Simulation and study of the percolation effect in the magnetic susceptibility of high-temperature superconducting composites

A simple model is proposed to analyze the relationship between susceptibili ty and composition in superconducting composites. The model is based on a r andom distribution of superconducting and nonsuperconducting phases and on the occurrence of shielding when a nonsuperconducting area is encapsulated by superconducting material. A three-dimensional simulation based on percol ation theory is in agreement with our experimental data on a series of MgO- superconductor composites. A predicted percolation effect was observed and a maximum in shielding efficiency was determined.