Dispersion relation and inelastic light scattering of antiferromagnetic polaritons

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Abstract
In the long-wavelength region, magnons and photons mix to form modes which may be called magnetic polaritons. Using the Bloch equations of motion and classical electromagnetic theory the authors have calculated the linear response of antiferromagnets to a transverse external RF field. The poles of the response function give the dispersion relations of the polaritons. With a strong exchange field they derive an approximate explicit form of the dispersion relation. With the aid of the fluctuation dissipation theorem the correlation functions which govern inelastic light scattering are derived from the response functions. Expressions are given for the scattering cross section and the frequency-dependent linewidth. The results are illustrated with calculations for MnF2.