Double critical-state model for the weak-link regime of granular high-Tc superconductors

Abstract The phenomenological double critical-state model, which uses critical values for the components of the current-density both perpendicular and parallel to the local magnetic induction B , is applied to tubes of granular high- T c superconductors in the presence of axial and azimuthal magnetic fields. We develop a theory valid for the weak-link regime of these superconductors. In this theory not only intergranular but also intragranular currents are taken into account. The behavior of the magnetic induction inside the wall of a superconducting tube cooled below the critical temperature in the axial magnetic field and, later, subjected to an increasing azimuthal field, is analyzed. Our theoretical results are compared with the experiment.