VORTEX PLASTIC CREEP IN A SUPERCONDUCTING CRYSTAL OF TL-2223

The dissipation in the mixed state of a Tl2Ba2Ca2Cu3O10 (Tl-2223) crys tal was studied by an analysis of the DC relaxation and that of the fr equency dependence of the AC susceptibility. Near the irreversibility line, the field dependence of the activation energy at zero current li mit evidences the plastic nature of the vortex movement mediated by in dividual vortex loops. At lower temperatures, the data are analysed in a current dependent activation energy U(J) framework. The data are an alysed in the model proposed by Abulafia et al. in U-0(1-(J/J(0))(1/2) ) which predicts a non divergent energy barrier at zero current. The a nalysis of the magnetic field dependence of U, has shown that the plas tic model used in the region of the irreversibility line can account f or the observations. In this system, no elastic collective creep was o bserved in the domain that we have explored. (C) 1998 Elsevier Science B.V. All rights reserved.