Epitaxial thin bilayers NiPt/FePt/MgO(001) were grown at 700K and annealed at 800 and 900K. At 800K, the L10 long-range order increased without measurable interdiffusion. At 900K, interdiffusion took place without destroying the L10 long-range order. This surprising observation could be explained by different diffusion mechanisms that were energetically compared using molecular dynamics simulations in CoPt in the second moment tight binding approximation. In addition, the frequencies of the normal modes of vibration were measured in FePd, CoPt and FePt single crystals using inelastic neutron scattering. The measurements were performed in the L10 ordered structure at 300K. From a Born-von Karman fit, the phonon densities of states were calculated. The migration energies in the 3 systems were estimated using the model developed by Schober et al. (1981). The phonon densities of states had also been used to calculate several thermodynamic quantities as the vibration entropy and the Debye temperature.Atomic Migration in Bulk and Thin Film L10 Alloys: Experiments and Molecular Dynamics Simulations. Pierron-Bohnes, V., Montsouka, R.V.P., Goyhenex, C., Mehaddene, T., Messad, L., Bouzar, H., Numakura, H., Tanaka, K., Hennion, B.: Defect and Diffusion Forum, 2007, 263, 41-50