Resistive transition and fluctuations of the conductivity in YBa2Cu3O7, EuBa2Cu3O7 and GdBa2Cu3O7 superconductors: Effect of inhomogeneities

✍ Scribed by P. Pureur; J. Schaf; M.A. Gusm≈ao; J.V. Kunzler

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 761 KB
• Volume: 176
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(91)90038-z

✦ Synopsis

Systematic resistivity measurements in polycrystalline samples of the high-To oxide superconductors RBa2Cu307 (R = Y, Eu, Gd) are performed with several (low) current densities. Special attention is devoted to the temperature range close to the superconducting transition. The data allows the determination of temperature derivatives of the resistivity, which reveal the occurrence of a two-step transition. This feature is typical of a granular system. Two scaling regimes for the fluctuation conductivity are also identified. Near the temperature where the grains become superconducting, the enhancement of the conductivity follows a power law with sample dependent exponents. Analysis of this result on the basis of the Aslamazov-Larkin theory indicates that a fractal topology might be adequate to describe the inhomogeneous superconducting state. In the second scaling regime, near the zeroresistance temperature, an apparently universal exponent i's observed.