Low-Temperature X-Ray Diffraction Studies of Near-Equiatomic VRu Alloys

A crystallographic transition of the ordered near-equiatomic VRu alloys has been observed between 360 and 110 K. This cubic-to-tetragonal distortion occurs over a temperature interval commensurate with the observed anomalies in electrical resistivity, magnetic susceptibility, and the Knight shift. The transition involves a 1.4% expansion in volume for ${\mathrm{V}}_{0.50}$ ${\mathrm{Ru}}_{0.50}$. This expansion is very nearly temperature independent between 300 and 110 K. The volume change for ${\mathrm{V}}_{0.51}$ ${\mathrm{Ru}}_{0.49}$ at 110 K is 1.5%. For both compounds the CsCl-type ordering is approximately 100%.