Giant Spin Hall Effect in Cu–Tb Alloy Thin Films

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.