Impact of surface oxidation on gilbert damping and inverse spin hall effect in SiO2/Ta/NiFe multilayers

Abstract

Spin pumping in bilayer systems composed of ferromagnetic materials (FM) and heavy metals (HM) generates spin currents that can be detected by the inverse spin Hall effect (ISHE). Here, the reduction in Gilbert's damping (a) during spin pumping and the ISHE in the SiO2/Ta (tnm)/NiFe (10nm) bilayer system was observed. The value of a for SiO2/NiFe (10 nm) was determined to be 0.0121 + 0.0003. However, for SiO2/Ta (t nm)/NiFe (10 nm), a consistently lower damping across all Ta thicknesses was observed, which could be due to non-equilibrium spin accumulation at the interface. Additionally, high interfacial spin mixing conductance values of -1.83(+0.05) x 1019 m-2 and a spin diffusion length (ASD) of 2.77+0.53 nm was obtained. Further high inverse spin Hall voltage was recorded and the spin Hall angle of -0.024 was calculated for the Ta 7 nm system.