Influence of non-local damping on magnon properties of ferromagnets

TL;DR

This study investigates how non-local damping influences magnon properties in various ferromagnetic alloys, revealing that it can either decrease or increase magnon lifetimes depending on the material, with implications for magnetic damping models.

Contribution

It provides the first detailed analysis of non-local damping effects on magnon lifetimes in Fe, Co, Ni, and Fe-Co alloys using advanced electronic structure calculations.

Findings

Non-local damping decreases magnon lifetimes in Fe, Co, Ni.

In Fe-Co alloys, non-local damping can increase magnon lifetimes.

Good agreement between spin dynamics and linear response methods.

Abstract

We study the influence of non-local damping on magnon properties of Fe, Co, Ni and Fe$_{1-x}$Co$_{x}$ ($x=30\%,50\%$) alloys. The Gilbert damping parameter is typically considered as a local scalar both in experiment and in theoretical modelling. However, recent works have revealed that Gilbert damping is a non-local quantity that allows for energy dissipation between atomic sites. With the Gilbert damping parameters calculated from a state-of-the-art real-space electronic structure method, magnon lifetimes are evaluated from spin dynamics and linear response, where a good agreement is found between these two methods. It is found that non-local damping affects the magnon lifetimes in different ways depending on the system. Specifically, we find that in Fe, Co, and Ni the non-local damping decreases the magnon lifetimes, while in $\rm Fe_{70}Co_{30}$ and Fe$_{50}$Co$_{50}$ an opposite, non-local damping effect is observed, and our data show that it is much stronger in the former.