Low-temperature galvanomagnetic, magnetic, and thermoelectric properties ofMo3Sb7−xTex(x=0.0, 0.3, 1.0, 1.6, and 1.8)

Abstract

The galvanomagnetic, thermoelectric, and magnetic properties of some polycrystalline ${\text{Mo}}_{3}{\text{Sb}}_{7\ensuremath{-}x}{\text{Te}}_{x}$ compounds ($x=0.0$, 0.3, 1.0, 1.6, and 2.2) have been experimentally investigated from 2 to 350 K. These samples were prepared via a metallurgical route, and characterized by x-ray diffraction and electron probe microanalysis. Experiments were completed by theoretical information including dispersion curves, and total and partial densities of states within the framework of the Korringa-Kohn-Rostoker method with the coherent-potential approximation. These theoretical aspects have highlighted a shift of the Fermi level toward the valence-band edge with increasing $x$ that can be understood within a rigid-band model. Transport property measurements have not only provided compelling evidence for this picture but have also shown that their variations with the Te content is consistent with a progressive crossover from a metalliclike to a semiconductinglike state as theoretically suggested. The enhancement of the thermal conductivity as $x$ increases constitutes one of the most impressive properties of this system. This surprising behavior is tentatively ascribed to the disappearance of a strong scattering of phonons by magnetic excitations displayed by ${\text{Mo}}_{3}{\text{Sb}}_{7}$. The compositional evolution of the magnetic properties has brought further evidence of a progressive suppression of these magnetic excitations as the Te concentration increases. In addition, magnetic susceptibility together with specific-heat measurements have confirmed the decrease in the total density of states at the Fermi level with $x$ suggested by our band-structure calculations.