57Fe Mossbauer spectroscopic investigation of complex magnetic structures in Ga, Sc, and In substituted M-type hexagonal ferrites

Investigation of preliminary evidence that Ga, Sc, and In influence the bulk and dynamic magnetic properties of hexagonal ferrites by means other than those supported in existing models has been undertaken. In SrFe12-xMxO19 (M=Ga, In) and BaFe1-2xScxO19, the predominant 12k sublattice exhibits a remarkable splitting into two distinct subpatterns, 12k(1) and 12k(2) :At x = 0.3, hyperfine fields, H-eff for 12k(1) are 411, 408, and 405 kOe, respectively, and for 12k(2) are 358, 339, and 311 kOe, respectively. The 12k(1) hyperfine field values are virtually unchanged from that of the pure hexagonal ferrites and are independent of substitution level. Contrastingly, the abruptness of the drop in the 12k(2) hyperfine field and its dependence on the nature of the substituting cation are remarkable. The relative intensity of the 12k(2) component correlates with the concentration of nonmagnetic species on the 2b and 4f(2) sites and with the magnetic anisotropy. Scandium seems to have a more profound influence on the magnetic structure and interactions than indium or gallium. Further, at technically significant substitution levels, H-eff of the different sublattices exhibit broad and overlapping distributions of values far removed from their distinctiveness in the pure hexaferrites. Thus, the net magnetization of Ga, Sc, and In-doped hexaferrites results from a complex interplay of magnetic dilution on the 2b site, enhancement of the magnetization through substitutions on the 4f(2) site, and a complex influence from the substitution-induced 12k(2) sublattice. (C) 1999 American Institute of Physics. [S0021-8979(99)53708-0].