Spin-orbit torque and Dzyaloshinskii–Moriya interaction in 4d metal Rh-based magnetic heterostructures

The electrical switching of magnetization through spin–orbit torque (SOT) has potential applications for energy-efficient spintronic devices. Previous studies focused mostly on 5d heavy metals with strong spin–orbit coupling (SOC) to generate a spin current or a nonequilibrium spin accumulation and exert SOTs on the magnetization of a neighboring ferromagnetic layer. Recent theoretical and experimental studies indicated that 4d metals with weak SOC may also generate a sizable torque and realize the current-induced magnetization switching. In this work, we studied the current-induced SOTs in 4d metal Rh-based magnetic heterostructures with a perpendicular magnetic anisotropy. The damping-like SOT efficiency ξDL of [Ni/Co]3/Rh multilayers increases with the Rh thickness tRh and becomes saturated at tRh = 5 nm. Although the spin-Hall angle of Rh is rather small about 0.028 ± 0.005, a reversible current-induced SOT switching can still be achieved. In addition, the interfacial Dzyaloshinskii-Moriya interaction (iDMI) in Rh/Co heterostructures was quantitatively characterized by using Brillouin light scattering. The iDMI constant D increases with tRh and reaches 224 ± 39 μJ/m2 at tRh = 5 nm. Our results indicated that even for a weak SOC 4d metal Rh, it is still possible to obtain a current-induced magnetization switching and observe an obvious iDMI effect in the Rh-based magnetic heterostructures, which may broaden the scope of spintronic materials used for SOT devices.