Flux pinning by columnar defects in Bi2Sr2CaCu2O8-thin films

In Bi2Sr2CaCu2O8-thin films continuous amorphous columnar defects were created by heavy ion irradiation. Three of four identical striplines on the same sample were irradiated in a different way which includes irradiations under different angles with respect to the film (c) over right arrow-axis. After irradiation the normal state resistivity is enlarged and the films exhibit a reduction of re proportional to the volume of the damaged material. Furthermore the activation energy for flux movement shows an enhancement which is best for magnetic fields close to the matching field. Measurements of the transport critical current density, the activation energy and the irreversibility field in dependence of the angle between magnetic field and the film (c) over right arrow-axis show no anisotropic pinning due to the induced columnar defects. This can be related to the intrinsic two-dimensionality of Bi2Sr2CaCu2O8.