Applications Of Different Kinds Of Permanent Magnets

NdFeB magnets have outstanding magnetic performance advantages compared to other permanent magnet materials.

It has a very high magnetic energy product, coercive force, and energy density, and is called "Magnet King" with good mechanical properties and easiness to process. These excellent properties make NdFeB neodymium permanent magnets widely used in modern industry and electronic technology, such as permanent magnet motors, loudspeakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment and so on. In 2000, the output value of rare earth permanent magnets exceeded that of ferrite/ceramic magnet for the first time. In 2010, the output value of NdFeB neodymium magnets exceeded that of ferrite/ceramic magnet and became the real "main character" in the permanent magnet industry.

By manufacturing techniques, NdFeB neodymium magnets can be divided into three types: sintered, bonded and hot-pressed. Each of the three magnets has its own characteristics in terms of performance, which make them unique in applications:

Sintered NdFeB neodymium magnet has the highest output and is the most widely used rare earth permanent magnet. Sintered NdFeB neodymium magnet has high magnetic energy product, high coercive forces, and high working temperature, but its tolerance is relatively hard to control and not good for small size, therefore it is mainly used in large and medium-sized motors, wind turbines, high fidelity loudspeakers and etc.

Bonded NdFeB neodymium magnet has an irreplaceable position in many fields of applications. The magnetic properties of bonded NdFeB are not as good as that of sintered NdFeB, but it has the advantages of simple production, low cost, small size, high precision, and stable magnetic field. There are few alternatives to bonded NdFeB in certain applications for information technology, office automation, consumer electronics, and other fields.

Hot pressed NdFeB is excellent in performance but limited in applications. Compared with sintered NdFeB, hot pressed NdFeB has advantages in precision control, yield rate, temperature resistance, corrosion resistance, and cost. The production output of hot pressed NdFeB is still small, far behind the bonded and sintered NdFeB neodymium magnets.

Bonded NdFeB, sintered NdFeB and hot pressed NdFeB neodymium magnets to have their own characteristics in performance and applications. The overlapping areas of downstream applications are limited, thus they complement each other more than a substitute for each other. Firstly, bonded NdFeB and sintered NdFeB neodymium magnets have great differences in performance. Bonded NdFeB is mainly used in various micro motors, while sintered NdFeB is widely used in large and medium-sized motors. The future of bonded NdFeB will be most likely a substitute for ferrite/ceramic magnet in the middle and low-end areas, rather than directly threatening the markets for sintered NdFeB. Secondly, the market for hot-pressed NdFeB is still small, and it will not have a significant impact on the application of sintered NdFeB neodymium magnet for a long time in the future. The cost and performance of hot-pressed NdFeB are better than that of sintered NdFeB, having the potential to replace sintered NdFeB in many fields such as automotive EPS, wind turbines, air-conditioning compressors and so on. However, due to the limitations of production techniques at this stage, hot-pressed NdFeB can only be made into rings, which greatly limits its application range. At present, hot pressed NdFeB is mainly used in the field of automotive EPS motor.

Permanent ferrite/ceramic magnets

Although permanent ferrite/ceramic magnets have lower magnetic performance, compared with metal permanent magnets, ferrite/ceramic magnets have higher resistivity, better stability, stronger resistance towards environmental changes, rich raw material source, higher cost efficiency and simple production process without oxidation problem. Therefore, it is widely used in mid and low-end products with low magnetic performance requirements. Permanent ferrite/ceramic magnet has wide applications: it is an important part of automobile motors, consumer electronics, household appliances, computers, communication products, and other consumer goods.

Samarium cobalt magnets

Samarium cobalt magnets have excellent magnetic stability, the extremely low-temperature coefficient (-0.030%/°C), heat resistance (up to 500 °C) and superior rust resistance. These characteristics are not available in NeFeB neodymium magnets. In addition, SmCo magnets have relatively high magnetic performance (high magnetic energy product, high coercive force, high remanence),  therefore SmCo permanent magnets are very suitable for use in poor working environments. SmCo magnets have been widely used in aerospace, defense, military, microwave devices, communications, medical equipment, instruments, wind power generation, various magnetic transmission devices, sensors, magnetic processors, high-end motors and other industries.

AlNiCo magnets

Aluminum nickel cobalt magnet is the permanent magnet material with the highest Curie temperature. Its working temperature can be up to 600 °C. It has a low-temperature coefficient, high-temperature resistance, moisture resistance, oxidation resistance, and good working stability. AlNiCo magnets are mainly used in places where high magnetic fields and high temperatures are required, such as electric motors, electric guitar pickups, speakers, sensors and traveling wave tubes. In addition, in communication, computer peripherals, micro motors, sensors, and magnetic seals and other applications, AlNiCo magnets are used to make miniaturized and microminiaturized permanent magnet components with complex shapes, and its cost is almost the lowest. Due to its excellent mechanical properties, AlNiCo magnet can be used as a structural part of a complex magnetic circuit.

Rubber magnets

Rubber magnet has the lowest magnetic performance, but because of its flexibility and elasticity, it is very close to people's daily life. Rubber magnets are mainly used in micro motors, refrigerators, disinfection cabinets, kitchen cabinets, toys, educational instruments, advertising materials, switches, and sensors.