Giant Spin Hall Effect in Cu-Tb Alloy Thin Films.

Abstract

We report the giant spin current generation in CuTb alloys arising from the spin Hall effect. The maximum spin Hall angle from our CuTb-based magnetic heterostructures was found to be -0.35 ± 0.02 for Cu0.39Tb0.61. We find that the contribution of skew scattering is larger than the side jump for lower Tb concentrations (<14.9%), while the converse is true for higher Tb concentrations. Additionally, we also studied the Gilbert damping parameter, spin diffusion length, and spin-mixing conductance. Interfacial spin transparency was found to be 0.55 ± 0.03 for the CoFeB/Cu0.53Tb0.47 interface. The spin diffusion length and spin-mixing conductance of the Cu0.53Tb0.47 alloy are λsd = 2.5 ± 0.3 nm and G↓↑ = (24.2 ± 1.0) × 1015 cm-2, respectively. Our results pave a way for rare-earth metals to be used as a spin Hall material in highly efficient SOT devices.