AC SUSCEPTIBILITY RESPONSE AND CRITICAL-CURRENT DENSITY OF A NOMINAL HG1-XPBXBA2CA2CU3O8-STATE MODELS(DELTA SUPERCONDUCTOR FOR DIFFERENT CRITICAL)

Various critical state models used to estimate the critical current de nsity J(c) of the granular superconductor were studied. Results of suc h estimation were compared with the results from the AC susceptibility measurements of the Hg0.69Pb0.31Ba2Ca2Cu3O8+delta sample. By using le ast-square analyses, it is found that all these critical state models are generally agreed with the experimental data quite well. The theore tical results of J(c) for different critical state models were discuss ed. In order to estimate the critical current density J(c), the parame ters B-o and B-p involved in the critical current density expression w ere extracted by using a specific technique. It was shown that the J(c ) vs T curves for different critical state models are close one to ano ther within the high temperature range close to T-c of the superconduc tor.