Magnetic, transport and high-pressure properties of a W7Re13B superconducting compound

In this report we present experimental and theoretical investigations of the properties of the recently discovered W7Re13B superconductor. This compound is synthesized by means of inductive melting and contains a pure phase with a sharp superconducting transition at T-c = 7.22 K. The superconductor exhibits type-II behaviour with reversible magnetic properties in a large part of the H-T diagram. The irreversibility line with the irreversibility field mu H-0(irr)(0) equal to 2 T is well separated from the upper critical field. The values of lower mu H-0(c1)(0) and upper mu H-0(c2)(0) critical fields are equal to 8.8 mT and 11.8 T, respectively. These values correspond to penetration depth lambda, coherence length xi and Ginzburg-Landau coefficient kappa equal to 2675 angstrom, 52 angstrom and 51, respectively. The critical current density J(c) is low and equal to 4.9 kA cm(-2) at zero magnetic field and at 2 K. The effect of pressure on superconducting properties is almost negligible, probably due to the low compressibility of this compound. The pressure coefficient dT(c)/dP is negative and equal to -0.037 K GPa(-1). The XPS spectrum and numerical calculations confirm that the main contributions to the density of states at the Fermi level come from W(5d) and Re(5d) states.