VORTEX DYNAMICS IN BI2SR2CACU2O8-THIN FILMS IN THE PRESENCE OF COLUMNAR DEFECTS

With heavy ion irradiation we create continuous amorphous columnar def ects in Bi2Sr2CaCu2O7-thin films. With regard to a reliable comparison of irradiation effects three of four identical striplines on the same samples were exposed to different irradiation procedures. We performe d irradiations as well parallel as under different angles with respect to the film <(c)over right arrow -axis>. Beside an enlarged normal st ate resistivity after irradiation the films suffer a T-c-reduction pro portional to the volume of the damaged material. The activation energy ascertained from resistive transitions shows best enhancement for mag netic field values close to the matching field. Measurements of the tr ansport critical current density, the activation energy and the irreve rsibility field in different field orientations show no anisotropic fl ux pinning due to the induced columnar defects. This cast be explained by the two dimensional behaviour of the Bi2Sr2CaCu2O8-thin films.