The interplay of large two-magnon ferromagnetic resonance linewidths and low Gilbert damping in Heusler thin films

TL;DR

This study investigates ferromagnetic resonance linewidths in Heusler thin films, revealing a large two-magnon scattering effect in-plane and low Gilbert damping out-of-plane, with implications for magnetic material quality and spintronic applications.

Contribution

It provides the first comprehensive analysis of the interplay between two-magnon scattering and Gilbert damping in epitaxial Heusler films, introducing a model that quantifies disorder effects.

Findings

Large anisotropic two-magnon linewidth broadening in-plane

Low Gilbert damping constants out-of-plane for all samples

Disorder lengthscale estimated at 10-100 nm

Abstract

We report on broadband ferromagnetic resonance linewidth measurements performed on epitaxial Heusler thin films. A large and anisotropic two-magnon scattering linewidth broadening is observed for measurements with the magnetization lying in the film plane, while linewidth measurements with the magnetization saturated perpendicular to the sample plane reveal low Gilbert damping constants of $(1.5\pm0.1)\times 10^{-3}$, $(1.8\pm0.2)\times 10^{-3}$, and $<8\times 10^{-4}$ for Co$_2$MnSi/MgO, Co$_2$MnAl/MgO, and Co$_2$FeAl/MgO, respectively. The in-plane measurements are fit to a model combining Gilbert and two-magnon scattering contributions to the linewidth, revealing a characteristic disorder lengthscale of 10-100 nm.