North-Holland Letter to the Editor

s’Fe Mossbauer spectra of PbFe,,O,, have been obtained at 295 K on polycrystalline and single-crystal thin sections oriented with the c-axis parallel and perpendicular, respectively, to the y-ray propagation direction. Due to the lower Ntel temperature, the internal magnetic fields (I&t) in PbFe,,O,s are lower than those in BaFet,Ot, and SrFetzOI, but the systematics of the hyperfine interactions are similar to those in other hexaferrites. For example, the relative values of H,,, exhibit the following sequence: 2b < 12k < 4f, < 2a < 4f, and the isomer shifts (6) exhibit the following ordering: 4f, < 2b < 2a 5 12k-C 4f,. The large dynamic displacement of the 2b Fe 3+ ion parallel to the c-axis is clearly demonstrated by the relative intensity of the 2b site for the two oriented single crystals, being negligible for the crystal perpendicular to the c-axis, and equal to its population fraction for the crystal parallel to the c-axis. The lower value for the electric quadrupole splitting of the 2b site is believed to be related to the larger dynamic displacements at this site compared to other hexaferrites. 1