Magnetic properties of hexagonal oxide ferrimagnets with orientational transitions

We study the magnetic structure of different types of hexaferrites, BaCoxTixFe12−2xO19(M), BaCo2−xZnxFe16O27(W), and Ba3Co2.4Ti0.4Fe23.2O41 (Z), and determine the concentration and temperature regions whre magnetically ordered phases such as the cone, plane, and axis of easy magnetization phases exist and the order of the magnetoorientational phase transitions. The constants of magnetic crystal anisotropy, including those of a higher order, were determined using polycrystalline textured samples. We estimate the exchange integrals for the main structural types of hexaferrites, M, W, Y, and Z. Based on these values, we show that it is possible to make a quite reliable prediction about the concentration and temperature dependence of such basic characteristics of hexaferrites as magnetization and anisotropy fields.