ANOMALOUS X-RAY DIFFUSE-SCATTERING STUDY OF LOCAL ORDER IN ND2-XCEXCUO4-Y

We have successfully applied the anomalous X-ray diffuse scattering te chnique to study the short-range order and the lattice distortions in the electron-type ceramic superconductor Nd2-xCexCuO4-y. The intensity measurements were made at two energies below the absorption edge of C e. The data set were analyzed using a kinematic diffraction equation e xpanded up to the second order in atomic displacements. The fitted SRO parameters for the composition of Nd1.85Ce0.15CuO4-y suggest the form ation of Ce atom-pairs along the <001> direction. The clustering of th e Ce atoms reduces the disturbance to the parent structure.