\textit{Ab initio} study on spin fluctuations of itinerant kagome magnet FeSn

TL;DR

This study combines advanced theoretical methods to analyze spin fluctuations in FeSn, revealing Landau damping as the cause of high-energy magnon damping and explaining high-energy magnon features.

Contribution

It introduces a combined approach of linear spin wave theory and density functional perturbation theory to explain high-energy magnon damping in FeSn.

Findings

High-energy magnon damping is due to Landau damping.

High-energy optical-magnon branches are linked to low Stoner excitation.

Theoretical spectra match experimental observations.

Abstract

Kagome antiferromagnetic metal FeSn has become an attracting platform for the exploration of novel electronic states, such as topological Dirac states and the formation of flat bands by localized electrons. Apart from the electronic properties, Dirac magnons and flat magnon bands have also been proposed by applying simplified Heisenberg models to kagome magnetic systems.Inelastic neutron scattering studies on FeSn found well defined magnon dispersions at low energies,but magnons at high energies are strongly dampled, which can not be explained by localized spin models. In this paper, we utilize both linear spin wave theory and time-dependent density functional perturbation theory to investigate spin fluctuations of FeSn. Through the comparison of calculated spin wave spectra and Stoner continuum, we explicitly show that the damping of magnons at high energies are due to the Landau damping, and the appearance of high energy optical-magnon like branches at the M and K point are resulted by relatively low Stoner excitation intensity at those regions.