LIGHT-SCATTERING FROM MAGNETIC-ENERGY FLUCTUATIONS IN THE ONE-DIMENSIONAL HEISENBERG-ANTIFERROMAGNET KCUF3

Inelastic light scattering by magnetic-energy fluctuations has been ob served in the one-dimensional Heisenberg antiferromagnet KCuF3 using a conventional Raman spectrometer. The scattering, having a peak in the cross section at zero frequency and completely distinguished from Ray leigh scattering, is observed over an extremely wide range of temperat ure above T-N = 39 K. The scattered light is strongly polarized and it s line profile around zero frequency is well fitted on a Lorentzian cu rve. The cross section increases with increasing temperature above T-N Our experimental data are well explained by the theory which Halley d eveloped introducing the hydrodynamic form for the correlation functio n of magnetic-energy density given by Halperin and Hohenberg. The abse nce of such inelastic scattering in K2CoF4 (a two-dimensional Ising an tiferromagnet) and K2CuF4 (a two-dimensional Heisenberg ferromagnet) i n a Raman spectrum is also discussed.