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

A rigorous temperature-dependent approach involving Green-Kubo equilibrium spiral and atomic dynamics (GK-ESAD) 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, GK-ESAD successfully reproduces its characteristic temperature-dependent spiral and lattice thermal conductivities. The non-electronic thermal conductivity, i.e., the summation of phonon and magnon thermal conductivities, calculated using GK-ESAD for BCC Fe agrees well with experimental measurements. Spectral energy analysis shows that high-frequency phonon-magnon scattering rates are found to be one order magnitude larger than those at low frequencies due to energy scattering conserving rules and high density 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 our understanding of emerging thermoelectric, spin caloritronic and superconducting materials.