Phase analysis and magnetic properties of RE2(Fe1-xMox)17 (RE=Nd, Gd) alloys

The structural and magnetic properties of RE2(Fe1-xMox)(17) alloys (RE= Gd and Nd; 0.00 less than or equal to x less than or equal to 0.10) have been investigated by X-ray diffraction and magnetic techniques. The samples were prepared by are melting and annealed at 1373 K. The study of thermomagnetic analysis curves and XRD patterns reveals that the phase composition is quite similar for both alloy systems. The Rietveld method was employed to determine the phase composition and lattice parameters. In the 0.00 less than or equal to x less than or equal to 0.03 composition range, the samples are almost single phase with the rhombohedral Th2Zn17-type crystal structure; with the substitution of Fe for Mo a slight lattice expansion is induced. For higher Mo concentrations, this phase co-exists with a certain amount of spurious phases: a) 1:12-type compound for RE= Nd, and b) 1.12- and 3:29-type compounds for RE= Gd. This suggests that the solubility of Mo in 2:17 is low. The Curie temperatures do not show remarkable variations when Fe is replaced by Mo. In Gd-2(Fe,Mo)(17), the increase in the Mo content leads to a decrease in the saturation magnetization values while in Nd-2(Fe,Mo)(17) a smooth increase is observed. A possible explanation for this behavior, in terms of a different site occupancy of Mo atoms in the structure, is discussed.