X-ray and Mossbauer studies of Sm-Fe-Nb(Zr) (2:17:2) alloys and their nitrides

Sm-Fe and Sm-Fe-(Nb or Zr) alloys, with stoichiometry RE:TM = 2:17 were prepared in ribbon form, using the melt spinning technique. The samples then were annealed and nitrated. X-ray diffraction and Mossbauer spectroscopy were used to study the samples. The presence of Nb(Zr) atoms stabilizes the TbCu7 structure, while the samples without substitutions crystallize in the Th2Zn17-type structure. The hyperfine parameters for the corresponding phases are deduced from analysis of Mossbauer spectra in the temperature range 15-300 K. At 300 K the mean hyperfine fields are 241 and 219 kOe for the Nb and Zr phases, respectively. The Curie temperature of Sm2Fe17 is higher than that of the intermetallic compound Sm2Fe17 prepared by the arc melting technique, and the Curie temperatures of the TbCu7-type phases are in the range 200-230°C. Remarkable enhancements in the coercive fields of the 1:7 nitride products are observed.