Spin-orbit torques and magnetization switching in Gd/Fe multilayers generated by current injection in NiCu alloys

Light transition metals have recently emerged as a sustainable material class for efficient spin-charge interconversion. We report measurements of current-induced spin-orbit torques generated by Ni${}_{1-x}$Cu${}_x$ alloys in perpendicularly magnetized ferrimagnetic Gd/Fe multilayers. We show that the spin-orbit torque efficiency of Ni${}_{1-x}$Cu${}_x$ increases with the Ni/Cu atomic ratio, reaching values comparable to those of Pt for Ni${}_{55}$Cu${}_{45}$. Furthermore, we demonstrate magnetization switching of a 20-nm-thick Gd/Fe multilayer with a threshold current that decreases with increasing Ni concentration, similar to the spin-orbit torque efficiency. Our findings show that Ni${}_{1-x}$Cu${}_x$$-$based magnetic heterostructures allow for efficient control of the magnetization by electric currents.