Anomalous x-ray diffuse scattering of short-range order in Nd2−xCexCuO4−y

Abstract

Anomalous x-ray diffuse scattering is used to study the short-range order (SRO) and lattice distortions in the electron-type superconductor, Nd1.85Ce0.15CuO4−y. The intensity measurements were made at two energies below the Ce LIII absorption edge; the difference data greatly simplified the analysis to involve only atom pairs including Ce. The data sets were analyzed using a kinematic diffraction equation expanded up to the second order in atomic displacements. The fitted SRO parameters indicate the formation of Ce-Ce atom pairs along the 〈001〉 directions. For superconductivity to occur in this and other doped cuprate compounds, the size of the dopant free regions in the basal plane may have to exceed the superconducting coherence length.