X-ray absorption study of the CuO2 plane in Nd2-xCexCuO4-delta

The local structure of the CuO2 planes in Nd2-xCexCuO4-delta (x = 0, 0.15; delta similar to 0.01) has been examined by temperature-dependent Cu K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. Three diffe rent Cu-O distances can be extracted up to at least 100 K, indicating that the atomic structure of the CuO2 planes deviates from the T' structure much more than it was expected. Positions of the displaced O1 atoms for x = 0.1 5 were obtained from comparative analysis of the experimental and calculate d polarized Cu K-edge X-ray absorption near-edge structure, taking into acc ount many-body excitations in the CuO2 planes. (C) 2000 Elsevier Science B. V. All rights reserved.