Large Reversible Voltage Manipulation of Interfacial Magnetic Anisotropy in Pt/Co/Oxide Multilayers

Abstract

The voltage control of magnetic anisotropy (VCMA) is an active field of research, as it is a promising route towards the realization of low power spintronic devices. Among a few proposed VCMA mechanisms, voltage-induced oxygen migration (i.e., magneto-ionic effect) has demonstrated large modulation of magnetic anisotropy.In this work, we study the voltage control of the interfacial perpendicular magnetic anisotropy (PMA) in a series of Pt/Co/MOx (M=Al and Tb) trilayers [1]. The stacks were patterned by electron beam lithography and ion beam etching into stripes (1 – 50 µm width) then covered with a 10 nm thick ZrO2 dielectric layer and a 6 nm thick Pt top electrode to form capacitor-like structures.We show a large modification of interfacial magnetic anisotropy (β>2000fJ(Vm)) accompanied by a non-volatile effect at room temperature (RT). This modification is explained in terms of voltage-induced oxygen migration towards/away from the Co/MOx interface. The Co films can be reversibly switched from an under-oxidized state with in-plane anisotropy (IPA) to an optimal oxidized state with maximum PMA, to an over-oxidized state under applied voltage (see figure). The switching time depends on the amplitude of the applied voltage. Here, we demonstrate that the switching time can be reduced from several seconds down to few milliseconds at RT by adjusting the voltage amplitude. **