Superconductivity in Intermetallic W₇Re₁₃X (X=B and C) Compounds

抄録

We discovered superconductivity in W₇Re₁₃X (X=B and C) (T_c=7.1 K and 7.3 K, respectively), and their superconducting properties are discussed. The crystal structure of W₇Re₁₃X is β-Mn-type (cubic, space group: P4₁32), and Re atoms form a tilted octahedron. The magnetization (M–H) curves show typical type-II superconducting behavior, and the lower critical field H_c1(0), the upper critical field H_c2(0) and the Ginzburg–Landau (GL) parameter κ are 7.7 mT, 11.4 T and 54 for X=B and 4.0 mT, 12.6 T and 80 for X=C, respectively. From the specific heat measurement, the superconducting gap magnitudes are estimated to be 2Δ⁄k_BT_c=4.28 and 4.02, respectively.