STRUCTURES IN SUPERCONDUCTING YBA2CU3O7-DELTA THIN-FILMS INVESTIGATEDBY MAGNETOOPTIC TECHNIQUE

Using a reflection magneto-optic technique we have investigated natura l inhomogeneities and artificial structures in YBCO thin films exposed to an external magnetic field. The artificial structures were mechani cally scratched by scanning a diamond tip with different loading over the film surface. Alternatively planar structures with reduced oxygen content could be patterned by heating the YBCO film with a focused las er beam in nitrogen atmosphere. Depending on the laser annealing param eters different screening properties concerning the applied magnetic f ield could be achieved. As a magneto-optically active layer we used Eu S films evaporated on glass as well as bismuth- and gallium-doped lute tium-iron-garnet films grown onto (111) oriented gadolinium-gallium-ga rnet substrates by liquid phase epitaxy. In contrast to measurements w ith EuS films that show only weak fara day rotation for temperatures h igher than 20 K the magneto-optic studies have been expanded to about 60 K by using the garnet films.