Structural investigation of high-Tc superconductor EuBa2Cu3Oy by microRaman spectroscopy

Polycrystalline EuBa2Cu3Oy (EuBCO) samples with various oxygen contents (y 6.25, 6.38 and 6.8) have been analysed by means of microRaman spectroscopy. The usual Raman features of REBa2Cu3Oy high temperature superconductors (RE Y, Eu, Sm, Er¼) have been con®rmed also for EuBCO. A correlation between the crystal structure and the conductivity properties as a function of the oxygen content has been established by studying in detail the features of the different Raman spectra. In particular, the analysis of the peak pro®les of lattice vibrations involving oxygen atoms provides important information to understand the anomalous superconducting properties found in the sample with y 6.38. In addition, the appearance in the superconducting samples of a new mode centred at 223 cm21 may be correlated to ordering phenomena which have been called to justify the conductivity results.