Efficient Current-Driven Perpendicular Magnetization Switching Through the Synergy of the Orbital and Spin Hall Effects.

Manipulating perpendicular magnetization via electrical current is a promising approach for developing low-power and ultrafast spintronic applications. However, the increasing difficulty with improving the efficiency associated with conventional spin-orbit torque mechanisms hinders the development of low-power spintronic device integration. In this study, we demonstrate highly efficient charge-to-spin conversion in NiNb alloys by integrating strong spin Hall effect form nickel (Ni) with strong orbital Hall (OHE) effect from niobium (Nb). By systematically tuning the alloy composition, the relative strengths of the orbital Hall effect and spin-orbit coupling (SOC) can be modulated, enabling controllable and enhanced efficiency of charge-to-spin conversion. The spin torque efficiency in NiNb alloys reaches as high as -1.4 to -1.7, with the maximum value observed at the equiatomic composition Ni50Nb50. Our results demonstrate that the integration of elements with intrinsically strong OHE and SOC is a promising way toward efficiency and controllable charge-to-spin conversion. This approach provides a generalizable routine for the material design of spin current sources for the next-generation spintronic devices.