Ferrite is divided into soft magnetic ferrite and permanent magnet ferrite.
Soft Ferrite Magnets
There are manganese ferrite (MnO·Fe2O3), zinc ferrite (ZnO Fe2O3), Ni-Zn Fe2O4, manganese magnesium zinc ferrite (Mn-Mg-Zn·Fe2O4), etc. Single component or multi-component ferrite. The resistivity of soft magnetic ferrite material is much higher than that of metal magnetic materials, and it has high dielectric properties. Therefore, ferromagnetism and ferromagnetism, ferromagnetism and piezoelectric ferrite are found. The soft magnetic ferrite material has a much higher magnetic conductivity than metallic magnetic material (including ferro-nickel alloy and aluminum ferrosilicon alloy) at high frequency, which is suitable for several thousand Hertz to several hundred megahertz frequencies. Processing ferrite belongs to general ceramic technology, so the process is simple, and save a lot of precious metal, low cost. The saturation flux density of ferrite is low, usually only 1/3 ~ 1/5 of iron. The magnetic energy storage of ferrite in unit volume is low, which limits its application in low frequency, strong power and high power fields requiring high magnetic energy density. It is suitable for high frequency low power and weak current applications. Nickel-zinc ferrite can be used as radio antenna magnet and medium frequency transformer magnetic core, manganese zinc ferrite can be used as the line output transformer core of TV receiver. In addition, the soft magnetic ferrite is also used in the communication line of the inductor and the filter of the magnetic core. In recent years, high frequency magnetic recording transducers (magnetic heads) are also used.
Permanent Ferrite Magnets
There are barium ferrite (BaO·6Fe2O3) and strontium ferrite (SrO·6Fe2O3). The high resistivity is a type of semiconductor, so the eddy current loss is small and the force is large, which can be used effectively in the magnetic circuit of air gap, especially for the permanent magnet of small generator and motor. It does not contain precious metal nickel, cobalt and so on, the raw material source is rich, the craft is not complex, the cost is low, can replace the aluminium nickel cobalt permanent magnet. Its maximum magnetic energy product (B+H)m is lower, so it is larger than a metal magnet in the case of equal magnetic energy. Its temperature stability is poor, the texture is brittle, fragile, not resistant to shock vibration, not suitable for measuring instruments and precise requirements of magnetic devices. The products of permanent magnet ferrite are mainly anisotropic series. They can be used to make permanent magnet ignition motor, permanent magnet motor, permanent magnet separator, permanent magnet crane, magnetic thrust bearing, magnetic separator, speaker, microwave device, magnetic disc, hearing aid, etc.