High temperature resistant magnets are also called magnetic steel. Magnetic steel is now mainly divided into two categories, one is soft magnet and the other is permanent magnet; permanent magnets include silicon steel sheets and soft high temperature resistant magnetic cores; hard magnets include aluminum nickel cobalt, samarium cobalt, ferrite and neodymium iron boron. Among them, the most expensive is samarium cobalt magnet, the cheapest is ferrite magnet, and the highest performance is neodymium iron boron magnet, but the most stable performance and the best temperature coefficient are aluminum nickel cobalt magnets. Users can choose different hard magnetic products according to different needs. So how to define the performance of high temperature resistant magnets? There are mainly three performance parameters to determine: Remanence Br: After the permanent magnet is magnetized to technical saturation and the external magnetic field is removed, the retained Br is called the residual magnetic induction