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}=14K) 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}=14K 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.
@article{arxiv.cond-mat/9611053,
title = {Substitution effects on spin fluctuations in the spin-Peierls compound CuGeO_3},
author = {M. Fischer and P. Lemmens and G. Güntherodt and M. Weiden and W. Richter and C. Geibel and F. Steglich},
journal= {arXiv preprint arXiv:cond-mat/9611053},
year = {2016}
}