Superlattice modulation and superconductivity in the electron-doped Nd2CuO4-xFx and Nd2-xCexCuO4 systems

C. H. Chen, D. J. Werder, A. C.W.P. James, D. W. Murphy, S. Zahurak, R. M. Fleming, B. Batlogg, L. F. Schneemeyer

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Abstract

We have observed a periodic superlattice modulation in Nd2CuO4 and in the "electron-doped" Nd2CuO4-xFx and Nd2-xCex-CuO4 by electron diffraction and microscopy. The superlattice modulation characterized by a wave vector q=( 1 4 1 4,0) parallel to the Cu-O plane was found in both superconducting and non-superconducting samples, but most of the samples examined were not homogeneous with respect to the superlattice. The orthorhombic superlattice phase is found to exist in four possible variants with its c-axis parallel to the four equivalent [111] zone-axes in the underlying tetragonal lattice. Samples quenched from high temperature invariably showed no superlattice or superconductivity; bulk superconductivity and regions of superlattice were observed on annealing in the range 250-750°C. We believe that oxygen migration is responsible for this disproportionation into superlattice and nonsuperlattice regions.

Original languageEnglish
Pages (from-to)375-380
Number of pages6
JournalPhysica C: Superconductivity and its applications
Volume160
Issue number3-4
DOIs
StatePublished - 15 Sep 1989

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