Transport and thermodynamic properties of a sintered pellet were measured to determine the characteristic critical magnetic fields and critical current densities. Both resistive transition and magnetization data gave similar values for the upper critical field, HC2, with magnetization data giving dHC2/dT = 0.44T/K at the transition temperature of 40.2K. Close to the transition temperature, magnetization curves were thermodynamically reversible, but at low temperatures the trapped flux could be of the order of 1T. The value of dHC/dT at TC was estimated to be about 12mT/K, a value similar to classical superconductors such as Sn. Hence, the Ginzburg-Landau parameter was approximately 26. Estimates of the critical supercurrent density using hysteresis loops and the Bean model, gave critical current densities of the order of 105A/cm2. Hence the supercurrent coupling through the grain boundaries was comparable to intermetallics like Nb3Sn.

Thermodynamic and Transport Properties of Superconducting MgB2. D.K.Finnemore, J.E.Ostenson, S.L.Budko, G.Lapertot, P.C.Canfield: Physical Review Letters, 2001, 86[11], 2420-2