Thermal stability of Sm₂Fe₁₇N₃ magnet powders

The time dependence of coercivity of fine Sm₂Fe₁₇N₃ powder compacts exposed in air and in He gas (oxygen-free atmosphere) was investigated at 110°C and 150°C. At 110°C in air, coercivity rapidly decreased within 5 h, reached a minimum at around 5h, and then gradually increased over 1000 h. Similar behavior was observed in the He gas atmosphere, although the minimum coercivity value was higher than that in air exposure. Since the oxygen content was confirmed to be constant, the coercivity minimum behavior is independent of oxidation. The temperature dependence of the anisotropy field, coercivity and saturation magnetization of fine Sm₂Fe₁₇N₃ powder compacts was measured in air at 110°C and analyzed by using Kronmüller's formula. (paper)