Abstract
The temperature dependence of AC susceptibility of polycrystalline YBa 2Cu 3O y thin film and (Bi,Pb) 2Sr 2Ca 2Cu 3O y bulk samples were measured as a function of frequency and AC field amplitude. Analysis of the temperature dependence of the AC susceptibility near the transition temperature ( T c) has been done employing Bean's critical state model. The observed variation of intergranular critical current densities ( J c) with temperature indicates that the intergrain coupling in these samples can be modeled in terms of superconductor–normal metal–superconductor junctions. The frequency effect on AC susceptibility was also measured. As the frequency increases, the peak temperature ( T p) shifts to higher temperature. This effect can be interpreted in terms of flux creep. The field dependence of activation energy obtained from the Arrhenius plot for the frequency ( f) and ( T p), can be described as U( H AC)∼ H AC − β for both samples.
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