FE-57 MOSSBAUER INVESTIGATION OF ORIENTED SINGLE-CRYSTAL AND POLYCRYSTALLINE PBFE12O19

[摘要] Fe-57 Mossbauer spectra of PbFe12O19 have been obtained at 295 K on polycrystalline and single-crystal thin sections oriented with the c-axis parallel and perpendicular, respectively, to the gamma-ray propagation direction. Due to the lower Neel temperature, the internal magnetic fields (H(eff)) in PbFe12O19 are lower than those in BaFe12O19 and SrFe12O19 but the systematics of the hyperfine interactions are similar to those in other hexaferrites. For example, the relative values of H(eff) exhibit the following sequence: 2b < 12k < 4f1 < 2a < 4f2 and the isomer shifts (delta) exhibit the following ordering: 4f1 < 2b less-than-or-equal-to 2a less-than-or-equal-to 12k < 4f2. The large dynamic displacement of the 2b Fe3+ 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.

[发布日期] 1991-04-01