Flux creep characteristics of c-axis-oriented Bi2Sr2CaCu2Ox thin films
grown by the method of electron beam evaporation of stoichiometric ta
rget and subsequent annealing have been investigated in the absence of
external magnetic field. A decrease of the pinning potential with dec
reasing temperature is obtained from I-V curves. This result is explai
ned by the presence of the spatially nonlinear pinning potential.