Spin–orbit torque characterization in a nutshell

Spin current and spin torque generation through the spin–orbit interactions in solids, of bulk or interfacial origin, is at the heart of spintronics research. The realization of spin–orbit torque (SOT) driven magnetic dynamics and switching in diverse magnetic heterostructures also pave the way for developing SOT magnetoresistive random access memory and other novel SOT memory and logic devices. Of scientific and technological importance are accurate and efficient SOT quantification techniques, which have been abundantly developed in the last decade. In this article, we summarize popular techniques to experimentally quantify SOTs in magnetic heterostructures at micro- and nano-scale. For each technique, we give an overview of its principle, variations, strengths, shortcomings, error sources, and any cautions in usage. Finally, we discuss the remaining challenges in understanding and quantifying the SOTs in heterostructures.