Temperature Dependence of the Hall Effect and Resistivity in Single Crystals of Mo and Nb and of Mo-Rich-Re, Mo-Nb, and Nb-Rich-Zr Alloys

Abstract

The Hall coefficients and resistivities of oriented single crystals of pure Mo and Nb and of an extended series of Mo-rich-Re, Mo-Nb, and Nb-rich-Zr alloy crystals were measured as a function of temperature between 295 and 4.2 K. The Hall coefficient $R$ varies with composition roughly as the reciprocal of the density of states at the Fermi level, exhibiting a large peak at about 5.8 outer electrons per atom. Sharp dips occur in $R$ for Mo and Nb between 20 and 40 K, which for the higher-purity Mo crystals are quite sensitive to the orientation of the magnetic field relative to the crystallographic axes. The temperature dependences of $R$ for the alloy crystals suggest that impurity scattering is more anisotropic than phonon scattering in Mo-Nb and Nb-rich Zr but less anisotropic than scattering by phonons in Mo-rich Re. A quantitative measure of the magnitudes of these anisotropies is obtained from a two-band analysis of the Mo-rich sample data using the rigid-band approximation in conjunction with calculated energy surfaces.