Effect of Fe content on structural and magnetic properties of SmCo4−xFexB alloys

The phase formation and magnetic behavior of SmCo4−xFexB (x = 0, 0.25, 0.5, 0.75, 1 and 2) produced by melt spinning have been investigated. At x = 0, melt spinning resulted in the formation of the SmCo4B phase and an ultrahigh coercivity of 44 kOe at 300 K. Fe substitution resulted in the formation of an amorphous structure along with the Sm(Co,Fe)4B phase during melt spinning. A single Sm(Co,Fe)4B phase was observed after crystallization when x < 1, while Sm(Co,Fe)4B and Sm2(Co,Fe)17By were observed when x ⩾ 1. Hysteresis loops at x < 1 displayed a single-phase magnetic behavior which was absent when x ⩾ 1. In the crystallized Fe-containing materials, an increase in both coercivity and magnetization with increasing Fe content was observed until x = 1. Initial magnetization curves revealed nucleation-controlled behavior at x < 1 and a combination of nucleation and domain wall pinning at x = 1 and x = 2. The average grain size for the annealed SmCo4−xFexB samples measured from TEM micrographs was 110 nm for both x = 0.5 and x = 1 and 90 nm for x = 2.