NEGATIVE-MU VORTEX DYNAMICS IN HIGH-T-C SUPERCONDUCTING FILMS

Using a thermally activated vortex motion model with an activation ene rgy U(j)=(U-c/mu)[j(c)/j)(mu)-1] in which U-c, mu and j(c) are field a nd temperature dependent we analyse both flux-creep data and current-v oltage characteristics on the same footing. This analysis reveals the occurrence of negative-mu vortex dynamics in highly anisotropic superc onductors such as Tl2Ba2CaCu2O8 or Bi2Sr2CaCu2O8 above a characteristi c magnetic field. This is attributed to a dimensional cross-over and p lastic creep.