Spin‐transfer in High Magnetic Fields and Single Magnetic Layer Nanopillars

Abstract

This chapter reviews studies of the physics of spin transfer in high magnetic fields in bilayer and single magnetic layer nanopillars. The focus is on phenomena associated with the action of spin currents on the background magnetization of thin nanometer‐scale ferromagnetic layers, known as nanomagnets . Spin currents are shown to lead to magnetic hysteresis in large fields perpendicular to the layers in bilayer nanopillars. This is consistent with the standard model of spin transfer within a macrospin approximation. Spin‐transfer‐induced excitations also occur in single magnetic layer nanopillars. This shows that the most elementary samples that exhibit spin transfer consist of just a single thin magnetic layer, not two magnetic layers. Physics beyond the macrospin and one‐dimensional transport models is necessary to understand such excitations. Nonuniform spin‐wave excitations are also seen in the traditional bilayer structures, which experiments reveal to have a rich phase diagram of current‐induced magnetic excitations.