Rare earth permanent NdFeB magnets has the strongest magnetism nowadays. It does not only has high remanence, high coercivity, high energy product, and high-functional, but also it can processed into a variety of sizes easily. Now, it is widely used in avigation, spaceflight, electron, electrical sound, electrical machinery, apparatus, meters, medical technology, and especially apply to develop high-performance, small and light replacements.

The Alnico (Aluminum, Nickel, Cobalt) family was introduced in the 1930’s. It’s characterized by excellent temperature stability, high residual induction, relatively high energies and resistant to corrosion. These were the first materials specifically designed for permanent magnets to be used in meters and instruments commercially. Alnico is available in both cast and sintered forms. Sintered Alnico offer slightly lower magnetic properties but better mechanical characteristics than cast Alnico. These materials are brittle, hard and cannot effectively be machined by conventional techniques other than by grinding.

The hard ferrite is manufactured with SrO or BaO and Fe2O3 by ceramic process,it is also called ceramic mangets. Because of its cheaper price, and production process is relatively simple, compared with the prices of their products relatively cheap in terms of other magnets. The main raw materials of ferrite magnets is oxide, so, it could not be eroded due to the impact of chemical substances or the environment (except for acid). Therefore, the surface does not need electroplating treatment. It is mainly used in handicrafts, drawing annex, toys, motor, loud speakers.