Two-Magnon Raman Scattering in CuGeO₃ Which Undergoes Spin-Peierls Transition

Abstract

Magnetic properties of CuGeO₃ were investigated by Raman scattering. Broad two-magnon scattering extending over 2000 cm⁻¹ develops below 200 K. This wide energy indicates that the spins are two-dimensional, that is, the interchain ferromagnetic exchange energy is ten times larger than the intrachain antiferromagnetic exchange energy. The two-dimensionality is against the current interpretation of the spin-Peierls transition. The intensity below 1000 cm⁻¹, especially below 100 cm⁻¹, decreases below 50 K due to the dimeric lattice distortion.