Ferrite is made of iron oxide and other ingredients. Generally, it can be divided into permanent ferrite, soft ferrite and rotary ferrite.

Permanent ferrite, also known as ferrite magnetic steel, is a small black magnet we usually see. The main raw materials are iron oxide, barium carbonate or strontium carbonate. After magnetization, the intensity of the residual magnetic field is very high and can be maintained for a long time. It is usually used as permanent magnet material. For example: loudspeaker magnet.

Soft ferrite is prepared by sintering Fe2O3 and one or several other metal oxides (such as nickel oxide, zinc oxide, manganese oxide, magnesium oxide, barium oxide, strontium oxide, etc.). The reason why it is called soft magnetism is that when the magnetizing magnetic field disappears, the residual magnetic field is very small or almost No. It is usually used as a choke or as the core of an intermediate frequency transformer. This is completely different from permanent ferrite.

Gyromagnetic ferrite is a kind of ferrite material with gyromagnetic properties. The gyromagnetism of magnetic materials refers to the phenomenon that under the action of two mutually perpendicular DC magnetic fields and electromagnetic wave magnetic fields, the plane of polarization of electromagnetic waves will rotate around the propagation direction continuously in the process of propagating in a certain direction. Gyromagnetic ferrite has been widely used in microwave communication. According to the crystal types, gyromagnetites can be divided into spinel type, garnet type and magnetoplumbite type (hexagonal type).