Analysis of thermo-magnetic fluctuations above the glass-transition temperature in Bi 1.6Pb 0.5Sr 2− xEu xCa 1.1Cu 2.1O 8+ δ (0.000 ≤ x ≤ 0.180) system

Abstract

The resistivity of Bi 1.6Pb 0.5Sr 2− x Eu x Ca 1.1Cu 2.1O 8+ 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 [ T g], magnetic field dependent activation energy [ U 0( B)] and the temperature and magnetic field dependent activation energy [ U 0( 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 ( T C), 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.