Thermal Contribution to the Spin-Orbit Torque in Metallic-Ferrimagnetic Systems

Abstract

We report a systematic study of current-induced perpendicular magnetization switching in W/Co$_{x}$Tb$_{1-x}$/Al thin films with strong perpendicular magnetic anisotropy. Various Co$_{x}$Tb$_{1-x}$ ferrimagnetic alloys with different magnetic compensation temperatures are presented. The systems are characterized using MOKE, SQUID and anomalous Hall resistance at different cryostat temperature ranging from 10 K to 350 K. The current-switching experiments are performed in the spin-orbit torque geometry where the current pulses are injected in plane and the magnetization reversal is detected by measuring the Hall resistance. The full reversal magnetization has been observed in all samples. Some experimental results could only be explained by the strong sample heating effect during the current pulses injection. We have found that, for a given composition $x$ and switching polarity, the devices always reach the same temperature $\textit{T}_{switch}(x)$ before switching independently of the cryostat temperature. $\textit{T}_{switch}$ seems to scale with the Curie temperature of the Co$_{x}$Tb$_{1-x}$ ferrimagnetic alloys. This explains the evolution of the critical current (and critical current density) as a function of the alloy concentration. Future application could take advantages of this heating effect which allows reducing the in-plane external field. Unexpected double magnetization switching has been observed when the heat generated by the current allows crosses the compensation temperature.