Artificial reversible and programmable magnetic pinning for high-T_c superconducting thin films

A new technique for creating artificial pinning structures in thin superconducting films by means of applying a magnetic tape containing a pre-recorded signal to the sample surface has been proposed and tested experimentally with YBaCuO high-T_c thin films. The technique allows reversible introduction of controllable potential profiles for vortices in thin film superconductors. It has been demonstrated that application of a tape containing a pre-recorded periodic signal is capable of increasing the critical current of a thin film strip. Periodic pinning conditions result in the appearances of commensurability effects revealed by the observation of a periodic component in the voltage recorded at a constant current bias as a function of applied magnetic field. Periodic potential relief enforces coherent flow of vortices in wide and short macrobridges and leads to the appearance of constant current steps in I-V curves. It has been found that step voltages scale with the inverse of the magnetic period, in agreement with a modified Josephson relation.