Current-induced macrospin vs spin-wave excitations in spin valves

TL;DR

This paper theoretically investigates how current-induced magnetic excitations in spin valves depend on wave mode, revealing that macrospin and spin-wave instabilities are influenced by device parameters and current direction.

Contribution

It provides analytic expressions for critical currents and clarifies the dependence of excitations on wave mode, device parameters, and current direction.

Findings

Torque and damping depend on spin wave wavelength.

Critical currents for excitation are analytically derived.

Macrospin and spin-wave instabilities depend on device parameters.

Abstract

The mode dependence of current-induced magnetic excitations in spin valves is studied theoretically. The torque exerted on the magnetization by transverse spin currents as well as the Gilbert damping constant are found to depend strongly on the wave length of the excitation (spin wave). Analytic expressions are presented for the critical currents that excite a selected spin wave. The onset of macrospin (zero wavelength) vs finite wavelength instabilities depends on the device parameters and the current direction, in agreement with recent experimental findings.