SPINTEC, University Grenoble Alpes, CEA, CNRS, Grenoble INP, INAC-Spintec, Grenoble, France, Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, Vandoeuvre lès Nancy, France, CEA, LETI, MINATEC Campus, Grenoble, France, Department of Physics, Institute of Applied Physics, Seoul National University, Seoul, South Korea, LSPM (CNRS-UPR 3407), Université Paris 13, Sorbonne Paris Cité, 99 avenue Jean-Baptiste Clément, Villetaneuse, France, Center for X-ray Optics, Lawrence Berkeley National Laboratoryc, Berkeley, CA, United States, Department of Materials Science and Engineering, Korea University, Seoul, South Korea

We investigate spin-orbit torque (SOT)-induced switching in rare-earth-transition metal ferrimagnetic alloys using W/CoTb bilayers. The switching current is found to vary continuously with the alloy concentration, and no reduction in the switching current is observed at the magnetic compensation point despite a very large SOT efficiency. A model based on coupled Landau-Lifschitz-Gilbert (LLG) equations shows that the switching current density scales with the effective perpendicular anisotropy which does not exhibit strong reduction at the magnetic compensation, explaining the behavior of the switching current density. This model also suggests that conventional SOT effective field measurements do not allow one to conclude whether the spins are transferred to one sublattice or just simply to the net magnetization. The effective spin Hall angle measurement shows an enhancement of the spin Hall angle with the Tb concentration which suggests an additional SOT contribution from the rare earth Tb atoms. © 2018 Author(s).

Ferrimagnetism, Orbits, Rare earths, Switching, Transition metal alloys, Transition metals, Tungsten, Alloy concentration, Effective field, Magnetic compensation, Model-based OPC, Perpendicular anisotropy, Rare earth transition metal, Switching current density, Switching currents, Rare earth alloys