Permanent magnet materials are widely used in various motors in industries such as automobiles, home appliances, energy, machinery, medical treatment, and aerospace, as well as components that require strong gap magnetic fields. Magnetic materials are closely related to all aspects of information technology, automation, mechatronics, national defense, and national economy, and have irreplaceable advantages in many fields. Magnetic materials are generally Fe, Co, Ni elements and their alloys, rare earth elements and their alloys, and some Mn compounds. Magnetic materials are divided into soft magnetic materials and hard magnetic materials according to the degree of difficulty of their magnetization. Among them, soft magnetic materials are relatively easy to magnetize and demagnetize compared to permanent magnetic materials. Their main functions are magnetic permeability and electromagnetic Energy conversion and transmission; hard magnetic materials are also known as permanent magnetic materials. After being magnetized by an external magnetic field, even under the action of a considerable reverse magnetic field, they can still maintain the magnetism of one or most of the original magnetization directions, and have electrical signal conversion , The electrical energy-mechanical energy conversion function is widely used in various motors in industries such as automobiles, home appliances, energy, machinery, medical, aerospace and other industries, as well as components that need to generate a strong gap magnetic field.
Permanent magnet materials can be divided into three categories: rare earth permanent magnets, ferrite permanent magnets and other permanent magnets. Among them, rare earth permanent magnet materials have continued to develop at a high speed since the 1960s. According to the time sequence of their development and application, they can be divided into four generations: the first generation is RECo5 series materials represented by SmCo5; the second generation is RECo17 series represented by Sm2Co17 Magnet; the third generation is a neodymium iron boron (NdFeB) magnetic material that was successfully developed in the early 1980s. Because it is an Fe-based rare earth material, it has a lower price and excellent performance. It quickly replaced RECo17 in many fields Type magnets are currently the most widely used rare earth permanent magnet materials, and the fourth generation is iron-nitrogen (Re-Fe-N) and iron-carbon (Re-Fe-C) systems, which are still in the experimental development stage, or require dozens of It will take a relatively long time to realize large-scale production and application.