Substitution effects on spin fluctuations in the spin-Peierls compound CuGeO3

Abstract Using Raman scattering we studied the effect of substitutions on 1D spin fluctuations in CuGeO 3 observed as a spinon continuum in frustration-induced exchange scattering. For temperatures below the spin-Peierls transition ( T SP = 14 K) the intensity of this continuum at 120–500 cm −1 is exponentially suppressed and transferred into a 3D two-magnon density of states. Besides a spin-Peierls gap-induced mode at 30 cm −1 and additional modes at 105 and 370 cm −1 are observed. Substitution of Zn on the Cu site and Si on the Ge site of CuGeO 3 quenches easily the spin-Peierls state. Consequently, a suppression of the spin-Peierls gap observable below T SP = 14 K as well as a change of the temperature dependence of the spinon continuum are observed. These effects are discussed in the context of a dimensional crossover of this compound below T SP and strong spin-lattice interaction.