A study of the two-magnon Raman scattering in the Heisenberg antiferromagnets CoF2and FeF2using a realistic model hamiltonian

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Abstract
The electrical susceptibility for the two-magnon Raman scattering in Heisenberg antiferromagnets with single-ion anisotropy and exchange integrals up to the third neighbours is derived by means of an equation of motion method and decoupling procedure. The calculated Raman lineshapes for CoF2 and FeF2 in different geometries at T=0 are compared with the experimental findings when available. In the case of CoF 2 the two distinct peaks at the 112 cm-1 and 115 cm-1 respectively observed in the xy and xz geometries by Dugautier et al. are reproduced. For FeF2 a good agreement is found with the experimentally observed width (6.0 cm-1) and peak position (153.5 cm-1) provided due account is taken of the instrumental resolution function. The possibility of deriving the exchange parameters in the hamiltonian by means of light-scattering experiments is briefly discussed.