Influence of the anisotropy in the c-axis resistivity measurements of high-T-c superconductors

The cross-measurement configuration, commonly used in the determination of the c-axis resistivity was the matter of our theoretical analysis. We obtai ned an analytical expression for the measured resistivity which depends on a 'effective anisotropy' factor, identified here as Gamma, and takes into a ccount the non-homogeneous current distribution into the sample. We showed that the best experimental results are obtained for superconductor samples with the largest Gamma. In particular, for samples with Gamma > 1, the dist ance between the voltage contacts and the current ones should be a third of the length of the sample in order to obtain the real rho(c) and to avoid t he use of other complicated experimental set-up. (C) 1999 Published by Else vier Science B.V. All rights reserved.