Low temperature coefficient Neodymium series can be used in sealed conditions at least 20 years. The Br value α(20～MT) reaches -0.095%/℃. Compared with conventional temperature coefficient magnets, low temperature coefficient magnets have better demagnetization resistance and magnetic flux density consistency For example, 35UHT low temperature coefficient magnet is baked at 180 ℃ for 200hrs, and the magnetic power loss rate is less than 1%. At the same time, the magnet also has low weight loss characteristics. At 130 ℃, 100% RH, 2.7 atm, 168hrs, the weight loss rate is less than 0.5 mg/cm². After passivation of the magnet surface, the magnet can stably serve for more than 20 years in a sealed environment.