Mössbauer Studies and the Microwave Properties of Al³⁺- and In³⁺-Substituted Barium Hexaferrites

The correlation of the chemical composition, the structure, and the microwave characteristic of solid solutions of the BaFe_12–xD_xO₁₉ (0.1 ≤ x ≤ 1.2) barium hexaferrite substituted with diamagnetic Al³⁺ and In³⁺ ions has been studied. The precise data on the crystal structure have been obtained by powder neutron diffraction using a high-resolution Fourier diffractometer (Dubna, JINR). The data on the distribution of the diamagnetic substituting ions in the hexaferrite structure have been obtained by Mössbauer spectroscopy. The microwave properties (the transmittance and the reflectance) have been studied in the frequency range 20–65 GHz and in external magnetic fields to 8 kOe. It is found that the transmission spectra are characterized by a peak that corresponds to the resonant frequency of the electromagnetic energy absorption, which is due to the ferromagnetic resonance phenomenon. The correlation of the chemical composition, the features of the ion distribution in the structure, and the electromagnetic properties has been revealed. It is shown that external magnetic fields shift the absorption peak of electromagnetic radiation to higher frequencies due to an increase in the magnetocrystal anisotropy. The results enable the conclusion that the features of the intrasublattice interactions and the electromagnetic properties should be explained using the phenomenological Goodenough–Kanamori model.