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

Abstract

We report large field-like torques with non-negligible damping-like torques in sputtered, amorphous Ru2Sn3 thin films. We confirm the amorphous structure of the films with high resolution tunneling electron microscopy and the 2:3 composition with Rutherford backscattering techniques. Through the second harmonic Hall measurement we can extract and characterize the damping-like (DL) and field-like (FL) SOTs originating in the Ru2Sn3 films. We find room temperature a DL torque efficiency of 0.14 ± 0.008 and 0.07 ± 0.012 and a FL torque efficiency of -0.03 ± 0.006 and -0.20 ± 0.009 for 4 and 10 nm Ru2Sn3 films respectively. By analyzing the resistivity dependence of the spin torque efficiencies, we extracted the contributions from the intrinsic and extrinsic spin Hall effects. The FL torques show dominant contributions from the intrinsic spin Hall effect with intrinsic spin conductivity up to -240 ± 19 (Ωcm)-1 while the DL torques show dominate contributions from the extrinsic spin hall effects with sum of the skew scattering and side jump up to -175 ± 19 μΩcm. We performed macro-spin calculations of the LLGS equation to simulate switching a perpendicular magnetic layer including both the DL and FL torques generated from our Ru2Sn3 SOT channel. We find the inclusion of FL toques three times greater than the DL can reduce the critical current required for switching and the switching time by almost 50% compared to the DL torque only case.