FLUCTUATION CONDUCTIVITY IN MELT-TEXTURED YBa2Cu3O7-δ

Abstract

Systematic measurements of the in-plane and out-of-plane fluctuations magnetoconductivity in a melt-textured sample of YBa 2 Cu 3 O 7-δ are presented. The experiments were performed in fields ranging from 0.02 T to 5 T applied perpendicular to CuO 2 atomic (ab) planes. The measurements of the in-plane fluctuations were performed in zero applied field. The method of analysis is based on the determination of the quantity [Formula: see text], where Δσ = σ - σR is the fluctuation conductivity. In the normal phase, contributions from Gaussian regimes are clearly evidenced. These regimes are unstable regarding the application of magnetic fields perpendicular to the ab plane. Below TC, in approaching the zero resistance state, our results show a power-law behavior, that is indicative of a phase transition from paracoherent to a coherent state of the granular array.