VIBRATIONAL PROPERTIES OF COPPER METAGERMANATE (CUGEO3) SINGLE-CRYSTALS

We present the polarized far-infrared and Raman spectra of CuGeO3 sing le crystals in the temperature range between 10 and 300 K. Assignation s of vibrational modes were performed on the basis of factor-group and normal-coordinate analyses. The frequencies of the infrared-active mo des are determined using an oscillator-fitting procedure of reflectivi ty data. In the Raman-scattering spectra, besides phonon modes, two br oad structures at about 500 and 1600 cm-1 are observed. The temperatur e dependences of the frequency, full width at half maximum (FWHM) and integrated intensities of these modes suggest their magnetic origin. I n the temperature range we considered, no evidence of the spin-Peierls -transition contribution to the phonon and magnon spectra is found.