Temperature Dependence of Spin–Orbit Torques in Nearly Compensated Tb₂₁Co₇₉ Films by a Topological Insulator Sb₂Te₃

Abstract

Topological insulators (TIs) with spin-momentum-locked metallic surface states can exert giant spin-orbit torques, offering great potential in energy-efficient magnetic memory devices. In this work, temperature (<i>T</i>)-dependent SOT efficiencies are investigated in Sb₂Te₃/Ta/TbCo heterostructures with perpendicular magnetic anisotropy. The spin Hall angle θ_SH is around 0.16 at room temperature (RT), which is much higher than that of the control sample without TI. Moreover, as <i>T</i> decreases from RT down to 10 K, θ_SH exhibits a conspicuous 5-fold enhancement. Detailed analysis indicates that the θ_SH enhancement at reduced temperatures mainly results from the improved spin-polarized surface states, as evidenced from the continuously increased ratio of surface-to-bulk conduction. The θ_SH difference between 20 and 10 nm Sb₂Te₃ gradually shrinks with the increase of <i>T</i>, which is due to the increase of bulk state contribution. Our findings provide a deep insight into the spin transport mechanisms and robust charge-spin conversion in TIs.