Topotactical reactions with ferrimagnetic oxides having hexagonal crystal structures—I

A new method is described for the preparation of polycrystalline materials with oriented crystals by reaction of the oriented grains of a strongly anisotropic ferrimagnetic with non-oriented grains of usually non-magnetic components. Using this type of reaction, for which the name “topotactical (or “topotaxial”) reaction” is proposed, oriented samples of Ba3CoδZn2−δFe24O41, BaCoδZn2−δFe16O27, Ba2Zn2Fe12O22 and BaCoδTiδFe12−2δO19, which have related hexagonal crystal structures, have been prepared as well as some ferrites having the cubic spinel structures.