Structure and magnetic properties of TbCu 7 -type melt-spun Sm–Fe–B alloys

The melt-spun SmFe 12 B x ( x = 0, 0.50, 0.75, 1.00, 1.25 and 1.50) ribbons were prepared at 40 m·s −1 , and their structure and magnetic properties were studied by powder X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and transmission electron microscopy (TEM). XRD results indicate that SmFe 12 B x alloys with 0.50 ≤ x ≤ 1.00 are composed of single-phase TbCu 7 -type structure. Moreover, it is found that the boron addition can inhibit the emergence of soft magnetic phase α-Fe and result in the increase in the axial ratio c / a . After annealing at 650 °C for 0.5 h, the metastable phase TbCu 7 initially decomposes into the stable phase Sm 2 Fe 14 B (Nd 2 Fe 14 B-type) and α-Fe. The value of magnetic moment per Fe atom increases slightly from 1.75 μ B for boron-free sample to 1.80 μ B for the x = 0.75 sample and then decreases again. In addition, the best magnetic properties of maximum energy product [( BH ) max ] of 14.56 kJ·m −3 , coercivity ( H cj ) of 172.6 kA·m −1 and remanence ( B r ) of 0.45T are obtained for the SmFe 12 B 1.00 alloy. Based on transmission electron microscopy (TEM) results, the average size of grains is around 197 nm for B-free sample and decreases to 95 nm for x = 1.00 sample, indicating that the addition of boron can refine grains.