Electrical-resistivity and low-temperature specific-heat measurements of single crystals of thiospinelCuV2S4

Zero-field and magnetic-field low-temperature specific-heat measurements have been carried out on single crystals of ${\mathrm{CuV}}_2$ ${\mathrm{S}}_4$. The electronic-specific-heat coefficient (in zero field) is found to be 62 mJ/mol ${\mathrm{K}}^2$ and the Debye temperature to be 205 K. A superconducting transition at 4.0 K has been reported in powder samples contaminated by an estimated 5 to 10 % sulvanite ${\mathrm{Cu}}_3$ ${\mathrm{VS}}_4$. Present experiments of the electrical resistivity and the specific heat, however, verify that high-quality single crystals do not exhibit a superconducting transition above 60 mK. Below 0.2 K, nuclear specific heat is observed. Applied magnetic fields increase the magnitude of the specific heat due to the nuclear Zeeman effect of V and Cu nuclei and the electric quadrupole interaction of Cu nuclei. The electric-field gradient at Cu nuclei is estimated to be eq=1.74×${10}^{22}$ V/${\mathrm{m}}^2$. Detailed analysis of the nuclear specific heat below 1.0 K is presented. A comparison of the theoretical analysis with the experimental result is given and are in excellent agreement.