Effect of columnar defects in YBa2Cu3O7−x ramp-edge Josephson junctions

We investigated the transport properties in YBa2Cu3O7-x (YBCO) ramp-edge Josephson junctions before and after 1.3 GeV Pb-ion irradiation. The barrier of the junctions was formed by structural modification of the ramp-edge surface of the YBCO base electrode. After a dose of similar to 2x10(10) Pb ions/cm(2), both critical current and normal resistance of the junctions increased by similar to 30% and 10%, respectively, except near the transition temperature. We interpret such an enhancement of the critical current as a result of impeding Josephson vortex motion by pinned magnetic flux in the electrodes. (C) 2000 American Institute of Physics. [S0003-6951(00)01846-5].