Lack of Simple Correlation between Switching Current Density and Spin-Orbit-Torque Efficiency of Perpendicularly Magnetized Spin-Current-Generator-Ferromagnet Heterostructures

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

Automated summary

Research shows that there is no simple correlation between the efficiency of dampinglike spin orbit torque and the critical switching current density of perpendicularly magnetized spin-current generator-ferromagnet heterostructures, especially in micrometer-sized samples. The values of efficiency based on switching current densities can sometimes severely underestimate or overestimate the actual efficiency, making critical switching current densities alone a poor predictor of the relative strength of spin-current generators.