Structure and magnetic properties of melt-spun Sm-Fe-Nb ribbons and their nitrides

SmFe10-x Nb (x) (x = 0, 0.1, 0.2, 0.3) ribbons and their nitrides were prepared by melt-spinning, followed by annealing and subsequent nitriding. The structure and magnetic properties were investigated by means of X-ray diffraction (XRD) using the Rietveld method, vibrating sample magnetometer (VSM), transmission electron microscope (TEM) and Mossbauer spectroscopy. XRD analysis shows that the addition of Nb can impede the precipitation of Sm2Fe17 and alpha-Fe phases and the Nb atoms occupy 2e site in the alloys. At 300 K, the mean hyperfine fields of 2e site are 29.58 T with Nb doping at x = 0.1 and the corresponding Curie temperature is 552 K. The optimal properties of remanence of B (r) = 0.9 T, intrinsic coercivity of H (cj) = 741.5 kA center dot m(-1), and maximum magnetic energy product of (BH)(max) = 124.2 kJ center dot m(-3) are gained at x = 0.10 in the nitrides.