X-RAY-ABSORPTION MULTIPLE-SCATTERING STUDY OF ANGLE DISTRIBUTION IN HIGH-TC SUPERCONDUCTORS

A new method, designed to perform data-analysis of X-ray absorption data and previously applied to molecular cases, has been used to investigate high-T(c) superconductors for the first time. This method includes properly multiple-scattering contributions to the EXAFS spectra. In this way, it is possible to derive unconventional structural information such as the angle distributions associated with the main scattering paths. We have analyzed well-known superconducting samples such as YBa2Cu3O almost-equal-to 7 and Bi2Sr2CaCu2O almost-equal-to 8. In both cases, quantitative local structural information has been extracted from Cu K-edge EXAFS spectra by using a fitting procedure which performs the average of the multiple-scattering contributions. The dominant signal due to the in-plane Cu-0-Cu angle distribution has been accurately studied taking proper account of the multiple-scattering signals due to the quasi-linear configurations. A good agreement with diffraction results has been found. This application shows the capability of EXAFS to measure the local Cu-O-Cu angle distribution in this class of compounds.