Transport critical current in granular samples under high magnetic fields

A theoretical model for the magnetic field dependence of the transport crit ical current density in granular superconductors (J(c)(B)) is proposed. In this model the transport critical current density is controlled by the weak -links (WLs) network present in the samples, and also, the influence of the field penetrating the grains is considered. Our results depend on the micr ostructure via the parameters of the WL distribution, and seems to reproduc e the overall experimental data reported in the literature. A characteristi c field is found from our study that characterizes the J(c)(B) dependence. Different field regimes are considered leading to simple expressions for J( c)(B). (C) 2001 Elsevier Science B.V. All rights reserved.