Lack of simple correlation between switching current density and spin-orbit torque efficiency of perpendicularly magnetized spin-current generator/ferromagnet heterostructures

Abstract

Spin-orbit torque can drive electrical switching of magnetic layers. Here, we report that at least for micrometer-sized samples there is no simple correlation between the efficiency of dampinglike spin-orbit torque ({\xi}_DL^j) and the critical switching current density of perpendicularly magnetized spin-current generator/ferromagnet heterostructures. We find that the values of {\xi}_DL^j based on switching current densities can either under- or over-estimated {\xi}_DL^j by up to tens of times in a domain-wall depinning analysis, while in the macrospin analysis based on the switching current density {\xi}_DL^j can be overestimated by up to thousands of times. When comparing the relative strengths of {\xi}_DL^j of spin-current generators, the critical switching current densities by themselves are a poor predictor.