Simulation of the intergranular magnetization of (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+x superconductors by using Josephson junction arrays

In this paper we present a numerical simulation study of the intergranular magnetization of (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+x superconductors. The intergranular-current system was modelled as a two-dimensional Josephson junction array, which consists of superconducting grains connected via overdamped, narrow Josephson weak links. The simulations cover magnetic-flux distribution and magnetic-hysteresis studies, including relaxation effects due to thermal fluctuations in the junctions. Special attention was paid to the influence of intergranular defects on the array magnetization and intergranular flux pinning, with the motivation to find model parameters which fit to the experimental behavior of (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+x. A correspondence with the experimental results [Paasi et al., Physica C 259 (1996) 1) (previous paper)] required that there was an intergranular defect of the μm order located in the middle of the four grains of an array mesh. Such a defect could act as a strong pinning center for intergranular flux.