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

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 (T)-dependent SOT efficiencies are investigated in Sb2Te3/Ta/TbCo heterostructures with perpendicular magnetic anisotropy. The spin Hall angle θSH is around 0.16 at room temperature (RT), which is much higher than that of the control sample without TI. Moreover, as T decreases from RT down to 10 K, θSH exhibits a conspicuous 5-fold enhancement. Detailed analysis indicates that the θSH 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 θSH difference between 20 and 10 nm Sb2Te3 gradually shrinks with the increase of T, 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.