Field-Free Spin-Orbit Torque Switching in Perpendicularly Magnetized Ta/CoFeB/MgO/NiO/Ta with a Canted Antiferromagnetic Insulator NiO Interlayer

In this study, deterministic current-induced spin-orbit torque (SOT)magnetization switching is achieved, particularly in systems withperpendicular magnetic anisotropy (PMA), without the need for a collinearin-plane field, a traditionally challenging requirement. In aTa/CoFeB/MgO/NiO/Ta structure, spin reflection at the MgO/NiO interfacegenerates a spin current with an out-of-plane spin polarization component z .Notably, the sample featuring 0.8 nm MgO and 2 nm NiO demonstrates animpressive optimal switching ratio approaching 100% without any in-planefield. A systematic investigation of the effects of the MgO and NiO thicknessdemonstrates that the formation of noncollinear spin structures and cantedmagnetization in the ultrathin NiO interlayer plays a pivotal role to thefield-free SOT switching. The integration of NiO as an antiferromagneticinsulator effectively mitigates current shunting effects and enhances thethermal stability of the device. This advancement in the CoFeB/MgO systemholds promise for significant applications in spintronics, marking a crucialstep toward realizing innovative technologies