Reduction of in-plane field required for spin-orbit torque magnetization reversal by insertion of Au spacer in Pt/Au/Co/Ni/Co/Ta

Abstract

Spin-orbit torques and current-induced switching are studied in perpendicularly magnetized Pt/Au/(Co/Ni/Co) films as a function of Au insertion layer thickness tAu. By simultaneously varying the ferromagnet layer thickness, a parametric series of samples with nearly constant anisotropy were prepared. On this series, spin orbit torques were characterized by harmonic voltage and hysteresis loop shift measurements, and current-induced switching was examined as a function of the in-plane bias field. Little variation is seen for tAu < 0.5 nm, whereas for tAu > 0.5 nm, a series of well-correlated effects appear. Both the loop shift efficiency and the Slonczewski-like spin-orbit torque effective field double, while the in-plane field required to saturate the loop shift efficiency decreases by a factor of ∼10. Correspondingly, the current and in-plane field required for spin-orbit torque switching are reduced by about 90%. These results suggest that a thin Au insertion layer reduces the Dzyaloshinskii-Moriya interaction strength and improves spin transmission at the spin Hall metal/ferromagnet interface, substantially reducing the in-plane field and currents for spin orbit torque switching.