FLUX CREEP IN C-AXIS ORIENTED EPITAXIAL YBA2CU3O7 THIN-FILM

A systematic study of the flux creep behavior has been carried out for c-axis oriented epitaxial YBa2Cu3O7 thin films based on the Anderson and Kim flux creep model. In a wide magnetic field (H) range (0 to 12 T) and temperature (T) range (10 to 82 K), the behavior of the critical current density J(c), the flux bundle (size upsilon-d and jump distance l) and resistive transiton broadening DELTA-T(c) have been investigated. It is found that J(c)(H, T) fairly well obeys the frame of flux creep model in the above temperature range; in a certain low-field region (less-than-or-similar-to 1 T), a relation of upsilon-d proportional H-1 is found; in the high (H, T) region, upsilon-d(l) shows an anomalous behavior which is discused in terms of the decomposition of the flux bundle. It is also found that the relation of DELTA-T(c) porportional H-2/H-3 exists in all field orientation against the c-axis, but the slope of DELTA-T(c) versus H-2/H-3 depends strongly on orientation.