INFLUENCE OF THE MAGNETIC-FIELD SWEEP RATE ON FLUX-CREEP IN HIGHLY TEXTURED THIN-FILM OF YBA2CU3O7-DELTA

We investigated the influence of the field sweep rate on the magnetic relaxation and the critical current density of a highly textured thin films of YBa2Cu3O7-delta at different temperatures and fields parallel to the c-axis. We find that the actual M versus In t relationship can be deduced experimentally by a transformation of the form t-->t+tau+t au(vs) in which tau is a transient time proportional to Rx(dH/dr)(-1), tau(vs), the time constant of the magnetometer (similar to 0.25 s) an d R the effective radius of the superconducting him averaged along the a-b planes. As a result. all the relaxation curves collapse into a si ngle-master one that is independent of the experimental conditions. Th e parameter tau obeys approximately the relationship tau xdH/dt approx imate to 2 Oe in the range T<30 K and depends on the film thickness. T he resulting J versus In t relationship deviates from linearity for al l the explored temperatures and fields.