  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.
