Electronic Transitions in Near-Equiatomic Vanadium-Ruthenium Alloys

The electrical resistivity, the magnetic susceptibility, and the Knight shift of $V^{51}$ have been studied as a function of temperature in near-equiatomic V-Ru alloys. Electronic transitions were observed as evidenced by the following anomalies: Over a narrow temperature range, the resistivity increases sharply, the susceptibility decreases rapidly, and the Knight shift increases during cooling. At the same time, a tetragonal crystallographic distortion occurs, as found by Marezio et al. The low-temperature specific heat and the superconducting transition temperature were found to vary drastically over the concentration region of interest in agreement with the results of previous work. These changes in electronic properties can be consistently interpreted as arising from a substantial reduction in the Fermi-surface area and of the effective number of carriers associated with the tetragonal distortion. This further suggests that the tetragonal phase is stabilized by the reduction of the electronic free energy.