Isotope effects in CuGeO3 studied by Raman spectroscopy

Effects of isotopic substitution of Cu and Ge in CuGeO3 are studied by Raman spectroscopy. We present detailed information on the isotope-induced shifts of nearly all Raman modes in the dimerized phase of CuGeO3. Our study unambiguously reveals phononic contributions to the asymmetric Raman peaks observed at 108 and 228 cm−1 which have been related to magnetic excitations previously. Furthermore, we observed an upshift by 0.9±0.1 cm−1 for the two-magnon bound state at 30 cm−1 in 65CuGeO3 compared to natCuGeO3.