CRYSTAL AND MAGNETIC-STRUCTURE OF ER2(COXFE1-X)17 COMPOUNDS

Room-temperature neutron-diffraction spectra on compositions x=0.0, 0.20, 0.40, 0.55, 0.80, and 1.0 have been obtained and analyzed for crystal and magnetic structures. The crystal structures deviate from the ideal Th 2Ni17 structures, as has been observed in the other hexagonal 2-17 materials. Structure analysis from the nuclear intensities at 350 K leads to a precise stoichiometry of Er1.91Fe18.25 in Er2Fe17. Because of the high Tc of the Co-rich compounds, the Er atoms align at relatively high temperature and the axial Er anisotropy dominates at room temperature. Only at x=0.4 composition is a spin reorientation from planar to axial observed below room temperature. The f site, which is analogous to the c site in rhombohedral Th 2Zn17 and the j2 site in Re 2Fe14B, does not support a moment as large as on the c site and j2 site in respective phases. The moment reduction is probably related to atomic defects on the dumbbell f site.