Research and Projects on Spintronics
Helmholtz Young Investigator Group Dr. Alina Deac
A spin-polarized current flowing through a ferromagnet exerts a torque on the magnetization at the nanoscale, thereby providing means of manipulating it. In a nano-size magnet, spin-transfer torques can induce either magnetization reversal or steady-state precession. These phenomena have been proposed as write method for non-volatile magnetic memory devices and operating mechanism for tuneable radio-frequency nano-oscillators, respectively. Given their good scaling perspectives, spin-torque devices have recently been identified as one of the prime candidates for beyond Moore technologies. In particular, spin-torque devices based on MgO-based magnetic tunnel junctions show great promise for applications, although fundamental questions remain to be answered. Our research aims at unlocking the full potential of these devices with respect to Information-Communication Technology (ICT) by addressing critical outstanding challenges in understanding the fundamental physics of spin-transfer, and providing proof of concept for previously unexplored device structures and fabrication methods.
We focus on three key objectives:
- Establishing a unified understanding of spin-torque induced magnetization reversal, and identifying structures which combine thermal stability compatible with storage applications, reliably controlled writing and sufficiently low writing currents;
- Creating tunable, zero-field spin-torque oscillators capable of simultaneously sustaining large output power (~µW) and narrow linewidth (~MHz), with a view on pushing their operation frequency towards higher ranges;
- Developing the foundational science necessary to understand the potential of spin-transfer torques induced by thermal gradients to be functionalized for reducing power consumption, either on their own or in conjunction with spin polarized currents.
To achieve these objectives, new geometries are developed together with highly engineered structures using novel materials with both in-plane and perpendicular magnetic anisotropies, in collaboration with leading research groups around the world. Novel proton-irradiation techniques for locally modifying the conductive properties of oxides at the nanometer scale are explored, thereby allowing for the study of arrays of devices with densities inaccessible by state-of-the-art patterning methods.
- Giant and Tunnel Magnetoresistance with half-metallic electrodes
- Spin-transfer induced switching in MgO-based magnetic tunnel junctions
- Spin-torque bias dependence in MgO-based magnetic tunnel junctions
- Perpendicular magnetic anisotropy in ultrathin CoFeB layers
- Materials with ultra-high perpendicular anisotropy
- Current-driven dynamics in hybrid geometry magnetic tunnel junctions
- Novel patterning of spin-torque-nano-oscillators using ion beams
- Thermal Spin Transfer Torque
- Vortex dynamics in disks with tailored magnetisations
Dr. Alina Maria Deac (Group Leader)
Ewa Kowalska (PhD Student)
Hamza Cansever (PhD Student)
Aleksandra Titova (PhD Student)
Serhii Sorokin (PhD Student)
Lakshmi Ramasubramanian (Master Student)
Donovan Hilliard (ShK)
Dr. Katarzyna Wiesenhütter (Outreach and Dissemination Manager)
Dr. Oguz Yildirim (Postdoc)
Dr. Ciaran Fowley (Postdoc)
Jingyu Duan (Master student)
Yuriy Aleksandrov (PhD Student)
Hande Isim (ShK)
Nicholas Carton (Internship Student)
Eugene Clifford (Internship Student)
Tiago Cordeiro (HZDR International Summer Student program member)
Dr. David Ball (Postdoc)
Dr. Volker Sluka (Postdoc)
Dongseok Kim (Visiting PhD student of Prof. Kungwon Rhie)
Prof. Kungwon Rhie (Guest Researcher)
Dipl.-Ing. Kerstin Bernert (PhD student)
Julia Gritsenko (HZDR International Summer Student program member)
Dr. Huadong Gan (Guest Researcher)
Wen Feng (HZDR International Summer Student program member, Masters Student)
Sylvain Mathonnière (HZDR International Summer Student program member, Masters Student)
Alexane Pointillon (Masters Student)
If you are interested in joining our group for your Bachelor, Masters or Diploma internship, or as a student lab assistent, please contact Dr. Alina Deac (firstname.lastname@example.org).
- Prof. Michael Farle, University Duisburg-Essen (Campus Duisburg, Germany)
- Prof. Claudia Felser, Max Planck Institute for Chemical Physics of Solids (Dresden, Germany)
- Assoc. Prof. Erol Girt, Simon Fraser University (Vancouver, Canada)
- Dr. Riccardo Hertel, Institut de Physique et Chimie des Matériaux de Strasbourg (Strasbourg, France)
- Prof. Stéphane Mangin, Nancy-Université (Nancy, France)
- Dr. Berthold Ocker, Singulus Technologies AG (Kahl am Main, Germany)
- Dr. William Rippard, The National Institute of Standards and Technology (Boulder, USA)
- Prof. Claus Schneider, Forschungszentrum Jülich (Jülich, Germany)
- Prof. Thomas Thomson, The University of Manchester (Manchester, United Kingdom)
- Dr. Shinji Yuasa, National Institute of Advanced Industrial Science and Technology (Tsukuba, Japan)
"Large Emission Power over 2 µW with High Q Factor Obtained from Nanocontact Magnetic-Tunnel-Junction-Based Spin Torque Oscillator", Maehara, H., Kubota, H., Seki, S., Nishimura, K., Nagamine, Y., Tsunekawa, K., Fukushima, A., Deac, A.M., Ando, K., and Yuasa, S., Appl. Phys. Express 6, 113005 (2013).
URL: http://iopscience.iop.org/1882-0786/6/11/113005/pdf/1882-0786_6_11_113005.pdf DOI:10.7567/APEX.6.113005
"Local modification of magnetic anisotropy and ion milling of Co/Pt multilayers using a He+ ion beam microscope", Fowley, C.,Diao, Z, Faulkner, C.C., Kally, J., Ackland, K., Behan, G., Zhang, H. Z., Deac, A.M., Coey, J.M.D., J. Phys. D: Appl. Phys. 46, 195501 (2013).
URL: http://iopscience.iop.org/0022-3727/46/19/195501/ DOI:10.1088/0022-3727/46/19/195501
"Spin-transfer dynamics in spin valves with out-of-plane magnetized CoNi free layers", Rippard, W.H., Deac, A.M., Pufall, M.R., Shaw, J.M., Keller, M.W., Russek, S.E., Bauer, G.E.W., Serpico, C., Physical Review B - Condensed Matter and Materials Physics 81, 014426 (2010).
URL: http://link.aps.org/doi/10.1103/PhysRevB.81.014426 DOI:10.1103/PhysRevB.81.014426
"Bias-driven high-power microwave emission from MgO-based tunnel magnetoresistance devices", Deac, A.M., Fukushima, A., Kubota, H., Maehara, H., Suzuki, Y., Yuasa, S., Nagamine, Y., Tsunekawa, K., Djayaprawira, D.D., Watanabe, N., Nature Physics 4, 803 - 809 (2008).
URL: http://www.nature.com/nphys/journal/v4/n10/abs/nphys1036.html DOI:10.1038/nphys1036