FLUCTUATION-INDUCED CONDUCTIVITY OF POLYCRYSTALLINE Er1-xCexBa2Cu3O7-δ SUPERCONDUCTOR

Abstract

A detailed study of the effect caused by the partial substitution of Er by Ce on fluctuation conductivity of the Er 1-x Ce x Ba 2 Cu 3 O 7-δ; 0 ≤ x ≤ 0.10; is presented. The combined experimental results of structural and electrical measurements indicate that Ce substitutes Er for x ≤ 0.10 with no significant structural distortions. However, there is suppression of the superconducting state with zero-resistance state at temperatures ≥ 86.3 K. The results were analyzed in terms of the temperature derivative of the resistivity and the logarithmic temperature derivative of the conductivity to identify power-law divergences of the conductivity. The data revealed the occurrence of a two-stage intragranular-intergranular transition. Above the critical temperature, the Gaussian and critical regimes were observed. Also, from the critical exponents analysis, we observed a splitting of the pairing transition for Ce -doped samples, suggesting the occurrence of a phase separation. 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 and which does not depend on Ce doping.