A high temperature electrochemical oxidation process has been used to produce large single crystals of La2CuO4+δ suitable for neutron scattering experiments. Below room temperature the oxygen-rich phases have structural superlattice scattering peaks which indicate new periodicities ranging from 2 to 6.6 layers perpendicular to the copper oxide planes. A model structure originally proposed for La2NiO4+δ can account for the superlattice peaks as a result of antiphase domain boundaries between different tilt directions of the CuO6 octahedra. Within this model, the changes in CuO6 tilt directions are induced by segregated layers of interstitial oxygen which order in a manner similar to intercalants in graphite. This structural model thus clarifies previous work and establishes La2CuO4+δ as a unique lamellar superconducting system with annealed disorder. PACS Index Nos: 74.72.Dn, 74.25.Dw, 74.80.Dm, 61.12.-q 1
To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.