Damping of magnetization dynamics by phonon pumping

TL;DR

This paper theoretically explores how magnetic film dynamics can pump phonons into a non-magnetic contact, leading to enhanced damping with interference effects influenced by frequency, thickness, and material properties.

Contribution

It introduces a new theoretical model for phonon pumping in magnetic films, revealing interference patterns and dependencies not captured by traditional Gilbert damping.

Findings

Phonon pumping causes measurable damping enhancement.

Interference patterns depend on resonance frequency and film thickness.

The effect varies with magnetization direction and material parameters.

Abstract

We theoretically investigate pumping of phonons by the dynamics of a magnetic film into a non-magnetic contact. The enhanced damping due to the loss of energy and angular momentum shows interference patterns as a function of resonance frequency and magnetic film thickness that cannot be described by viscous ("Gilbert") damping. The phonon pumping depends on magnetization direction as well as geometrical and material parameters and is observable, e.g., in thin films of yttrium iron garnet on a thick dielectric substrate.