Crystalline phase dependence of the inverse spin Hall effect in Sb2Te3/CoFeB bilayers

Sb2Te3 is a layered material with the properties of both a topological insulator and a phase-change material. In this study, to investigate the relationship between the spin current-to-charge current conversion efficiency of Sb2Te3 and its phase, we fabricated Sb2Te3/CoFeB bilayers with varying Sb2Te3 thicknesses. The electromotive force induced at both ends of the bilayer was measured as a result of the scattering of the spin current injected into Sb2Te3 by spin pumping due to ferromagnetic resonance, the so-called inverse spin Hall effect (ISHE). Two different Sb2Te3 phases—crystalline and amorphous—were prepared, and the phase dependence of the ISHE was investigated. The ISHE of the crystalline Sb2Te3 film exhibited a strong dependence on thickness, whereas the amorphous phase showed only a minor variation with thickness. These findings contribute to the development of novel devices that exploit both the charge and spin degrees of freedom in topological insulator-based spintronic applications.