Flux penetration in spheroid samples-critical state model with field-dependent critical current density

Abstract

We present the results of a calculation, within the framework of Bean's critical state model, of the magnetization curves for a hard superconductor sample in the shape of a spheroid. The formalism allows a general field dependence of the critical current density J_c. We present numerical results for J_c decaying exponentially with field. Some main experimental features are reproduced and detailed tests can be made with experiments on thin films and platelet-shaped single crystals.