Theoretical Analysis of Peculiarities of Phase Formation of Ferromagnetics of CoO – BaO – Fe₂O₃ System

The physical and chemical peculiarities of ferromagnetic phase formation in the CoO - BaO - Fe<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> system are analysed. The choice of the studied system from the point of view of obtaining traditional ceramic ferrites on the basis of binary compounds of the system is justified, and the possibility of obtaining ferromagnetics on the basis of ternary oxides of the above system is shown. The results of calculation of the Gibbs free energy change with temperature for model reactions simulating all possible variants of synthesis and decomposition of ternary oxide compounds of the above system are presented. Localisation of compositions of all ternary compounds in the CoO - BaO - Fe<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> system is theoretically determined, which may be important for explaining the reason of the increase of magnetic properties of barium hexaferrite-based ferrites. It is indicated that the peculiarities of phase formation of ternary oxides in the high-iron region of the CoO - BaO - Fe<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> system should be taken into account in the manifestation of the induced magnetic anomaly effect and the corresponding purposeful control of the properties of ferrites of complex composition.