Study of features of the composition, magnetic, and crystal structure of barium hexaferrite BaFe$_{12-x}$Ti$_{x}$O$_{19}$

The features of the composition, crystal, and magnetic structure of Ti-substituted barium hexaferrite BaFe$_{12-x}$Ti$_{x}$O$_{19}$ (0.25 $\le x\le$ 1.5) are studied by Mössbauer spectroscopy, vibration magnetometry, X-ray diffraction, and simultaneous thermal analysis. Bounded heterovalent isomorphism implemented by the scheme 2Fe$^{3+}\to$Ti$^{4+}$+Fe$^{2+}$ while retaining the charge balance is established when Fe$^{3+}$ ions are partially substituted with Ti$^{4+}$ ions. An increase in the 3$d$-electron density and the presence of Fe$^{2+}$ in BaFe$_{12-x}$Ti$_{x}$O$_{19}$ samples with $x$ = 1.5 is detected by Mössbauer spectroscopy. The heterovalent isomorphic substitution limit is determined to be within 0.75 $<x<$ 1.0. Using Mössbauer spectroscopy and X-ray diffraction, the formation of titanium-contained phases at $x$ = 1.0 whose content increases with the degree of substitution is shown. The data on the preferential distribution of substituent ions (Ti$^{4+}$) in the barium hexaferrite structure at the 12$k$ and 2$b$ sites are presented.