Application of ferrite magnet material

Ferrite magnet material is a ferromagnetic metal oxide. In terms of electrical properties, the resistivity of ferrite is much greater than that of metal and alloy magnetic materials, and it also has higher dielectric functions. The magnetic function of ferrite also shows high magnetic permeability at high frequencies. Therefore, ferrite magnet material has become a common non-metallic magnetic material for high frequency and weak current limit. Due to the low magnetic energy retained per unit volume of ferrite and the low saturation magnetization, ferrites are limited in applications requiring high magnetic energy density at low frequency and high power constraints.

Ferrite magnets are manufactured by powder metallurgy. They are mainly divided into two types: barium (Ba) and strontium (Sr), and are divided into two types: anisotropic and isotropic. It is a permanent magnet that is not easy to demagnetize and not easy to corrode. The material, with a maximum working temperature of 250 degrees Celsius, is relatively hard and brittle. It can be cut and processed with tools such as diamond sand, and it can be formed at one time with an alloy processed mold. Such products are widely used in permanent magnet motors (Motor) and speakers (Speaker) and other fields. Mainly applicable to communication, broadcasting, calculation, automatic control, radar navigation, space navigation, satellite communication, instrument measurement, printing, pollution treatment, biomedicine, high-speed transportation, etc.

Ferrite belongs to the category of semiconductors in electronics, so it is also called magnetic semiconductors. Magnetite is a simple ferrite.

1. Permanent ferrites include barium ferrite (BaO.6Fe2O3) and strontium ferrite (SrO.6Fe2O3). High resistivity, belongs to semiconductor category, so eddy current consumption is small, coercive force is large, can be effectively used in air gap magnetic circuit, which is unique for small generators and permanent magnets. It does not contain precious metals such as nickel and cobalt. The raw material is excellent, the process is not complicated, and the cost is low. Can replace AlNiCo permanent magnet. Its high-contrast magnetic energy product is low, so it is larger than metal magnets under considerable magnetic energy conditions. Its temperature stability is poor, its texture is brittle and brittle, and it cannot withstand impact and feel. Not suitable for measuring instruments and magnetic equipment with strict requirements. The products of permanent magnet ferrite are mainly anisotropic series. They can be used to manufacture permanent magnet starter motors, permanent magnet motors, permanent magnet concentrators, permanent magnet suspensions, magnetic thrust bearings, broadband magnetic separators, speakers, microwave equipment, magnetic therapy sheets, hearing aids, etc.

2. Soft magnetic ferrites include manganese ferrite (MnO.Fe2O3), zinc ferrite (ZnO.Fe2O3), nickel zinc ferrite (Ni-Zn.Fe2O4), manganese magnesium zinc ferrite (Mn- Mg-Zn.Fe2O4) and other single or multi-component ferrites. The resistivity is much larger than that of metallic magnetic materials, and it has a higher dielectric function. Thus, ferrites that have both ferromagnetic and ferroelectric properties as well as ferromagnetic and piezoelectric properties emerged. At high frequencies, its magnetic permeability is much higher than that of metallic magnetic materials, including nickel-iron alloys and sendust. It can be applied in the frequency range from a few kilohertz to hundreds of megahertz. The processing of ferrite belongs to the ordinary ceramic process, so the process is simple, and a lot of precious metals are saved, and the cost is low.

The saturation magnetic flux density of ferrite is very low, usually only 1/3-1/5 of that of iron. Ferrite has a low magnetic energy reserve per unit volume, which limits its use at low frequencies, high currents, and high power band borders where high magnetic energy density is required. It is more suitable for high frequency, low power and weak electric field surface. Nickel zinc ferrite can be used as antenna pole and intermediate frequency transformer core in radio broadcasting, and manganese zinc ferrite can be used as line transmission transformer core in TV receiver. In addition, soft ferrites are used to add sensors and filter cores in communication lines. High frequency magnetic recording transducers have been used for many years.