FLUX NOISE, VORTEX-GLASS TRANSITION, AND IRREVERSIBILITY LINE IN CERAMIC TL2BA2CA2CU3O10-DELTA HIGH-T-C SUPERCONDUCTORS

The flux noise and irreversibility line in ceramic Tl2Ba2Ca2Cu3O10-delta high-T-c superconductors have been measured by a DC SQUID, and the vortex glass transition has been detected by the standard four-terminal I vs. V measurement. In the low magnetic field region (0<H<1000 Oe), it is found that the flux-noise peak coincides with the vortex glass phase transition temperature T-g. However, there is an obvious difference in temperature between the irreversibility temperature T-irr, and T-g. T-irr is always higher than T-g. Our experimental results indicate that the irreversibility line is a dynamical boundary rather than a phase boundary.