Large field-like torque in amorphous Ru₂Sn₃ originated from the intrinsic spin Hall effect

We investigated temperature dependent current driven spin-orbit torques in magnetron sputtered Ru₂Sn₃ (4 and 10 nm) /Co₂₀Fe₆₀B₂₀ (5 nm) layered structures with in-plane magnetic anisotropy. The room temperature damping-like and field-like spin torque efficiencies of the amorphous Ru₂Sn₃ films were extracted to be as large as 0.14 ± 0.008 and -0.2 ± 0.009, respectively. The observed room temperature field-like torque efficiency in Ru₂Sn₃ (10 nm)/CoFeB (5 nm) is up to three times larger than the damping-like torque (-0.20 ± 0.009 and 0.07 ± 0.012, respectively) and thirty times larger at 50 K (-0.29 ± 0.014 and 0.009 ± 0.017, respectively). The temperature dependence of the field-like torques are unique and show dominant contributions from the intrinsic spin Hall effect with intrinsic spin conductivity up to -240 ± 19 (Ωcm)^-1 while the damping-like torques show dominate contributions from the extrinsic spin Hall effects with sum of the skew scattering and side jump up to -175 ± 19 (Ωcm)^-1. Through macro-spin calculations, we found that including field-like torques on the order or larger than the damping-like torque can reduce the switching critical current and the switching time for a perpendicular ferromagnetic layer.