Current-induced magnetization switching in a CoTb amorphous single layer

Abstract

We demonstrate spin-orbit torque (SOT) switching of amorphous CoTb single-layer films with perpendicular magnetic anisotropy (PMA). The switching sustains even the film thickness is above 10 nm, where the critical switching current density stays almost constant. Without the need of overcoming the strong interfacial Dzyaloshinskii-Moriya interaction caused by the heavy metal, a quite low assistant field of \ensuremath{\sim}20 Oe is sufficient to realize the full switching. The SOT effective field decreases and undergoes a sign change with the decrease of the Tb concentration, implying that a combination of the spin Hall effect from both Co and Tb as well as an asymmetric spin current absorption accounts for the SOT switching mechanism. Our findings advance the use of magnetic materials with bulk PMA for energy-efficient and thermally stable nonvolatile memories, and add a different dimension for understanding the ordering and asymmetry in amorphous thin films.