Inelastic neutron scattering and migration energies in FePd

The frequencies of the normal modes of vibration of FePd single crystal have been measured using inelastic neutron scattering. The measurements were performed for the L10 ordered structure at 300 and 860 K and for the fcc disordered state at 1020 K. A general lowering of phonon frequencies with increasing temperature is found in FePd, the dependence being the strongest for acoustical transverse [ξ ξ ξ] branches. The migration energies as well as several thermodynamic quantities have been calculated from the densities of states. The contribution of ordering to the migration energy, as experimentally determined in this work, agrees well with the obtained one by Monte Carlo simulations in the L10 structure.