Transport, thermal, and magnetic properties of the narrow-gap semiconductor CrSb₂

Resistivity, the Hall effect, the Seebeck coefficient, thermal conductivity, heat capacity, and magnetic susceptibility data are reported for CrSb₂ single crystals. In spite of some unusual features in electrical transport and Hall measurements below 100 K, only one phase transition is found in the temperature range from 2 to 750 K corresponding to long-range antiferromagnetic order below T_N ≈ 273 K. Many of the low-temperature properties can be explained by the thermal depopulation of carriers from the conduction band into a low-mobility band located approximately 16 meV below the conduction-band edge, as deduced from the Hall effect data. In analogy with what occurs in Ge, the low-mobility band is likely an impurity band. The Seebeck coefficient, S, is large and negative for temperatures from 2 to 300 K ranging from ≈-70μV/K at 300 K to -4500μV/K at 18 K. A large maximum in |S| at 18 K is likely due to phonon drag, with the abrupt drop in |S| below 18 K due to the thermal depopulation of the high-mobility conduction band. The large thermal conductivity between 10 and 20 K (≈350 W/m K) is consistent with this interpretation, as are detailed calculations of the Seebeck coefficient made using the complete calculated electronic structure. These data are compared to data reported for FeSb₂, which crystallizes in the same marcasite structure, and FeSi, another unusual narrow-gap semiconductor.