VORTEX-ACTIVATION ENERGY AND CRITICAL CURRENTS OF Y1BA2CU3O7-DELTA THIN-FILMS CONTAINING SCREW DISLOCATIONS

Torque-magnetometry was performed on a Y1Ba2Cu3O7-delta thin film containing screw dislocations. By varying the sweep-rate of the applied magnetic field, the activation energy of the flux-lines U(j,B,T) was investigated. Assuming a linear or logarithmic current dependence for U(j), the pinning energy U(c)(B,T) and critical current density j(c) could be determined. For both current dependences, U(c)(B,T) was found to increase strongly at fields less-than-or-equal-to 0.25 T. This behaviour could be related to flux-pinning caused by screw- and edge dislocations. For fields applied at different angles, the measured magnetization was dependent on the perpendicular component of the applied magnetic field, in agreement with the behaviour expected for a thin film with a thickness d below the penetration depth lambda.