Hyperfine interactions and thermal motion of iron nuclei in hexagonal barrium ferrite

A Moessbauer study of the hexagonal barium ferrite BaFe12O19 is reported. Polycrystalline and monocrystalline specimens are used, temperature of measurements varied from 4.2 to 750 deg K. The parameters of hyperfine interactions of Fe57 nuclei in the lattice of BaFe12O19 at room temperature are presented. Special attention is paid to studying the hyperfine interactions and thermal motion of Fe57 nuclei in 2b- positions (oxygen surrounding in the shape of a trigonal bipyramid). For the constant of quadrupole interaction of these nuclei at 4.2 deg K the value Δ Esub(Q)=2.3 mm/sec is obtained. Temperature dependence of anisotropy of thermal vibrations of nuclei in 2b- position is studied and the conclusion has been made on the shift of these nuclei from the center of the bipyramid in the temperature of 80 deg K