A structural, magnetic, and Mössbauer study of the Dy2Fe17-xNbx solid solutions
The single-phase intermetallic compounds of refractory metal Nb doped Dy2Fe17-xNbx were prepared by arc melting. The substitution of Nb in the Dy2Fe17-x compound was found to have an important effect on their structure and magnetic properties. The Rietveld analysis of X-ray diffraction data shows that Dy2Fe17-xNbx (x=0"“1.5) solid solutions crystallize with the Th2Ni17 structure. The lattice parameters obtained from Rietveld refinement show that the unit cell volume of Dy2Fe17-xNbx increases linearly with increasing Nb concentration up to x=1. The solubility of Nb was found to be limited to x~1. The substitutional Nb atoms occupied all four sites in the order 12j > 12k > 6g > 4f of a Th2Ni17 structure. The Curie temperature (Tc) was found to be Nb content dependent. The Tc first increased and then decreased with increasing Nb content x, attaining a maximum value of 460 K at around x=1, which is 78 K higher than that of Dy2Fe17. The saturation magnetization decreased linearly with increasing Nb content from 69 emu/g for x=0 to 38 emu/g for x=1.5. 57Fe Mössbauer spectra show the presence of DyFe3 and NbFe2 phases at a higher Nb content x≥1. The hyperfine field values of 4f site first increased up to x=1 and then decreased at higher Nb content.