Anomalous thermal expansion in Nd{sub 2}Fe{sub 17{minus}{delta}}Ga{sub {delta}} ({delta}=0{endash}2)
- Materials Sciences Division, Lawrence Berkeley National Laboratory, and Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720-1760 (United States)
- Department of Physics, Centre for the Physics of Materials, McGill University, 3600 University Street, Montreal, Quebec H3A 2T8 (Canada)
- Neutron and Condensed Matter Science, AECL, Chalk River, Ontario K0J 1P0 (Canada)
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
- Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720-1760 (United States)
In Nd{sub 2}Fe{sub 17{minus}{delta}}Ga{sub {delta}} ({delta}=0;0.5;1;1.5;2), Ga substitutes for Fe without changing the crystal structure. Neutron diffraction measurements show that Ga preferentially substitutes for Fe in the 18h sites only. The magnetic moments in Nd{sub 2}Fe{sub 17{minus}{delta}}Ga{sub {delta}}, below the Curie temperature, T{sub c}, are found to be in the basal plane. Below T{sub c} the unit cell constant, {ital c}, decreases with increasing temperature for Nd{sub 2}Fe{sub 17{minus}{delta}}Ga{sub {delta}} ({delta}{le}1). For Nd{sub 2}Fe{sub 17{minus}{delta}}Ga{sub {delta}} ({delta}{gt}1), the thermal expansion coefficient changes sign and becomes positive for Nd{sub 2}Fe{sub 15}Ga{sub 2}. The relative decrease in the Fe(6c){endash}Fe(6c) distance is twice as large as the decrease in the {ital c} axis below T{sub c}. Below T{sub c}, the Fe(6c){endash}Fe(6c) distance decreases with an increase in the Ga concentration, while above T{sub c} the Fe(6c){endash}Fe(6c) distances are found to be independent on Ga concentration indicating that the presence of Ga decreases the negative exchange coupling between Fe atoms. {copyright} {ital 1999 American Institute of Physics.}
- OSTI ID:
- 347046
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 85; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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