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Neutron diffraction studies of the atomic and magnetic structures of Ho/sub 6/Mn/sub 23/, Ho/sub 6/Mn/sub 23/D/sub 22/ and some Y/sub 6/(Fe/sub 1-x/Al/sub x/)/sub 23/ compounds

Thesis/Dissertation ·
OSTI ID:7225768
Neutron diffraction studies of three Y/sub 6/(Fe/sub 1-x/Al/sub x/)/sub 23/ compound (x = 0.05, 0.10, 0.15) at 523 and 77K reveal substantial preferential atomic ordering of Fe and Al atoms on the four crystallographic sites. Fe atoms prefer to occupy the f/sub 1/ site and Al atoms the f/sub 2/ site. The site preferences are explained on the basis of the comparative atomic volumes and the nearest neighbor distances. At 77 K the compounds are ferromagnetic. The Fe atoms exhibit different magnetic moments on the four sites. Neutron diffraction experiments were also performed on Ho/sub 6/Mn/sub 23/. At 77 K it is found to have a face-centered cubic crystal structure and a non-collinear magnetic structure, with the Ho moments tilted at an angle of 33.4/sup 0/ to the Mn moments. Powder neutron diffraction data for Ho/sub 6/Mn/sub 23/D/sub 22/ were analyzed by a modified Rietveld technique. At 298 K the space group is Fm3m; at 9K, P4/mmm. At 298K the deuteriums occupy the a, f/sub 3/, j, and k sites, in agreement with the predictions of Westlake's model. At 9K, a noncollinear antiferromagnetic structure is found.
Research Organization:
Missouri Univ., Rolla (USA)
OSTI ID:
7225768
Country of Publication:
United States
Language:
English