Neodymium magnet is a tetragonal crystal (Nd2Fe 14B) composed of neodymium, iron and boron. 1982, Masato Sagawa of Sumitomo Special Metals Company discovered neodymium magnet. The magnetic energy product (BHmax) of this magnet was larger than that of the largest samarium cobalt magnet in the world at that time. [24] Later, Sumitomo Special Metals Company developed the powder metallurgy process, and General Motors Company developed the melt spinning process, which can prepare neodymium magnets. [25] This kind of magnet is the strongest permanent magnet at present, and it is also the most commonly used rare earth magnet, which is widely used in electronic products, such as hard disks, mobile phones, headphones, battery-powered tools and so on.
In order to avoid corrosion damage, it is necessary to protect the surface of permanent magnet materials, such as electroplating gold, nickel, zinc and tin, and spraying epoxy resin on the surface. [26]