RAMAN-SCATTERING STUDY OF PHONON AND MAGNETIC EXCITATIONS ALONG THE MAGNETIC CHAIN IN CUGEO3

Detailed temperature dependence of (c, c) Raman scattering spectra has been measured for CuGeO3 in the vicinity of spin-Peierls transition t emperature (T-sp). Below T-sp, six peaks at 30, 105, 227, 370, 416, an d 817 cm(-1) have been observed. We newly observed a peak at 416 cm(-1 ). The energy of the 30 cm(-1) peak decreases continuously with increa sing temperature and becomes zero above T-sp. The peak at 30 cm(-1) is assigned as the soft mode in the spin-Peierls phase from the agreemen t with the temperature dependence of the super-lattice reflection inte nsity. The peak at 227 cm(-1) is assigned as a two-magnon along the c- axis (Cu chain direction). The peaks at 370, 416, and 817 cm(-1) are a ssigned as the phonons, which appear by the symmetry change. The new p eaks of (c, c) are not sensitive to the magnetic field along the alpha -axis below 9 T at 4.7 K.