Voltage-control of magnetism in metal/metal oxide thin films by electrochemical approaches and interface design

Synopsis

Reversible control of magnetism by an electric field is of key interest for the miniaturization of magnetic systems like sensors or actuators, magnetic data storage, as well as for novel spintronic devices. In comparison to magnetic semiconductors and multiferroic materials, electric field effects in ultrathin metal layers have recently gained a lot of attention due to the combination of large magnetization and room-temperature applicability [1].

We could demonstrate large voltage-induced changes of saturation magnetization, coercivity and magnetic anisotropy in ultrathin Fe, FePt, CoPt and FePt/Fe films polarized in an electrolyte. The effects are based on reversible electrochemical reactions transforming the transition metal into its oxides and vice versa. Large changes are achieved for very thin films and at critical points as, e.g., the transition from in-plane to perpendicular anisotropy or the transition from the rigid magnet to the exchange spring magnet regime [2,3].
We use in situ anomalous Hall effect (AHE) and in situ ferromagnetic resonance (FMR) measurements to probe the magnetic changes during polarization in an electrolyte. An in situ Kerr microscope is currently being set up to allow for in situ domain observation.

[1] U. Bauer et al., Nature Mater. 14 (2015) 174
[2] K. Leistner et al., Phys. Rev. B 87 (2013) 224411
[3] K. Duschek et al., Appl. Phys. Lett. Mater. 4 (2016) 032301