Voltage-Driven All-Solid-State Ionic Control on Co/CoO Antiferromagnet/Ferromagnet Exchange Bias.

Spintronics traditionally relies on a large electric current to create magnetic fields or spin torques to manipulate magnetic properties, which inevitably leads to undesirable energy dissipation. Alternatively, the voltage control of magnetism (VCM) promises significantly lower energy costs. In the context of VCM, magneto-ionics distinguishes itself by leveraging voltage-driven ion transport as an energy-efficient approach to control magnetic properties, including magnetization, coercive field, and exchange bias (EB). Herein, we demonstrate that the voltage-driven ionic control of CoO antiferromagnetism allows manipulation of the magnetic properties in exchange-coupled ferromagnetic Co. In a "battery-like" device geometry, a 5 nm Co film is precisely oxidized to realize the Co/CoO heterostructure that is interfaced with a solid-state electrolyte and an anode-like Li ion source. The cathode-like CoO layer reversibly converts back and forth between Co and CoO under gate biases, even after 1000 cycles. This subsequently influences magnetic switching in the exchange-coupled Co layer, which is directly revealed by anisotropic magnetoresistance (AMR) in the Co channel. Our findings demonstrate an efficient method of all-solid-state, voltage-driven, highly reversible ionic control on magnetic channels, offering additional dimensions of control and mass integration capability for spintronic applications.