Thermal spin dynamics of yttrium iron garnet

TL;DR

This paper uses atomistic spin dynamics to analyze the full spin wave spectrum of yttrium iron garnet, revealing temperature-dependent effects on spin pumping and mode behavior that align with experimental observations.

Contribution

It introduces a comprehensive atomistic simulation approach to study all 20 spin wave modes in yttrium iron garnet, moving beyond simplified models.

Findings

Frequency dependence of modes matches neutron scattering data

Thermal occupation of optical modes reduces net spin pumping

Full mode spectrum analysis improves understanding of spin dynamics

Abstract

Yttrium Iron Garnet is the prototypical material used to study pure spin currents. It is a complex material with 20 magnetic atoms in the unit cell. Almost all theories and experimental analysis approximates this complicated material to a simple ferromagnet with a single spin wave mode. We use the method of atomistic spin dynamics to study the temperature evolution of the full 20 mode exchange spin wave spectrum. Our results show a strong frequency dependence of the modes in quantitative agreement with neutron scattering experiments. We find this causes in a reduction in the net spin pumping due to the thermal occupation of optical modes with the opposite chirality to the FMR mode.