenko, A. Lebanov, L. Bischoff, M. Kaltenbrunner, J. Fassbender, O. G. Schmidt, D. Makarov
Science Advances 4, eaao2623 (2018)

245. Mesoscale Dzyaloshinskii-Moriya interaction: geometrical tailoring of the magnetochirality
O. M. Volkov, D. D. Sheka, V. P. Kravchuk, Y. Gaididei, U. K. Rößler, J. Faßbender, D. Makarov
Scientific Reports 8, 866 (2018)

244. Dipolar interaction induced band gaps and flat modes in surface-modulated magnonic crystals
R. A. Gallardo, T. Schneider, A. Roldan-Molina, M. Langer, J. Fassbender, K. Lenz, J. Lindner, P. Landeros
Physical Review B 97, 144405 (2018)

243. Positron Annihilation Studies using a Superconducting Electron LINAC
A. Wagner, M. Butterling, E. Hirschmann, R. Krause-Rehberg, M. O. Liedke, K. Potzger
AIP Conference Proceedings 1970, 040003 (2018)

242. Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties
Q. Jia, X. Ou, M. Langer, B. Schreiber, J. Grenzer, P. F. Siles, R. D. Rodriguez, K. Huang, Y. Yuan, A. Heidarian, R. Hübner, T. You, W. Yu, K. Lenz, J. Lindner, X. Wang, S. Facsko
Nano Research 11, 3519 (2018)

241. Interplay between magnetic domain patterning and anisotropic magnetoresistance probed by magnetooptics
J. Osten, K. Lenz, H. Schultheiss, J. Lindner, J. McCord, J. Fassbender
Physical Review B 97, 014415 (2018)

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