Anisotropic critical-state model of type-II superconducting slabs

Abstract

We introduce a critical-state model incorporating the anisotropy of flux-line pinning to analyze the critical states developing in an anisotropic biaxial superconducting slab exposed to a uniform perpendicular magnetic field and to two crossed in-plane magnetic fields which are applied successively. The theory is an extension of the anisotropic collective pinning theory developed by Mikitik and Brandt. The anisotropic flux-line pinning enters into the critical states by generating the angular dependence of the critical current density and by deviating the direction of the electric field from the current in the plane perpendicular to the vortex line. Compared to the isotropic case, the anisotropic flux pinning strongly influences the magnetic response in the slab. We also apply the critical-state model to predict the underlying physical phenomena of a field-cooled slab in a rotating magnetic field.