Cationic and anionic modifications of La2−xSrxCu1−yRuyO4−δ studied by Raman spectroscopy

Crystalline La2−xSrxCu1−yRuyO4−δ samples were prepared by solid state reactions in the compositional range 0.1≤y≤1 and approximately 1.8y+0.2<x<1.5y+1. The samples are either undoped (δ=0) or have oxygen deficiencies (δ>0). The Raman spectra of all samples are dominated by the vibrational modes of the RuO6 octahedrons. The corresponding features of the modes related to the CuO6 octahedrons are much weaker in the spectra. For δ=0, the material is homogeneous whereas, for δ>0, the Raman studies reveal a segregation effect. The formation of microscopic clusters of Sr2RuO4 (with Ru4+) takes place within a La2−x′Srx′Cu1−y′Ruy′O4−δ′ host, where the RuO6 octahedrons contain predominantly Ru5+.