Compositional variation of the phonon dispersion curves of bcc Fe-Ga alloys

Inelastic neutron scattering techniques have been used to measure the phonon dispersion curves of bcc Fe-Ga alloys as a function of Ga concentration. We observed that the phonon frequencies of every branch decrease significantly with increasing Ga concentration with the softening being more pronounced for the T$_{2}$[110] branch and for the L[111] in the vicinity of $\xi $ = (2/3, 2/3,2/3). The slope of the T$_{2}$[110] branch was found to decrease linearly with increasing Ga concentration and to extrapolate to zero at approximately 27 at.{\%} in agreement with the results of sound velocity measurements. As the Ga concentration increases, a splitting of the T$_{1}$[110] branch is observed, an effect characteristic of diatomic lattices.