CuOCu in-plane angle distribution in layered superconductors probed by EXAFS

Abstract

Accurate Cu K-edge EXAFS spectra of doped and undoped lanthanum cuprates, collected in the temperature range 10–300 K, are analyzed taking proper account of the strong multiple-scattering (MS) signal found in these layered compounds (GNXAS method). A double-electron excitation [1s3p] channel has been evidenced and considered in the data treatment. CuO and Cu(La,Sr/Ba) distance distributions have been measured, as well as the distribution of the CuOCu in-plane quasi-linear three-body configurations. In the latter case, the strong MS signal allowed an accurate study of the bond-angle distribution, associated with the buckling of the CuO 2 planes. A detailed analysis of the statistical errors on the structural parameters has been performed, showing the reliability of the short-range structural refinement. The results are found to be consistent with previous diffraction and infrared data. Different features of the CuOCu distribution in superconducting and non-superconducting materials are discussed.