Fluctuation-Induced Conductivity of Polycrystalline (Ho-Ce)Ba 2 Cu 3 O 7-δ Superconductor

Author: Kurelo Anderson  

Publisher: Springer Publishing Company

ISSN: 0103-9733

Source: Brazilian Journal of Physics, Vol.41, Iss.1, 2011-05, pp. : 1-6

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Abstract

We report on systematic conductivity fluctuation measurements on samples of Ho1 − xCexBa2Cu3O7 − δ with x = 0.00, 0.05, and 0.10. The samples were produced by a standard solid-state reaction method, and the microstructure was analyzed by X-ray diffraction. To identify power-law divergences of the conductivity, the results were analyzed in terms of the temperature derivative of the resistivity /dT and with the logarithmic derivative of the conductivity with respect to temperature − dln (Δσ)/dT. It was observed that the critical temperature decreases and that the transition width increases with increasing Ce doping. The data showed the occurrence of a two-stage transition besides the pairing transition splitting, associated with Ce doping and related with the occurrence of a phase separation. Above the critical temperature, the Gaussian and critical regimes were observed. On approaching the zero resistance state, our results showed a power-law behavior that corresponds to a phase transition from a paracoherent to a coherent state of the granular array.