Enhancement of spin–orbit torques by change in uniaxial in-plane magnetic anisotropy of Py/Pt bilayers on single crystal 128° Y-Cut LiNbO3 substrate

Abstract

We have investigated the correlations between the in-plane uniaxial magnetic anisotropy (Ku) and spin–orbit torque (SOT) of Ni80Fe20 (Py)/Pt thin films sputtered on a single-crystal 128° Y-Cut LiNbO3 (LNO) substrate by performing second-harmonic voltage measurements. The results show that the value of the damping-like (DL) SOT torque varies with the angle χ between Ku and the applied current and increases with χ from 0° to 90°. The effective spin Hall angle θSH, Pteff = 0.073 and 0.123 for χ = 0 and 90°, respectively, indicate a difference of approximately 1.7 times. The θSH,Pteff at χ = 90° is greater because the direction of the DL-SOT on the magnetization is the same as the Ku direction. This result implies that the effective spin Hall angle can be controlled by the Ku direction of the ferromagnetic metal layer induced on the LNO substrate, thereby providing valuable insight for the development of spin devices using SOT.