Reversible Control of Magnetic Anisotropy and Magnetization in Amorphous Co40Fe40B20 Thin Films via All-Solid-State Li-ion Redox Capacitor

The emerging field of ionics-controlled magnetism is highly promising towards switching magnetism on and off magnetism at the touch of a button and efficient low-power-consumption spintronic devices. It can be achieved through the doping of ions, such as O2- and Li+, into reactive magnetic materials. The advantages of a solid-state electrolyte far exceed those of a conventional electrolyte. Here, we utilize the all-solid-state Li+ redox capacitor structure to modulate the magnetism of amorphous Co40Fe40B20 thin films. The change in magnetism of Co40Fe40B20 due to lithiation-delithiation is investigated by measuring its magnetic hysteresis loop along the out-of-plane (in-plane) direction under the charge (discharge) state. Reversible saturation magnetization of 27% in Co40Fe40B20 thin films is achieved due to conversion reactions with Li+. Further lithiation causes the out-of-plane axis to become harder, and thus, leads to an increase in the magnetic anisotropy along the in-plane direction. This provides a means to control the magnetic properties of metallic magnetic thin films by solid-state ionics.