Analysis of thermo-magnetic fluctuations above the glass-transition temperature in Bi1.6Pb0.5Sr2−xEuxCa1.1Cu2.1O8+δ (0.000 ≤ x ≤ 0.180) system

The resistivity of Bi1.6Pb0.5Sr2−xEuxCa1.1Cu2.1O8+δ (0.000 ≤ x ≤ 0.180) superconductor has been measured as a function of temperature and magnetic field. The resistivity shows a glassy behavior even at higher temperatures and magnetic fields for the Eu-doped samples as compared with the Eu free sample. The values of glass-transition temperature [Tg], magnetic field dependent activation energy [U0(B)] and the temperature and magnetic field dependent activation energy [U0(B,T)] are found to be maximum for optimal doping levels (x = 0.135) which shows that the flux lines are effectively pinned in this sample. Also for temperatures below the superconducting transition temperature (TC), a scaling of measured resistivity curves in magnetic field (B = 0.4 and 0.8 T) is obtained and this scaling is quite useful for better understanding of the behavior of the flux vortices in high temperature superconductors.

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