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 Sb 2 Te 3 /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 T 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 Sb 2 Te 3 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.

Figure 4. a) The out-of-plane magnetic hysteresis loops for the [Co/Ni] N /TbCo samples of N = 0, 1, and 2 measured at room temperature. Panels (b) and (c) respectively show the temperature dependences of χ DL and 1/M S for the samples of N = 0 and N = 2. d) Temperature dependences of the spin-orbit torque efficiency |ξ DL |. www.advancedsciencenews.com

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Magnetic precession with enhanced frequency and amplitude is achieved by controlling tCu and N in perpendicular [Pd/Co]5/Cu(tCu)/[Co/Ni]N films.

Spin–orbit torque (SOT), exerted to a ferromagnet from an adjacent non-magnetic layer, has been widely considered as a promising strategy to realize spintronic devices with high energy efficiency, endurance, and speed. Much effort has been devoted to the search for materials and structures that can generate strong SOTs. Recent investigations showed that two-dimensional (2D) transition metal dichalcogenides provide the potential to produce strong enough SOTs to manipulate the magnetic devices due to rich spin-dependent properties. Here, we present the study of SOT in WTe2/ferromagnet with perpendicular magnetic anisotropy devices, and an enhancement of SOT efficiency with the thickness of WTe2 is observed, which may be ascribed to the spin absorption at the WTe2/Ta interface and the spin Hall effect. This work demonstrates the possibility of manipulating magnetization by 2D materials and an avenue for engineering spintronic devices based on 2D materials.