Dynamic Simulation of the Energy Spectrum of Phonons in the Magnetic BCC Iron

Abstract

We used the symplectic and scalable algorithm for spin lattice dynamics embedded in LAMMPS to model the coupled relaxation processes of the spin and lattice subsystems to investigate the phonon dispersion of bcc Fe at T = 300 K. The atomic interactions were modelled via three semi-empirical many-body potentials within the embedded atom method, while the distance-dependent spin coupling relied on the Heisenberg-type Hamiltonian. In the state of mutual equilibrium of the spin and atom ensembles, we have calculated the dynamical matrix and the phonon spectra in bcc iron. We found that for a small to moderate wavevector absolute values, the phonon dispersion curves agree well with the experimental results obtained from inelastic neutron scattering, while discrepancies between theory and experiment were observed for larger wavevector values, particularly near the zone boundaries. Moreover, the impact of magnons on the phonon spectra is pronounced for all employed potentials.