Thermodynamic and transport properties of superconducting Mg10B2

Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB2 superconductor have been measured to determine the characteristic critical magnetic fields and critical current densities. Bath resistive transition and magnetization data give similar values of the upper critical field, H-c2, with magnetization data giving dH(c2)/dT = 0.44 T/K at the transition temperature of T-c = 40.2 K. Close to the transition temperature, magnetization curves are thermodynamically reversible, but at low temperatures the trapped flux can be on the order of 1 T. The value of dH(c)/dT at T-c is estimated to be about 12 mT/K, a value similar to classical superconductors like Sn. Hence, the Ginzburg-Landau parameter kappa similar to 26. Estimates of the critical supercurrent density, J(c), using hysteresis loops and the Bean model, give critical current densities an the order or 10(5) A/cm(2). Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics Like Nb3Sn.