Magnetic Properties of a Granular Superconductor
We investigate the magnetic properties of the disordered and frustrated XY-model to model weakly coupled superconducting grains in a magnetic field. Extending the mean field approximation to include the induced field, we treat the magnetic field self- consistently and derive the internal field distribution. Furthermore we calculate numerically the critical line in the (H,T)-phase diagram, providing evidence for the experimentally observed H 2/3 behavior. Moreover we study the nonequilibrium properties in terms of the relaxation of the excess magnetization following a field jump. Our numerical results exhibit the aging effect previously found in spin glasses and in high temperature superconductors.
KeywordsSpin Glass Critical Line Josephson Current Thermoremanent Magnetization Positive Definite Hermitian Matrix
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