Magneto-optical observation of the influence of an artificial periodic magnetic pattern on the pinning of a YBa2Cu3O7-delta thin film

In a recent paper [1], it has been shown from transport measurements that a rtificial reversible pinning can be created by the application of a magneti c tape on the surface of a thin superconducting film. We study the influence of a periodic array of magnetic stripes, generated f rom a signal pre-recorded on a magnetic tape, on the pinning of vortices. W ith our high resolution magneto-optical technique [2], we visualize in two dimensions the penetration of the flux in a thin YBa2Cu3O7-delta film parti ally covered by such a magnetic tape. In particular, we investigate the evo lution of flux entry in the superconducting strip under and next to the mag netic tape. We present results obtained for various temperatures and variou s applied fields.