Current-induced spin-orbit torque and thermal effects in CoFe/Pt heterostructures via second and third harmonic Hall measurements
Phys. Rev. B 112, 224424 – Published 12 December, 2025
DOI: https://doi.org/10.1103/b4gw-81cf
Abstract
The coexistence of current-induced spin-orbit torque (SOT) and thermal effects necessitates their disentanglement for the realization of device applications. The second harmonic Hall voltage is widely used to study electrically driven spin torques and thermoelectric (anomalous Nernst effect) and/or thermomagnetic (spin Seebeck effect) effects in ferromagnet (FM)/heavy metal (HM) heterostructures. On the other hand, the third harmonic voltage has recently been considered for studying nonlinear SOT effects, thermally induced magnetization modulation, and SOT in antiferromagnet (AFM)/HM heterostructures. Here, we studied third harmonic Hall voltage characterization in Pt/CoFe with a higher magnetostriction coefficient for CoFe (Co 66%, Fe 34%). Our experiments demonstrate that the third harmonic voltage reveals two key mechanisms behind thermally driven spin torques: thermal expansion via the magnetoelastic effect and thermally induced magnetization reduction. This highlights the third harmonic voltage as a powerful tool for exploring nonlinear effects in a FM/HM heterostructure.
