Vortex-glass-liquid transition and critical current density in Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ superconductors

We have investigated I-V characteristics in epitaxial Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/, thin films and Ag-sheathed tapes in magnetic fields applied parallel to the c-axis, and observed a transition from the vortex-liquid phase characterized by finite linear resistivity /spl rho//sub lin/=(E/J)/sub J/spl rarr/0/=constant, to the vortex-glass phase with vanishing linear resistivity. The transition shows quasi-2D nature and a power-law relation E/spl sim/J/sup z+1//spl ap/J/sup 6.5/ is observed at the transition temperature T/sub g/, while E/spl sim/J/sup z+1//2/spl ap/J/sup 3/ is observed in YBa/sub 2/Cu/sub 3/O/sub 7/ at T=T/sub g/, where z is a critical exponent. The importance of the vortex-glass transition in applied superconductivity is discussed.<
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