# Atomistic Simulation of Phonon and Magnon Thermal Transport across the Ferro-Paramagnetic Transition

## TL;DR

This paper introduces a temperature-dependent simulation method combining atomic and spin dynamics to accurately model phonon and magnon thermal transport, including their interactions, across magnetic phase transitions, validated on body-centered cubic iron.

## Contribution

The study develops a novel Green-Kubo equilibrium approach that captures phonon-magnon interactions and thermal conductivities across the ferro-para magnetic transition, filling a key gap in thermal transport modeling.

## Key findings

- Successfully reproduces temperature-dependent thermal conductivities of BCC iron.
- High-frequency phonon-magnon scattering rates are significantly larger than low-frequency ones.
- The method aligns well with experimental measurements of non-electronic thermal conductivity.

## Abstract

A temperature-dependent approach involving Green-Kubo equilibrium atomic and spin dynamics (GKEASD) is reported to assess phonon and magnon thermal transport processes accounting for phonon-magnon interactions. Using body-center cubic (BCC) iron as a case study, GKEASD successfully reproduces its characteristic temperature-dependent spiral and lattice thermal conductivities. The non-electronic thermal conductivity, i.e., the sum of phonon and magnon thermal conductivities, calculated using GKEASD for BCC Fe agrees well with experimental measurements. Spectral energy analysis reveals that high-frequency phonon-magnon scattering rates are one order of magnitude larger than those at low frequencies due to energy scattering conservation rules and high densities of states. Higher temperatures further accentuate this phenomenon. This new framework fills existing gaps in simulating thermal transport across the ferro- to para-magnetic transition. Future application of this methodology to phonon- and magnon-dominant insulators and semiconductors will enhance understanding of emerging thermoelectric, spin caloritronic and superconducting materials.