Composite oxides composed of iron oxides and one or several other metal oxides (such as BaO · 6Fe2O3, MnO · Fe2O3 · ZnO · Fe2O3, etc.) are called ferrite. Ferrite with Ferrimagnetism is a kind of strong magnetic material, which is generally called ferrite magnetic material. FeO · Fe2O3 (Fe3O4) is the simplest and earliest applied natural ferrite magnetic material in the world. Ferrite magnetic materials can be divided into soft magnetic, hard magnetic (including bonding), rotational magnetic, moment magnetic, and piezoelectric magnetic, as well as other ferrite materials. Their composition, crystal structure, characteristics, and application fields are shown in the table below. Their main characteristics are: high permeability, low Coercivity and low loss of soft magnetic materials; The Coercivity of hard magnetic materials is high, and the magnetic energy product (BH) is high; The gyromagnetic material has the gyromagnetic property, that is, when the electromagnetic wave propagates along the direction of a constant magnetic field, its vibration surface continuously rotates along the propagation direction. The gyromagnetic material is mainly used for Microwave transmission devices. Moment magnetic materials have rectangular B-H hysteresis loops, mainly used for computer storage magnetic cores; Piezomagnetic materials have a large linear magnetostrictive coefficient λ S. Ferrite magnetic materials have been widely used in computer, Microwave transmission, television, automatic control, aerospace, instrumentation, medical treatment, automobile industry and other fields, among which hard magnetic and soft magnetic ferrite materials are the most widely used