Non-Orthogonal Spin Current in PtMnGa

Abstract

An important goal of spintronics research is to discover efficient methods for generating spin currents. Generally, symmetry conditions constrain spin polarization to be orthogonal to both the charge and spin currents in nonmagnetic metals. However, certain systems with low structural symmetry may permit the generation of spin currents with different orientations. Here, the observation of non-orthogonal spin current in PtMnGa thin film is reported, where the composition gradient of Pt and Mn along the film normal direction results in mirror symmetry breaking about the film plane. Through second harmonic Hall (SHH) resistance, spin-torque ferromagnetic resonance (ST-FMR), and spin-orbit torques induced magnetization switching measurements on the PtMnGa/ferromagnets films, the robust generation of spin currents with s_x, s_y, and s_z polarizations in PtMnGa are confirmed, which is supported by density functional theory calculations. The spin Hall angles for the s_{i(i = x, y, z)} are calculated using both SHH and ST-FMR methods, yielding consistent results. Furthermore, a zero-field partial magnetization switching is realized in perpendicularly magnetized PtMnGa/Co/Pt multilayers due to the presence of s_x and s_z spin currents. These results demonstrate that the PtMnGa can be a promising spin current source, providing a key strategy for finding new device functionalities.