Ferrite can be divided into five types according to different magnetic properties and application scenarios: soft magnetic, permanent magnetic, gyromagnetic, rectangular - loop magnetic, and piezomagnetic.
Soft Magnetic Materials
These materials are easily magnetized and demagnetized under a relatively weak magnetic field, such as zinc - chromium ferrite and nickel - zinc ferrite. Soft magnetic ferrite is a kind of ferrite material with the widest range of applications, the largest variety, the greatest quantity, and high output value at present. It is mainly used as various inductive elements, such as filter magnetic cores, transformer magnetic cores, radio - frequency magnetic cores, and magnetic heads for tape recording and video recording. It is also a key material for magnetic recording elements.
Permanent Magnetic Ferrite
It is a compound with a hexagonal structure of uniaxial anisotropy. It is mainly barium, strontium, and lead ferrites and their composite solid solutions. There are isotropic and anisotropic magnetic types. Since this kind of ferrite material can still retain a relatively strong and constant remanent magnetic property for a long time after the external magnetization field disappears, it can be used to generate a constant and stable magnetic field in the external space. It has a wide range of applications, for example, it is used as a permanent magnet in various electric meters, generators, telephones, speakers, televisions, and microwave devices.
Hard Magnetic Materials
Ferrite hard magnetic materials are not easy to demagnetize after magnetization. Therefore, they are also called permanent magnetic materials or constant magnetic materials, such as barium ferrite and iron - ferrite. It is mainly used in recorders, pick - ups, speakers in telecommunication devices, and magnetic cores of various instruments.
Gyromagnetic Materials
The gyromagnetic property of magnetic materials means that under the action of two mutually perpendicular steady - state magnetic fields and electromagnetic wave magnetic fields, although the plane - polarized electromagnetic wave propagates in a certain direction inside the material, its polarization plane will continuously rotate around the propagation direction. Although metals and alloy materials also have a certain gyromagnetic property, due to their low resistivity and too - large eddy - current loss, electromagnetic waves cannot penetrate deep into them, so they cannot be utilized. Therefore, the application of the gyromagnetic property of ferrite gyromagnetic materials has become a unique field of ferrite. Most gyromagnetic materials form various microwave devices together with waveguides or transmission lines for microwave transmission. They are mainly used in electronic equipment such as radar, communication, navigation, and telemetry.
Rectangular - Loop Magnetic Materials
This refers to ferrite materials with a rectangular - shaped hysteresis loop. Its characteristic is that when a relatively small external magnetic field acts on it, it can be magnetized and reach saturation. After the external magnetic field is removed, the magnetism still remains the same as that at saturation. For example, magnesium - manganese ferrite and lithium - manganese ferrite are such materials. This kind of ferrite material is mainly used in the memory cores of various electronic computers.
Piezomagnetic Materials
These materials refer to ferrite materials that mechanically elongate or shorten in the direction of the magnetic field during magnetization, such as nickel - zinc ferrite, nickel - copper ferrite, and nickel - chromium ferrite. Piezomagnetic materials are mainly used as transducers for the mutual conversion of electromagnetic energy and mechanical energy and as magnetostrictive elements for ultrasonic applications.
