Large fieldlike torque in amorphous Ru2Sn3 originated from the intrinsic spin Hall effect

We investigated temperature dependent current driven spin-orbit torques in magnetron sputtered ${\mathrm{Ru}}₂{\mathrm{Sn}}₃$ (4 and 10 nm)/${\mathrm{Co}}₂₀{\mathrm{Fe}}₆₀{\mathrm{B}}₂₀$ (5 nm) layered structures with in-plane magnetic anisotropy. The room temperature dampinglike and fieldlike spin torque efficiencies of the amorphous ${\mathrm{Ru}}₂{\mathrm{Sn}}₃$ films were measured to be $0.14\ifmmode\pm\else\textpm\fi{}0.008\phantom{\rule{0.16em}{0ex}}(0.07\ifmmode\pm\else\textpm\fi{}0.012)$ and $--0.03\ifmmode\pm\else\textpm\fi{}0.006\phantom{\rule{0.16em}{0ex}}(--0.20\ifmmode\pm\else\textpm\fi{}0.009)$, for the four (10 nm) films, respectively, by utilizing the second-harmonic Hall technique. The large fieldlike torque in the relatively thicker ${\mathrm{Ru}}₂{\mathrm{Sn}}₃$ (10 nm) thin film is unique compared to the traditional spin Hall materials interfaced with thick magnetic layers with in-plane magnetic anisotropy which typically have dominant dampinglike and negligible fieldlike torques. Additionally, the observed room temperature fieldlike torque efficiency in ${\mathrm{Ru}}₂{\mathrm{Sn}}₃$ (10 nm)/CoFeB (5 nm) is up to three times larger than the dampinglike torque ($--0.20\ifmmode\pm\else\textpm\fi{}0.009$ and $0.07\ifmmode\pm\else\textpm\fi{}0.012$, respectively) and 30 times larger at 50 K ($--0.29\ifmmode\pm\else\textpm\fi{}0.014$ and $0.009\ifmmode\pm\else\textpm\fi{}0.017$, respectively). The temperature dependence of the fieldlike torques shows dominant contributions from the intrinsic spin Hall effect while the dampinglike torques show dominate contributions from the extrinsic spin Hall effects, skew scattering, and side jump. Through macrospin calculations, we found that including fieldlike torques on the order of or larger than the dampinglike torque can reduce the switching critical current and decrease magnetization procession for a perpendicular ferromagnetic layer.