Enhancing Spin–Orbit Torque Efficiency via Optimizing Pt‐Based Multilayers

Abstract

Spin–orbit torque (SOT) efficiencies are systematically investigated in [Pt (tPt)/Ru (1−tPt)]10/Pt (0.8 nm)/Co multilayer systems with perpendicular magnetic anisotropy and in‐plane magnetic anisotropy. A high SOT efficiency is achieved by the optimized Pt‐based multilayer structures. The maximum damping‐like efficiency ξDL of 0.31 is found in [Pt (tPt)/Ru (1−tPt)]10/Pt (0.8 nm)/Co multilayers with relatively low resistivity (58.8 μΩ cm), which is three times larger than that of pure Pt layer and is also significantly larger than the PtnRu1−n alloy with the same composition. Considering the interface transparency, intrinsic spin Hall ratio θSH of around 0.7, being close to the upper limit 0.8 for Pt‐based heavy metals, is obtained. The strongly enhanced ξDL is attributed to the high spin Hall conductivity contributed by the intrinsic spin Hall contribution and the enhanced resistivity due to enhanced interfacial scattering. This work provides a good balance of SOT efficiency and resistivity through the optimized Pt‐based multilayer structure, which is expected to be applicable in beyond Pt‐based systems and has great potential in building energy‐efficient SOT devices in the future.