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

TL;DR

This study reveals that for micrometer-sized heterostructures, there is no straightforward link between spin-orbit torque efficiency and switching current density, complicating the evaluation of magnetic switching performance.

Contribution

It demonstrates that switching current density is an unreliable predictor of spin-orbit torque efficiency in perpendicularly magnetized heterostructures, highlighting the need for more comprehensive analysis methods.

Findings

{\xi}_DL^j can be over- or under-estimated by large factors depending on analysis method.

Switching current density alone poorly predicts spin-orbit torque efficiency.

No simple correlation exists between torque efficiency and switching current in studied 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.