What are magnets?

Magnets narrowly defined as permanent magnets, rare earth magnetic materials or hard magnetic material, which have consistent and lasting magnetic strength or magnetic field to attract ferromagnetic substance. It commonly known as “magnets”.

General speaking, a magnet is not only just a permanent magnet, but also a substance or material that can generate a magnetic field under certain condition which scientific name is magnetic material.

1.According to the form of magnetic field and the application of special magnetic fields, magnetic materials can be divided into three categories:Permanent magnet materials, Soft magnetic material, Other functional magnetic materials.

 1.1 Permanent magnet materials

Permanent magnet materials also known as hard magnetic materials are with wide hysteresis loop, high coercivity, and high remanence and can maintain constant magnetic properties once magnetized. That is, it is difficult to be magnetized, and difficult to demagnetize once magnetized. General speaking, it is the materials that can still maintain the magnetic force after the magnetic field is removed and features high coercivity and high remanence. In practical applications, the permanent magnet materials work in the second quadrant demagnetization part of the hysteresis loop after deep magnetic saturation and magnetization.

1.1.1 Classification of permanent magnet materials

1.1.1.1 According to the compositions, permanent magnet materials include AlNiCo permanent magnet alloys, FeCrCo permanent magnet alloys, permanent ferrite magnets, rare earth permanent magnet materials and composite permanent magnet materials.

1.1.1.2 According to the production processes, it is divided into cast permanent magnet materials that is cast AlNiCo in actual application, sintered permanent magnet materials, bonded permanent magnet materials, calendaring permanent magnet materials and injected permanent magnet materials.

Sintered permanent magnet materials are brittle mainly include NDFEB magnets, SMCO magnets, ALNICO magnets, ferrite magnets, which finished products need to go through the process of slicing, cutting and grinding. Compared with other magnets with same process, it is much cost-effective.

Bonded permanent magnet materials molded at one time, which mainly include NDFEB magnets, FRRRITE magnets, SMCO magnets and magnetic properties are not as high as those of sintered materials are. A tooling is almost necessary before a mass production.

Calendaring permanent magnet materials mainly include rubber magnets.

Injected permanent magnet materials mainly include NDFEB magnets and rubber magnets.

1.1.1.3 According to the temperature resistance, it divided into normal temperature magnets, high temperature magnets and low temperature coefficient magnets.

Normal temperature magnets generally refer to N-grade such as N30, N35, and N48 NdfeB magnets, which can only work at room temperature. SMCO magnets is the high temperature magnets which can resist 250 degrees Celsius above, that is, the maximum temperature can range from 250 to 500 degrees Celsius. ALNCO magnets have a maximum functional temperature of 550 degrees Celsius. Within the range of magnet working temperature, the magnet with the best temperature resistance coefficient, that is, the smallest temperature coefficient is ALNICO magnets, followed by SMCO magnet and NDFEB magnets with high coercivity that contain special CO components.

1.1.1.4 Magnets can be divided into isotropic magnets and anisotropic magnets according to fact that whether magnets get through the magnetic field orientation during the production process.

Isotropic magnets can be magnetized in any direction while the magnetic force is small, Anisotropic magnets can only be magnetized in the direction of magnetic field orientation while the magnetic force will be much stronger than that of isotropic magnets. In practical applications, sintered NDFEB and samarium cobalt magnets are anisotropic while anisotropic or isotropic cast ALNICO, sintered ferrite, bonded magnets and rubber magnets are very common.

1.1.2 The application of permanent magnet materials

1.1.2.1 Applications based on the principle of electromagnetic force:

fields of speakers, microphones, electricity meters, motors, relays, sensors, switches, motors, servomotors, micro motors, motors, vibration motors, etc.

1.1.2.2 Applications based on the principle of magnetoelectricity:

fields of permanent magnet mechanism vacuum circuit breaker, magnetic latching relay, sensor, and generator.

 1.1.2.3 The main applications based on the principle of magnetic strength:

fields of magnetic separation, magnetic separator, magnetic crane, magnetic machinery, magnetic bearing, concentrator, magnetic separator, magnetic chuck, magnetic seal, magnetic blackboard, combination lock, copier, control thermometers, door and window magnets, luggage magnets, leather magnets, toys magnets, tool magnets, crafts, etc. Other applications: fields of magnetic therapy, magnetized water, magnetic anesthesia, etc.

1.2 Soft magnetic material

Soft magnetic material can achieve the maximum magnetization with the smallest exteal magnetic field, which is a magnetic material with low coercivity and high permeability. It is easy to be magnetized and demagnetize, that is, the magnetic strength will be very strong if in the exteal magnetic field while magnetic strength will become very weak once removing the exteal magnetic field. Its main function is to conduct magnetic strength, convert and transmit electromagnetic energy, which requires higher magnetic permeability and magnetic induction intensity, and a minor hysteresis loop or small loss of magnetic strength. Compared with permanent magnet materials, the smaller the Br and BHC are, the better performance they have.  Magnetic materials like soft ferrite, amorphous nanocrystalline alloy prefer a stronger Bs.

1.2.1 Application of soft magnetic materials

Mainly used in fields of magnetic antennas, inductors, transformers, magnetic heads, earphones, relays, vibrators, TV deflection yokes, cables, delay lines, sensors, microwave absorbing materials, electromagnets, high-frequency acceleration chambers for accelerators, magnetic field probes, and magnetic substrates , magnetic field shielding, high-frequency quenching energy, electromagnetic chuck, magnetic sensitive components (such as magnetocaloric materials as switches), etc.

1.3 Other functional magnetic materials

Other functional magnetic materials mainly refer to materials that achieve specific purposes or functions through some special effects in the magnetic field, mainly including magnetostrictive materials, magnetic recording materials, magnetoresistive materials, magnetic bubble materials, magneto-optical materials and magnetic thin films materials, etc.

2. Safety precautions

2.1 A magnetic waing sign should be posted in any places where a magnetic field exists or the magnetic material is likely to generate a strong magnetic field as the magnetic field is invisible.

2.2 It is very dangerous for people wearing electronic medical equipment such as pacemakers to approach magnetic materials.

Please note that the medical equipment work may be affected by the magnetic field which may place big risk on that people.

2.3 Keep important electronic equipment away from magnetic materials to avoid any accidents or breakdown that happened on meters and control panels which caused by magnetic fields.

3. Conclusion

Overall, people always associate magnetic materials with magnets, but in fact, permanent magnet materials are just essential part of magnetic materials. Magnetic materials also include other non-magnetic materials that can only generate magnetic fields under certain conditions.

May 3,2022 Posted by Mag Spring® – Green magnetic solution expert

TAGS: What are magnets in the world?  magnetic materials，permanent magnet materials，soft magnetic materials