Magnetic properties of SmCo7/Co and Sm(Co,Fe)7/α-(Fe,Co) nanocomposite magnets prepared by magnetic annealing

The effect of applying a magnetic field during the crystallization process of mechanically milled SmCo_9.5 and Sm(Co_0.88Fe_0.12)_9.5 alloys on the nanostructure, exchange coupling, and magnetic properties has been studied. Compared with samples annealed without the magnetic field, there was a noticeable improvement in the intrinsic coercivity _iH_c, the remanence B_r, and the maximum magnetic energy product (BH)_max for SmCo_9.5 and Sm(Co_0.88Fe_0.12)_9.5 alloys annealed in a 10 kOe field. An improvement of 31.5% of (BH)_max was obtained for SmCo_9.5 alloy after the magnetic annealing. Better rectangularity of the demagnetization curves was also observed for SmCo_9.5 and Sm(Co_0.88Fe_0.12)_9.5 alloys after the magnetic annealing. The improvement in the magnetic properties after magnetic annealing is considered to be the result of enhanced exchange coupling, resulting from modifications of nanostructure induced by the magnetic field during the crystallization process of the mechanically milled alloys in a nearly perfect amorphous state.