CURRENT-DENSITY INHOMOGENEITY THROUGHOUT THE THICKNESS OF SUPERCONDUCTING FILMS AND ITS EFFECT ON THEIR IRREVERSIBLE MAGNETIC PROPERTIES

We calculate the distribution of the current density j in superconducting films along the direction of an external field applied perpendicular to the film plane. Our analysis reveals that in the presence of bulk pinning j is inhomogeneous on a length scale of the order of the intervortex distance. This inhomogeneity is significantly enhanced in the presence of surface pinning. We introduce a critical state model, which takes into account the current-density variations throughout the film thickness, and show how these variations give rise to the experimentally observed thickness dependence of j and magnetic relaxation rate. @S0163-1829~98!03121-X#