Equilibrium behaviour and vortex pinning in MgB2 single crystals

Magnetization isotherms for MgB2 single crystal platelets, measured along the two principal crystalline orientations, have been fitted to theoretical treatments, which include a phenomenological model for the constitutional equilibrium Be(H) behaviour based on the two-band nature of the MgB2 system. Self-consistent results are obtained for bulk Hc1(T) (c-axis and ab-plane) and Hc2(T) (c-axis only), and the G-L parameter κ in various regimes of the B-T plane for the two orientations. The critical current density, for both orientations, is found to be given by Jc(B)∝(1/B)exp(-B3/2)