Magnetic Raman scattering from 1D antiferromagnets

Abstract

We study Raman scattering from 1D antiferromagnets within the Fleury-Loudon scheme by applying a finite temperature Lanczos method to a 1D spin-half Heisenberg model with nearest-neighbor ( J₁) and second-neighbor ( J₂) interactions. The low-temperature spectra are analyzed in terms of the known elementary excitations of the system for J₂ = 0 and J₂ = ½. We find that the low- T Raman spectra are very broad for |J₂/J₁|≤0.3. This broad peak gradually diminishes and shifts with temperature, so that at T > J₁ the spectra are narrower and peaked at low frequencies. The experimental spectra for CuGeO₃ are discussed in light of our calculations.