Voltage Gated Toggling of Exchange Bias in GdCo/NiO Thin Film Heterostructures*

Electrical control of exchange bias (EB) in a antiferromagnet/ferro(ferri)magnet heterostructure is highly desirable for spintronic applications, but is very hard to achieve since the effect is related to the spin order in both the antiferromagnet and the ferro(ferri)magnet, which electric fields have little influence over. Recently, It has been shown that ferrimagnetic order in GdCo thin films can be dynamically controlled by voltage through solid-state hydrogen gating [1], via modulation of the relative magnetic moments of the two sublattices that make up GdCo. Here we show that, when a GdCo/NiO bilayer with out of plane magnetization is loaded/unloaded with hydrogen, the expected switching of the dominant sublattice in GdCo is accompanied by a flipping of the effective EB direction as well. We demonstrate cyclical toggling of EB in heterostructures with fully shifted hysteresis loops by application of only modest voltages (<2V). Our robust but simple mechanism provides a powerful means of controlling EB that can have broad implications for spintronics.
[1]. M. Huang et al., manuscript under review