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 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.