Structure and magnetic behaviors of melt-spun SmFeSiB ribbons and their nitrides

摘要

SmFe_(9.3+x)Si_(0.2)B_(0.1) (x=0, 0.5,1.0) ribbons and their nitrides were prepared by melt-spinning, followed by annealing and subsequent nitriding. The structure and magnetic properties have been investigated by means of powder X-ray diffraction, vibrating sample magnetometer and Mossbauer spectroscopy. Riet-veld analysis shows that the augment of Fe content gives rise to an increase of the c/a ratio and cell volume. The increasing amount of Fe atoms occupying the 2e sites results in the change of initial structure. It is indicated that the isomer shift of 3g and 6l atom remains quasi-constant while the 2e atom shows a noticeable increase with the increase of iron content, which further conforms the preferential occupation of excessive Fe atoms at this site. Consistent with Tc, the mean hyperfine field has the highest value of 25.7 T when x=0.5. The hyperfine fields at different Fe sites follow the order H2e ＞ H3g ＞ H6l. The highest curie temperature of 477.68 K and the hyperfine field of 25.7 T in the as-quenched ribbons were obtained when x=0.5. Meanwhile, the highest magnetic properties of H_(cj) =4.31 kOe, (BH)_m=3.5 MGOe in the nitride powders were found.