Low-temperature galvanomagnetic, magnetic, and thermoelectric properties of Mo3Sb7-xTex (x=0.0, 0.3, 1.0, 1.6, and 1.8)

The galvanomagnetic, thermoelectric, and magnetic properties of some polycrystalline Mo3Sb7-xTex 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 Mo3Sb7. 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.