Superconductivity in W5SiB2 with the T2 Phase Structure

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We report here the superconducting properties of W5SiB2. W5SiB2 has a T2 phase structure with the space group I4/mcm. Magnetic susceptibility, electrical resistivity, and specific heat data show that W5SiB2 is a superconductor with a transition temperature (T_{\text{c}}) of 5.8 K. The magnetization versus magnetic field (M--H) curve shows the typical type-II superconducting behavior. The estimated lower critical field H_{\text{c1}}(0) and upper critical field H_{\text{c2}}(0) are about 120 and 5200 Oe, respectively. The penetration depth \lambda and coherence length \xi are calculated to be approximately 210 and 25 nm, respectively, using Ginzburg--Landau (GL) equations. The estimated Sommerfeld coefficient \gamma_{\text{N}} is 12.8 mJ/(mol K2). The normalized specific heat jump \Delta C/\gamma_{\text{N}}T_{\text{c}} is estimated to be about 1.49, which is near the value predicted by the BCS theory in the weak-coupling limit, i.e., \Delta C/\gamma_{\text{N}}T_{\text{c}} = 1.43. This finding indicates that super conductivity in W5SiB2 exists within the week-coupling regime.
2011-02-15