Self-generated spin-orbit torques driven by anomalous and planar Hall spin currents in Ni-Fe alloys

Recently discovered self-generated spin-orbit torques (SOTs) driven by planar and anomalous Hall effects in ferromagnetic conductors [1, 2] exhibit unusual angular dependences making them ideal candidates for energy-efficient spin torque nano-oscillators. However, the microscopic mechanisms underlying planar Hall torque (PHT) and anomalous Hall torque (AHT) remain unresolved. Here we report measurements of both PHT and AHT in a series of Ni-Fe alloy samples, where the magnitude of the SOTs is tuned by varying the alloy composition. By conducting simultaneous measurements of AHT and PHT in the same set of samples, along with qunatification the planar and anomalous Hall magneto-transport coefficients, we provide insights into the origin of these SOTs and offer strategies to maximize their magnitudes.



[1] C. Safranski, E. A. Montoya, I. N. Krivorotov, Nature Nanotech. 14, 27 (2019).

[2] E. A. Montoya, X. Pei, I. N. Krivorotov, arXiv:2401.05006 (2024).