Anatomy of Spin-Orbit Torque

Vivek Amin, NIST

May 5, 2020

Information and communications technology is predicted to account for 10% to 20% of the world’s power consumption within a decade. Alleviating this rise in power consumption requires rethinking the way we electronically process and store information. Spintronics offers a possible solution to this problem by using spin currents or spin waves rather than conventional charge currents to manipulate information. A key ingredient in spintronics is spin-orbit coupling: the relativistic coupling between a particle’s spin and orbital moments. Spin-orbit coupling permits conduction electrons to extract a virtually unlimited amount of angular momentum from the crystal lattice, potentially enabling energy efficient information processing. In this talk, I will discuss the electrical manipulation of a ferromagnet’s magnetization through spin-orbit coupling. This phenomenon, known as spin-orbit torque, could help harness some of the advantages of different electronic memories (e.g. speed, nonvolatility, radiation hardness) into one device. I review the traditional spin-orbit torque mechanisms and then show that novel interfacial or bulk effects are needed to explain recent experiments. Shedding light on these mechanisms will help clarify the nature of spin-orbit torque, creating exciting new possibilities for current-controlled magnetization dynamics with attractive applications for information processing.