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Single crystals of a quaternary system based on (Sb0.75Bi0.25)2Te3 doped with In were prepared using the Bridgman technique. Samples with varying contents of In were characterized by the measurements of electrical conductivity σ⊥c, Hall coefficient RH(B∥c), Seebeck coefficient S(ΔT⊥c), and thermal conductivity κ(ΔT⊥c). The measurements indicate that by incorporating In in (Sb0.75Bi0.25)2Te3 one lowers the concentration of free holes. This effect is explained in terms of a point defect model in the crystal lattice. We also discuss the temperature dependence of the thermoelectric figure of merit Z=σS2/κ of the samples. It is observed that low concentrations of In atoms in the (Sb0.75Bi0.25)2Te3 crystal lattice result in a substantial increase in the parameter Z in the temperature region 100–300 K. [ABSTRACT FROM AUTHOR]

Single crystals of Sb2Te3 doped with Cr (cCr=0–6×1020 cm-3) were prepared by the Bridgman method. The measurements of the Hall coefficient reveal a nonmonotonous dependence of hole concentrations on the Cr content in the crystal. The hole concentration decreases at low content of Cr, while at higher content of Cr it increases again. However, according to magnetic measurements, Cr atoms enter the structure and form uncharged substitutional defects CrSb×, which cannot affect the free carrier concentration directly. The observed dependence can be elucidated by means of a point defect model. The model is based on an assumption that defect structure of Sb2Te3 can be treated as hybrid Schottky and antisite defect disorder. Thus, we assume an interaction of CrSb× with the most populated native defects in the structure—antisite defects SbTe-1 and vacancies in the Te sublattice VTe+2. [ABSTRACT FROM AUTHOR]

The authors report on the hydrostatic pressure dependence of the magnetotransport properties of ferromagnetic Sb2-xVxTe3 single crystals with x=0.02–0.03. Pressure significantly increases the free hole concentration in these compounds. In turn, the Curie temperature is suppressed by roughly 40%, which goes against many models that would predict an increase in Curie temperature with increasing carrier concentration. These results indicate that the ferromagnetism in these materials is carrier mediated and that a full Ruderman-Kittel-Kasuya-Yosida model that takes into account the oscillatory nature of the indirect exchange interaction among localized spins is needed in order to explain the data. [ABSTRACT FROM AUTHOR]