Common Magnetic Materials in Permanent Magnets

The magnetic materials used in permanent magnets are AlNiCo, ferrite permanent magnet materials and rare earth permanent magnet materials. 

Al-Ni-Co alloy is developed from Al-Ni-Fe alloy. AlNiCo magnets have low coercivity, so any iron should be strictly prohibited from contacting AlNiCo permanent magnet materials during use to avoid local demagnetization of permanent magnets and distortion of the magnetic flux distribution in the magnetic circuit. The advantage of AlNiCo magnets is that the temperature coefficient is small, and the degradation of permanent magnet characteristics due to temperature changes is also small. However, the material is hard and brittle, so its processing is difficult. The main applications of AlNiCo are in electronic ignition systems, watt-hour meters, voltammeters, medical instruments, industrial motors and other fields.

Ferrite permanent magnet material is one of the most widely used permanent magnet materials, and its main component is MoFe₂O₃. It has the advantages of large coercive force, light weight, abundant source of raw materials, low price, oxidation resistance, corrosion resistance, large anisotropy constant of the magnetic crystal, and its demagnetization curve is approximately a straight line. And its disadvantages are that the remanence is low, the temperature coefficient is large, and it is fragile. The coercivity of ferrite permanent magnet materials is between that of AlNiCo alloy materials and rare earth cobalt permanent magnet materials. Since its low remanence, it is generally suitable to be designed into a flat shape. Ferrite magnetic materials are mainly used in fields such as motors, speakers, toys, and handicrafts.

Rare earth permanent magnetic materials have the advantages of high coercivity, large maximum magnetic energy product, and reversible permeability. Therefore, their magnetic properties far exceed other magnetic materials such as ferrite and AlNiCo. The emergence of rare earth permanent magnet materials has led to the emergence of permanent magnet synchronous motors with light weight and small size, thus expanding the application range of permanent magnet synchronous motors. The rare earth cobalt permanent magnet material has excellent performance. However, its price is relatively high, so it is necessary to make careful calculations when designing, and strive to achieve the desired effect with the smallest volume. Due to the high coercivity of rare earth cobalt permanent magnet materials, it can be made into sheet permanent magnet materials to reduce volume and save materials.

The performance of injection molded ferrite and injection molded rare earth materials is lower than that of sintered materials. However, due to its unique advantages, it has gradually replaced sintered permanent magnet materials as new permanent magnet materials in small and micro motors, sensors and other fields.