Effect of post sinter annealing on magnetic properties of bulk Sm_2Fe_(17)N_3 sintered magnets

摘要

The Sm_2Fe_(17)N_3 compound has relatively large magnetocrystalline anisotropy and Curie temperature compared to those of Nd_2Fe_(14)B. However, the Sm_2Fe_(17)N_3 phase decomposes to α-Fe and SmN above 550℃ making conventional sintering techniques unsuitable to consolidate these powders. Metal bonding with Zn is widely used to achieve anisotropic dense Sm-Fe-N magnets. However, the coercivity of metal bonded magnets is about 1500 kA/m, which is only 12% of the anisotropy field of the compound. Here we report high coercivity metal bond Sm_2Fe_(17)B_3 magnets processed by mechanical grinding of Sm_2Fe_(17)N_3 and Zn powders followed by spark plasma sintering and post sinter annealing.