Lattice dynamics of face-centered-cubicCo0.92Fe0.08

The room-temperature lattice dynamics of a crystal of ${\mathrm{Co}}_{0.92}$ ${\mathrm{Fe}}_{0.08}$ were studied with a view to understanding the fcc-hcp transition which occurs in pure Co at ∼415°C. Because the martensitic transformation lies well below 77°K for this alloy, no anomalous neutron scattering was observed. We did, however, measure a complete set of phonon dispersion curves and obtained a set of Born-von Kármán force constants from which the usual thermodynamic data have been derived. As the masses of Fe and Co are so similar, these results should represent the lattice dynamics for fcc cobalt.