CRITICAL CURRENTS IN POLYCRYSTALLINE YBA2CU3O7-X

In this paper the critical density for a polycrystalline sample is calculated assuming a model of weakly coupled superconducting grains and the influence of grain size on the maximum tunnelling current is investigated. In addition the Josephson vortices are shown to be bound by the pinning force inherent to the magnetic behaviour of the weak link between grains. The intergrain critical current density is derived as a function of field and temperature and the results of the calculations are illustrated with reference to experimental data from a.c. susceptibility and low field magnetization measurements. © 1990.