Excess conductivity studies in the paracoherence region of Bi-Sr-Ca-Cu-O superconductors

Abstract

The temperature variation of resistivity of several Samples of 85 K and 110 K superconductors of BiSrCaCuO system prepaed under different conditions was analysed in terms of excess conductivity due to phase fluctuations in the paracoherence region. The average values of estimated excess conductivity critical exponent (γ) for the 85 K and 110 K superconductors are respectively 2.55 and 2.75. The paracoherence to coherence transition in a granular superconductor is compared to the paramagnetic to ferromagnetic transition of 3D XY ferromagnets. The γ values obtained for these superconducting samples differ from the predicted susceptibility critical exponent value for the pure 3D XY ferromagnets. However, the obtained γ values are comparable to the susceptibility critical exponent of the disordered 3D Heisenberg ferromagnet system. © 1995.