Spin wave dynamics and the determination of intrinsic Gilbert damping in locally-excited Permalloy thin films

TL;DR

This study uses time-resolved Kerr microscopy and micromagnetic simulations to analyze spin wave dynamics in Permalloy thin films, accurately determining the intrinsic Gilbert damping parameter through magnetostatic spin wave analysis.

Contribution

It demonstrates that a single Gilbert damping constant can describe both volume and surface spin waves in Permalloy films, using a combined experimental and theoretical approach.

Findings

Consistent with magnetostatic spin wave theory

Intrinsic Gilbert damping parameter measured accurately

Nonuniform pulsed field influences spin wave modes

Abstract

Time-resolved scanning Kerr effect microscopy has been used to study magnetization dynamics in Permalloy thin films excited by transient magnetic pulses generated by a micrometer-scale transmission line structure. The results are consistent with magnetostatic spin wave theory and are supported by micromagnetic simulations. Magnetostatic volume and surface spin waves are measured for the same specimen using different bias field orientations and can be accurately calculated by k-space integrations over all excited plane wave components. A single damping constant of Gilbert form is sufficient to describe both scenarios. The nonuniform pulsed field plays a key role in the spin wave dynamics, with its Fourier transform serving as a weighting function for the participating modes. The intrinsic Gilbert damping parameter $\alpha$ is most conveniently measured when the spin waves are effectively stationary.