Coercivity of Sm2Fe17N3 particles prepared by mechanically grinding without exposing in air

As a first step for clarifying coercivity mechanism in high-performance permanent magnets, the effect of particle size on coercivity in Sm₂Fe₁₇N₃ was studied by mechanically grinding method without exposing in air. The coercivity increases with increasing the grinding time, reaches a maximum value of 1.23 T at grinding time for 60 min and gradually decreases beyond 90 min grinding, The resultant maximum energy product reaches up to 329 kJ/m ³ for 60 min grinding. However, the coercivity of 1.23 T is still too small compared with the anisotropy field, suggesting that the surface effect controls the coercive force in this system, rather than the size effect