Abstract :
AC susceptibility has been measured simultaneously in three different regions of YBCO ceramic samples, in the presence of a strong thermal gradient, in order to pinpoint local perturbation. A local step-like perturbation, applied in addition to the monotonic temperature decrease, produces a jump-like increase of the coherent region. The superconducting regions enlarge much faster than the propagation of the thermal waves. We suggest that the adiabatic magnetic flux jump reflect the creation of new coherent domains over Tc by stimulated correlation of the order parameter phase.
