Spin Wave Excitation in Magnetic Insulator Thin Films by Spin-Transfer Torque

TL;DR

This paper investigates how spin currents can excite dipole-exchange spin waves in magnetic insulator thin films, highlighting the role of surface anisotropy and interface quality in optimizing excitation efficiency.

Contribution

It introduces the impact of surface anisotropy and spin pumping on surface spin wave modes, providing insights for efficient spin wave excitation in magnetic insulators.

Findings

Surface anisotropy induces non-chiral surface spin wave modes.

Penetration depth of surface modes is inversely proportional to anisotropy strength.

High interface quality reduces the influence of spin pumping on excitation spectrum.

Abstract

We describe excitation of dipole-exchange spin waves in insulating magnetic thin films by spin current injection at the surface of the film. An easy-axis magnetic surface anisotropy can induce a non-chiral surface spin wave mode with penetration depth inversely proportional to the strength of the surface anisotropy, which strongly reduces the critical current and enhances the excitation power. The importance of the interface spin wave modes on the excitation spectrum is reduced by spin pumping, which depends on the quality of the interface as expressed by the spin mixing conductance.