Finite temperature magnon spectra in yttrium iron garnet from mean field approach in tight-binding model

TL;DR

This paper models finite temperature magnon spectra in yttrium iron garnet using a tight-binding approach and mean field approximation, revealing temperature-dependent spin wave gaps consistent with experiments.

Contribution

It introduces a mean field approach within a tight-binding model to analyze finite temperature magnon spectra in yttrium iron garnet, highlighting differences at two iron atom sites.

Findings

Temperature-dependent spin wave gap matches experimental data

Only two magnon modes are relevant to ferromagnetic resonance

Spin reduction varies at different iron atom sites

Abstract

We study magnon spectra at finite temperature in yttrium iron garnet from tight-binding model with nearest neighboring exchange interaction. The spin reduction due to thermal magnon excitation are taken into account via the mean field approximation to the local spin and found to be different at two sets of iron atoms. The resulting temperature dependence of the spin wave gap shows good agreement with experiment. We find only two magnon modes are relevant to ferromagnetic resonance.