E. Sheriff | Searcharxiv

arXiv1998

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 order the inter vortex distance. This inhomogeneity is significantly enhanced in the presence of surface pinning. We introduce new 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.

cond-mat.supr-con↗

arXiv1996

Irreversible magnetization in thin YBCO films rotated in external magnetic field

The magnetization M of a thin YBaCuO film is measured as a function of the angle $θ$ between the applied field H and the c-axis. For fields above the first critical field, but below the Bean's field for first penetration H*, M is symmetric with respect to $θ=π$ and the magnetization curves for forward and backward rotation coincide. For H>H* the curves are asymmetric and they do not coincide. These phenomena have a simple explanation in the framework of the Bean critical state model.

supr-con↗