Intermittent propagation of magnetic flux in superconductors.

Regular arrays of planar defects can be introduced in superconducting YBa2Cu3O7 thin films by depositing them on tilted substrates. This results in anisotropy of critical currents flowing in the plane of the film. At optimal tilt angles a substantial increase of the critical currents flowing in both directions, i.e. along and across the planar defects, has been observed. However, the artificially introduced defects also have a dramatic effect on dynamics of the flux propagation: it becomes intermittent. Previously we observed intermittent flux penetration in MgB2 thin films with thermo-magnetic instability, where such flux jumps trigger giant magnetic avalanches. In this report we present results of a real time magneto-optical visualization of the intermittent flux motion in YBCO and discuss possible consequences for its thermo-magnetic stability.