Vibrational properties of copper metagermanate (CuGeO3) single crystals

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