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 $({\ensuremath{\xi}}_{\mathrm{DL}}^{j})$ and the critical switching current density of perpendicularly magnetized spin-current generator-ferromagnet heterostructures. We find that the values of ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}$ based on switching current densities can either under- or overestimate ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}$ by up to 10 times in a domain-wall depinning analysis, while, in the macrospin analysis based on the switching current density, ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}$ can be overestimated by up to 1000 times. When comparing the relative strengths of ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}$ of spin-current generators, the critical switching current densities by themselves are a poor predictor.