Magnons and sublattice magnetisations in hexagonal Ba ferrite

Magnon spectra in the hexagonal ferrite BaFe12O19 are calculated using the exchange integrals obtained from the analysis of the temperature dependence of NMR corresponding to 57Fe nuclei in magnetic domains. From the magnon spectra the zero-point spin deviations and the temperature dependence of sublattice magnetisations are determined. For comparison all calculations are also performed with an alternative set of the exchange integrals taken from the literature.