Observation of the effects of ultra-thin Cr and Ti layers on spin–orbit torque and Dzyaloshinskii–Moriya interaction in Co/Ni/Pt system

We investigate the enhancement of spin–orbit torque (SOT) efficiency by inserting ultra-thin Cr or Ti layers into the interface of the Pt/Co stack in magnetic multilayer systems, specifically Pt/Co/Ni structures that provide skyrmions. Skyrmion generation requires both a sufficient Dzyaloshinskii–Moriya interaction (DMI) and high SOT efficiency to enable fast skyrmion transport. Our findings reveal that ultrathin Cr and Ti layers inserted between Pt and Co significantly enhance SOT efficiency, with Ti notably preserving DMI. We further demonstrate that the material selection of the insertion layer and its compatibility with the adjacent magnetic layer are critical. Thus, the insertion of an ultra-thin layer represents an attractive strategy for significantly improving SOT efficiency while maintaining DMI performance.