Elemental Doping and Interface Effects on Spin–Orbit Torques in CoSi‐Based Topological Semimetal Thin Films

Abstract

This work reports on Ni and Fe doping and interface effects on spin–orbit torques (SOTs) generated from a topological semimetal CoSi. CoSi thin films grown on Al2O3(0001) substrates by magnetron co‐sputtering show the B20 structure with a texture in the [210] orientation even after Ni or Fe doping. The SOTs from the films exerted on the magnetization of a CoFeB layer are evaluated by harmonic Hall and spin‐torque ferromagnetic resonance measurements. The spin Hall efficiency ξSH of the textured B20‐CoSi at room temperature is determined to be 9.6%, which decreases to 1.8% for Ni0.15Co0.85Si and to 5.5% for Fe0.26Co0.74Si. The electrical conductivity dependence of the spin Hall conductivity is assigned to the regime of intrinsic mechanism of spin Hall effect, suggesting that the reduction of ξSH with the element doping can be due to the degradation in topological electronic structures of CoSi. Furthermore, inserting a Cu layer at the Co(Ni, Fe)Si/CoFeB interface results in an increase of the ξSH up to 10.9% for CoSi, 4.0% for Ni0.15Co0.85Si, and 8.3% for Fe0.26Co0.74Si. These enhancements of the ξSH can be attributed to the improvement in the interfacial spin transparency between the Co(Ni, Fe)Si and CoFeB layers.

Charge-to-spin conversion in fully epitaxial Ru/Cu hybrid nanolayers with interface control

“…the spin Hall effect (SHE), of the NM layer in the direction perpendicular to an applied charge current. When the spin current is injected into the FM layer, it can exert a torque on the magnetization of the FM layer, so-called spin-orbit torque (SOT), resulting in efficient magnetization switching with low energy consumption [11][12][13][14]. In addition, the spin accumulation at the interface of NM/FM induced by the injected spin current can alter the longitudinal resistance of the device, providing a spin-orbit-driven magnetoresistance [15,16].…”