CHARACTERISTIC EXPONENTS NEAR VORTEX-GLASS TEMPERATURE IN GDBA2CA3CU7-DELTA FILM

The I-V curves of GdBa2Ca3Cu7-delta film were measured at temperatures near the vortex-glass transition temperature T-g. For T < T-g the tem perature dependence of the glassy exponent mu, the collective pinning energy U-c and the critical current density J(c) are derived from I-V curves. It is found that mu changes with temperature and field. The ex perimental results can be described with vortex-glass or collective pi nning and creep theory. For T > T-g, we determined the critical expone nts by scaling the nonlinear I-V curves. These exponents are consisten t with values expected for freezing into a superconducting vortex-glas s phase. (C) 1997 Elsevier Science B.V.