Voltage-programmable magnetism in metal oxide/metal thin films and nanoislands by electrolytic gating
Dr.-Ing. Karin Leistner
Institut für Metallische Werkstoffe Leibniz-Institut für Festkörper- und Werkstoffforschung, Dresden
17:15 - 18:15 Tuesday 13 November 2018 TUG P2 Voltage control of magnetism is a vibrant field of research that is continuously triggered by interesting physical phenomena and the enormous potential for energy-efficient nanoscale device application. Lately, unprecedented magnetoelectric phenomena in nanoscale ferromagnetic metals have been discovered in gated architectures. Two main mechanism are currently distinguished: (I) capacitive electronic charging effects and (II) voltage-triggered ionic mechanisms and related chemical changes at the magnetic interface. One key aspect of the latter is that the magnetic states set by redox reactions can persist after the voltage has been switched off, enabling voltage-programmable magnetic materials.
The talk will first focus on voltage-induced changes in magnetic anisotropy, coercivity and saturation magnetization that are achieved in ultrathin FePt, CoPt and Fe films gated via liquid electrolytes.[1,2] In order to detect the magnetic changes during voltage application in the electrolyte in situ measurement methods such as in situ transport, in situ ferromagnetic resonance, and in situ Kerr microscopy are utilized. The underlying mechanisms, namely reduction/oxidation reactions involving the native oxide layer, are revealed by electrochemical analysis and surface sensitive analytic techniques. Since in the liquid electrolyte the electric field and the ionic mobility are enhanced in comparison to solid dielectric layers, large magnetic changes are achieved at room temperature and with the application of merely few volts. The talk will further present current works regarding the extension of ionic control mechanisms towards magnetic heterostructures at critical points (spin reorientation, exchange bias) and to nanoislands.[2-4]
[1] K. Leistner, J. Wunderwald, N. Lange, S. Oswald, M. Richter, H. Zhang, L. Schultz and S. Fähler,
Phys. Rev. B 87, 224411 (2013)
[2] K. Duschek, D. Pohl, S. Fähler, K. Nielsch, and K. Leistner, APL Mater. 4, 03231 (2016)
[3] K. Leistner, M. Yang, C. Damm, S. Oswald, A. Petr, V. Kataev, K. Nielsch, and K.L. Kavanagh, Nanoscale 9, 5315 (2017).
[4] K. Duschek, A. Petr, J. Zehner, K. Nielsch, and K. Leistner, J. Mater. Chem. C 6, 8411 (2018)
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