We investigate the connections between current-induced spin-orbit torques and unidirectional magnetoresistance (UMR) by performing second harmonic longitudinal resistance measurements on Co/Pt bilayer with magnetic-field ${\mu }_{0}H$ up to 10 T and temperature $T$ down to 2 K. The fieldlike torque $h_{\mathrm{FL}}$ changes sign with varying Co thickness $t_{\mathrm{Co}}$, which indicates that competing mechanisms, i.e., the spin Hall effect (SHE) and the inverse spin galvanic effect (iSGE), are responsible for the generation of $h_{\mathrm{FL}}$. The sign of $h_{\mathrm{FL}}$ coincides with the sign of UMR induced by spin-dependent scattering. However, the dampinglike torque $h_{\mathrm{DL}}$ is proportional to the inverse Co thickness, with no sign reversal for all measured temperatures and $t_{\mathrm{Co}}$, indicating that $h_{\mathrm{DL}}$ originates solely from the SHE. The generation of $h_{\mathrm{DL}}$ via iSGE can be further excluded because of the observation of an $H$-linear dependence of UMR, which, in turn, indicates the negligible exchange coupling between spin accumulation and ferromagnetic metal.

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• Magnetoresistance
• Magnetotransport
• Rashba coupling
• Spin Hall effect
• Spin-orbit coupling