Published by the American Physical Society through the American Institute of Physics
Physical Review B, Condensed Matter and Materials Physics vol:82 issue:9
We employed nuclear inelastic scattering of synchrotron radiation to measure the anisotropy in the phonon density of states of an FePt thin film ordered in the L1(0) phase and compared our results with ab initio calculations. We find a strong anisotropy in the phonon density of states along the a and c axes of the crystal, which induces a difference in the calculated thermodynamic and elastic parameters along these axes. Calculations of surface-related effects show that a strong deviation from the bulk vibrational spectrum is observed for an Fe-terminated surface. We deduce by comparison with our surface sensitive measurement that the FePt(100)-oriented surface is Pt terminated. This contrasts with a recent measurement on FePt nanoparticles, where additional low-energy modes are observed. The findings are expected to be representative of the lattice dynamics of L1(0) intermetallics.