Tuning the Dynamics of Chiral Domain Walls of Ferrimagnetic Films by Magnetoionic Effects

The manipulation of magnetism with a gate voltage is expected to lead to the realization of energy -efficient spintronics devices and high-performance magnetic memories. Exploiting magnetoionic effects under micropatterned electrodes in solid-state devices adds the possibility of modifying magnetic prop-erties locally, in a nonvolatile and reversible way. Tuning magnetic anisotropy, magnetization and Dzyaloshinskii-Moriya interaction allows the modification "at will" of the dynamics of nontrivial mag-netic textures such as skyrmions and chiral domain walls in magnetic race tracks. In this work, we illustrate efficient magnetoionic effects in a ferrimagnetic Pt/Co/Tb/AlOx stack using a ZrO2 thin layer as a solid-state ionic conductor. When a thin layer of terbium is deposited on top of cobalt, it acquires a magnetic moment that aligns antiparallel to that of cobalt, reducing the effective magnetization. Below the micropat-terned electrodes, the voltage-driven migration of oxygen ions in ZrO2 toward the ferrimagnetic stack partially oxidizes the Tb layer, leading to the local variation not only of the magnetization, but also of the magnetic anisotropy and of the Dzyaloshinskii-Moriya interaction. This leads to a huge increase in the domain wall velocity, which varies from 10 m/s in the pristine state to 250 m/s after gating. This non-volatile and reversible tuning of the domain wall dynamics may lead to applications to reprogrammable memories or other devices.