Comparison of the pinning and the bulk currents in the critical state of a type-II superconductor

The bulk current density distribution in the critical state of a type-II superconductor is studied for different pinning strengths and external magnetic fields. The calculations were made within the extended critical slate model for a three-axis ellipsoid, taking into account the equilibrium vortex lattice magnetization caused by the vortex interaction. It is shown that the average current density, J(av), could be considerably different from the critical pinning current density, J(c), for the magnetic fields not much larger than the lower critical field H-cl. The difference between J(av) and J(c) result in additional curvature of the local magnetic field profiles and modifies the total moment of the sample which might be important for the analysis of various magnetization experiments. (C) 1998 Elsevier Science B.V.