Giant spin-orbit torque in a single ferrimagnetic metal layer

Antiferromagnets and compensated ferrimagnets offer opportunities to investigate spin dynamics in the 'terahertz gap' because their resonance modes lie in the 0:3 THz to 3 THz range. Despite some inherent advantages when compared to ferromagnets, these materials have not been extensively studied due to difficulties in exciting and detecting the high-frequency spin dynamics, especially in thin films. Here we show that spin-orbit torque in a single layer of the highly spin-polarized compensated ferrimagnet Mn₂RuxGa is remarkably efficient at generating spin-orbit fields μ0H_eff, which approach 0:1 × 10^-10Tm²/A in the low-current density limit-almost a thousand times the Oersted field, and one to two orders of magnitude greater than the effective fields in heavy metal/ferromagnet bilayers.