Magnetic behavior of granular high-Tc superconductors in the weak-link regime

The spatial distribution of the magnetic induction B in Y–Ba–Cu–O high-temperature superconducting ceramics in an external magnetic field of small magnitude is investigated theoretically. The applied phenomenological theory covers the weak-link regime of the superconductor and takes into account the intergranular currents together with intragranular currents, using an effective magnetic permeability μ<1. Besides, the material equation that relates the electric field E with the intergranular current density J is based on the Bean critical-state model for multicomponent situations. We calculate the evolution of the profiles of the magnetic induction B in a granular superconducting plate in an external magnetic field Hy (parallel to its plane), which is switched on and then switched off. Later, the superconducting plate was subjected to a crossed external magnetic field Hz. The profiles corresponding to the residual magnetic induction are analyzed and compared with available experimental results.