EFFECT OF COLUMNAR DEFECTS ON THE J(C) ANISOTROPY OF YBA2CU3O7-DELTA THIN-FILMS AND YBA2CU3O7-DELTA PRBA2CU3O7-DELTA MULTILAYERS/

Epitaxial YBa2Cu3O7-delta thin films (YBCO) and YBa2Cu3O7-delta/PrBa2C u3-delta multilayers (Y/Pr) were irradiated with high-energy heavy ion s (770 Mev Pb-208) under various directions phi relative to the c-axis . The irradiation resulted in columnar defects tilted by phi from the c-axis. The angular dependence of their pinning activity was studied b y measuring the anisotropy of the critical current density. The J(c)(B , T, I) behavior of the irradiated YBCO thin films showed an additiona l peak, which exceeds the intrinsic pinning peak, exactly at the irrad iation direction. The Y/Pr multilayers, however, showed an isotropic J (c)-enhancement by a factor of 5 without an additional structure in th e J(c)(B, T, I) curve.