Lattice dynamics of NiAl3

Abstract

The intermetallic compound Ni${}_3{}^{}{}_{}{}^{}\mathrm{Al}$ orders in the Cu${}_3{}^{}{}_{}{}^{}\mathrm{Au}$ structure, and it is generally believed to be a weak itinerant ferromagnet. However, the presence of any magnetic inhomogeneities, as suggested by specific-heat measurements, cannot be easily understood within the framework of an itinerant electron theory. In the present work inelastic neutron scattering techniques have been used to study the room-temperature phonon dispersion curves of Ni${}_3{}^{}{}_{}{}^{}\mathrm{Al}$. The force constants obtained by fitting the experimental data to a three-nearest-neighbor Born-von Kármán model were used to evaluate the phonon density of states and the lattice specific heat. We find that the electronic specific heat of Ni${}_3{}^{}{}_{}{}^{}\mathrm{Al}$ (obtained by subtracting the lattice contribution from the measured total specific heat) does not exhibit any anomalous features at low temperature. Thus, within experimental precision, we do not find any evidence for the presence of magnetic inhomogeneities in Ni${}_3{}^{}{}_{}{}^{}\mathrm{Al}$.