Order-disorder effects in nitrided Sm-Fe permanent magnets

Rapidly solidified Sm11Fe89 was observed to form partially ordered Sm2Fe17. The ordering increased systematically with annealing temperature, reaching an order parameter of 0.8 after annealing at 950 degrees C for 15 min. The coercivity of the corresponding interstitial compound Sm2Fe17Nx varied wit h annealing temperature and thus order parameter. The coercivity reached a maximum for an order parameter of 0.45-5, then dramatically decreased as th e order increased. This behavior is characteristic of demagnetization contr olled by domain wall pinning by antiphase boundaries. (C) 2000 American Ins titute of Physics. [S0021-8979(00)91008-9].