Thermodynamic and transport properties of superconducting (MgB2)-B-10

Transport and thermodynamic properties of a sintered pellet of the newly di scovered MgB2 superconductor have been measured to determine the characteri stic critical magnetic fields and critical current densities. Bath resistiv e transition and magnetization data give similar values of the upper critic al 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 tempera tures 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 superco nductors like Sn. Hence, the Ginzburg-Landau parameter kappa similar to 26. Estimates of the critical supercurrent density, J(c), using hysteresis loo ps 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.