Magnetoplumbite-Related Oxides

These ferrites were prepared from Fe{sub 2}O{sub 3}, MO oxides (M = Ba,Sr,Pb) and MeO oxides (Me = Mg,Mn,Co,Zn). Chemical compositions of the main barium ferrites (M = Ba) are represented in a ternary diagram. The structures of these various compounds (M,Y,W,Z,X,U) are closely related. The simplest one is the compound BaFe{sub 12}O{sub 19} (M). Its crystal structure is similar to that of the mineral magnetoplumbite PbFe{sub 7.5}Mn{sub 3.5}Al{sub 0.5}O{sub 19} (PbM{sub 12}O{sub 19}) (5). For this reason the hexagonal ferrites are also known as magnetoplumbite-type ferrites (called MP-type in this paper). When the Fe{sup 3+} ions are replaced by other trivalent ions, such as Al{sup 3+}, Ga{sup 3+}, another group of MP-type oxides, namely AB{sub 12}O{sub 19} (A = Ba{sup 2+} or a large divalent ion; B = Al{sup 3+} or Ga{sup 3+}) is obtained. In this paper, the authors briefly review ideal structure and major properties and uses, especially in the case of ferrites.