Unprecedented magnetoelectric functionality in nanoscale ferromagnetic metal films has been discovered in recent, gated architectures. Two likely mechanisms are being considered: (I) capacitive electronic charging effects and (II) voltage-triggered ionic chemical changes at the magnetic interface. One key aspect of the latter is that the magnetic states created by redox reactions can persist after the voltage has been switched off, enabling voltage-programmable magnetic materials.
We demonstrate reversible voltage-induced changes in coercivity (up to 80% change), saturation magnetization (up to 64% change), and magnetic domain structure in sputtered Fe films gated via alkaline electrolytes.[1,2] These large magnetic changes are achieved within seconds at room temperature and with the application of a low voltage of just a few volts. This is feasible due to the liquid electrolytes which enable larger electric fields and higher ionic mobility at the interface in comparison to solid dielectric layers. The magnetic changes during polarization are detected via in-situ transport measurements, in-situ ferromagnetic resonance, and in-situ Kerr microscopy. The underlying mechanisms, namely reduction/oxidation reactions involving the native oxide layer, are revealed by electrochemical analysis and surface sensitive analytic techniques. Current results showing the extension of ionic control mechanisms towards magnetic heterostructures at critical points and to electrodeposited nanoislands will be presented.[2-4]
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 K. Duschek et al., J. Mater. Chem. C 6, 8411 (2018)