RAMAN-SCATTERING STUDY OF CUGEO3 IN THE SPIN-PEIERLS PHASE

Phonons and magnetic excitations were studied as a function of temperature in the spin-Peierls phase of an inorganic material CuGeO3 by Raman scattering. All of the phonon Raman peaks observed at room temperature can be assigned on condition that the crystal symmetry is D2h5(Pbmm). Five peaks intrinsic to the spin-Peierls state were observed at 30, 105, 228, 370, and 818 cm-1 in the spin-Peierls phase. The temperature dependence of the frequency of the 30-cm-1 peak agrees approximately with 2Δ(T), where Δ(T) is the spin-Peierls gap. The Raman spectrum between 0 and 300 cm-1 was compared with the density of states of the magnetic excitons. The 105- and 228-cm-1 peaks were assigned to two-magnetic-exciton Raman scattering. The peaks at 370 and 818 cm-1 were assigned to one-phonon Raman scattering of the folded Ag modes, which occurs due to the formation of a dimerization in the spin-Peierls phase. © 1994 The American Physical Society.