Cationic and anionic modifications of La2-xSrxCu1-yRuyO4-delta studied by Raman spectroscopy

Crystalline La2-xSrxCu1-yRuyO4-delta samples were prepared by solid state r eactions in the compositional range 0.1 less than or equal to y less than o r equal to 1 and approximately 1.8y + 0.2 < x < 1.5y + 1. The samples are e ither undoped (delta = 0) or have oxygen deficiencies (delta > 0). The Rama n spectra of all samples are dominated by the vibrational modes of the RuO6 octahedrons. The corresponding features of the modes related to the CuO6 o ctahedrons are much weaker in the spectra. For delta = 0, the material is h omogeneous whereas, for delta > 0, the Raman studies reveal a segregation e ffect. The formation of microscopic clusters of Sr2RuO4 (with Ru4+) takes p lace within a La2-x'Srx'Cu1-y'Ruy'O4-delta' host, where the RuO6 octahedron s contain predominantly Ru5+. (C) 2001 Elsevier Science Ltd, All rights res erved.