X-ray and intrinsic magnetic properties of nanocrystalline Sm2(Fe,M)17 (M = Si, Ga, Co, Cr, Zr or Mo)

The structure and magnetic properties of ball-milled and subsequently annealed Sm2Fe17–xMx compounds (M = Si, Ga, Co, Cr, Zr, Mo, for x = 2) were investigated by X-ray diffraction coupled with magnetic measurements and Mössbauer spectroscopy. Rietveld analysis have shown that all these samples crystallize in the Th2Zn17 type rhombohedral structure. The substituting elements Si, Ga, Co occupy the 18h atom site, while Cr, Zr, Mo prefer the 6c site. Mössbauer studies corroborate these results. The X-ray analysis cannot solve the possible M atom distribution over Fe atom sites when atomic factors of Fe and M are close. Mössbauer spectroscopy appears as the efficient tool to raise this ambiguity. The Curie temperature increases upon Zr and Cr substitution reaching a maximum for x = 1, then decreases because of magnetic dilution.