On synthesis of BaFe$_{12}$O$_{19}$, SrFe$_{12}$O$_{19}$, and PbFe$_{12}$O$_{19}$ hexagonal ferrite ceramics with multiferroid properties

We analyze the possibility of obtaining M-type hexagonal ferrites of barium, strontium, and lead with multiferroid properties with the help of ceramic technology. Using the modified ceramic technology (especially pure initial raw materials, admixture of B$_2$O$_3$, and sintering in the oxygen atmosphere), we obtained for the first time the BaFe$_{12}$O$_{19}$ and SrFe$_{12}$O$_{19}$ samples with intense multiferroid properties at room temperature. At the same time, the employed technology does not make it possible to obtain PbFe$_{12}$O$_{19}$ samples exhibiting ferroelectricity. The multiferroid characteristics of experimental samples are compared with the characteristics of classical high-temperature multiferroic BiFeO$_3$ and with the characteristics of BaFe$_{12}$O$_{19}$, SrFe$_{12}$O$_{19}$, and PbFe$_{12}$O$_{19}$ ferrite ceramics obtained in accordance with polymer precursor technology. We propose a mechanism explaining multiferroid properties of the hexagonal ferrite ceramic samples and note the importance of our results for applications.