Atomic defects in the structural layers of hexagonal Er2Fe17

X-ray and neutron powder diffraction has been carried out on the compound Er2Fe17 which crystallizes in the Th2Ni17 type (P63/mmc) hexagonal phase. H - 2K = 3n L = 2n are the strongest reflection in both x-ray and neutron powder diffraction pattern (for example 302) showing the ordered transition metal substitutions on the planes perpendicular to c axis resulting in ABABAB hor-ellipsis sequence of basic structural layers. However, H - K ≠ 3n L = 2n type reflections have been observed with sizable intensities in the neutron diffraction spectrum. The very appearance of these reflections indicates that there is less than complete order on A and B chains, and some random substitutions take place on C chains, resulting in Fe-rich side of the 2:17 stoichiometry. These defects in the stacking sequences of hexagonal layers linked with the fine scale metallurgical microstructure have profound influence on the magnetic properties required in the design of new hard magnetic materials. 7 figs