Ionic control of magnetism in all-solid-state CoOx/yttria-stabilized zirconia heterostructures

Magneto-ionic gating, a procedure that enables the modulation of materials' magnetic properties by voltage-driven ion motion, offers alternative perspectives for emerging low-power magnetic storage and spintronic applications. Most previous studies in all-solid-state magneto-ionic systems have focused on the control of interfacial magnetism of ultrathin (i.e., 1-3 nm) magnetic films, taking advantage of an adjacent ionic conducting oxide, usually GdO or HfO, that transports functional ionic species (e.g., H or O). Here, we report on room-temperature OFF-ON ferromagnetism by solid-state magneto-ionics in relatively thick (25 nm) patterned CoO films grown on an yttria-stabilized zirconia (YSZ) layer, which acts as a dielectric to hold electric field and as an O ion reservoir. Upon negatively biasing, O ions from the CoO tend to migrate toward the YSZ gate electrode, leading to the gradual generation of magnetization (i.e., OFF-to-ON switching of a ferromagnetic state). X-ray absorption and magnetic circular dichroism studies reveal subtle changes in the electronic/chemical characteristics, responsible for the induced magnetoelectric effects in such all-oxide heterostructures. Recovery of the initial (virtually non-magnetic) state is achieved by application of a positive voltage. The study may guide future development of all-solid-state low-power CMOS-compatible magneto-ionic devices.