Spin-Orbit Torques in ferrimagnetic GdFeCo

Recently spin-orbit torques in antiferromagnets received a lot of attention due to intrinsic high frequency dynamics as well as robustness against perturbations from external magnetic fields. Here, we report on spin-orbit torque (SOT) switching in ferrimagnetic \linebreak \mbox{Gd$_{x}($Fe$_{90}$Co$_{10})_{100-x}$} films on both sides of the magnetic compensation point~[1]. In addition to current driven switching experiments we performed harmonic Hall measurements of the effective SOT fields. We find that both the Slonczewski torque as well as the field-like torque diverge at the magnetization compensation point. However, the effective spin Hall angle $\xi=(2|e|/\hbar)M_S t_{FM} (H_{eff}/|j_{HM}|)$ is found to be roughly constant across the investigated composition range. This provides important insight into the the angular momentum transfer process in ferrimagnets.\\ \\ $[1]$ Roschewsky, N. et al. \textit{Applied Physics Letters}, 109(11), 2016.