PENETRATION DEPTH OF HIGH-TC GRANULAR SUPERCONDUCTORS IN THE LOW-FIELD REVERSIBLE REGIME

A superconducting granular sample is described by a network of Josephson junctions and inductances associated with the superconducting current branches. By this picture a model of concentric current shells for simulating magnetic field penetration is developed. An analytical calculation of the penetration depth in the low-field reversible regime is performed taking explicitly into account fluxoid quantization for any superconducting loop in the network. The thermodynamic and the experimental reversibility range is finally discussed in terms of the inductive coupling strength among the junctions.