A Magnetic, Neutron Diffraction, and Mössbauer Spectral Study of Nd₂Fe₁₅Ga₂ and the Tb₂Fe₁₇₋ₓGaₓ Solid Solutions

Author

Zhong Bo Hu
William B. Yelon, Missouri University of Science and Technology
Sanjay R. Mishra
Gary J. Long, Missouri University of Science and TechnologyFollow
Oran Allan Pringle, Missouri University of Science and TechnologyFollow
D. P. Middleton
K. H. J. Buschow
Fernande Grandjean, Missouri University of Science and TechnologyFollow

Abstract

An x-ray diffraction study of the substitution of gallium in Tb ₂Fe₁₇ to form the Tb₂Fe_17-xGa_x solid solutions indicates that the compounds adopt the rhombohedral Th₂Zn₁₇ structure. The unit cell volume and the a-axis lattice parameter increase linearly with increasing gallium content. The c-axis lattice parameter increases linearly from x=0 to 6 and then decreases between x=7 and 8. Magnetic studies show the Curie temperature increases by ~150° above that of Tb₂Fe₁₇ to reach a maximum between x=3 and 4, and then decreases with further increases in x. Neutron diffraction studies of Nd₂Fe₁₅Ga₂ and Tb ₂Fe_17-xGa_x, with x equal to 5, 6, and 8, indicate that the gallium completely avoids the 9d site, occupies the 6c "dumbell" site only at high values of x and strongly prefers the 18f site at high values of x. The magnetic neutron scattering indicates both that the terbium sublattice magnetization couples antiferromagnetically with the iron sublattice and that there is a change in easy magnetization direction from planar to axial with increasing gallium concentration. This change in easy magnetization direction is explained in terms of a sign reversal of the second-order crystal field parameter, A⁰₂, the most important parameter responsible for determining the terbium sublattice anisotropy. The Mössbauer effect spectra indicate a larger room-temperature average hyperfine field at the iron site in the Tb₂Fe _17-xGa_x solid solutions than in several related R ₂Fe₁₇ compounds. The large observed increase in the isomer shift with increasing gallium content results from interatomic charge transfer and intraatomic s-d charge redistribution in the presence of gallium.

Recommended Citation

Z. B. Hu et al., "A Magnetic, Neutron Diffraction, and Mössbauer Spectral Study of Nd₂Fe₁₅Ga₂ and the Tb₂Fe₁₇₋ₓGaₓ Solid Solutions," Journal of Applied Physics, vol. 76, no. 1, pp. 443 - 450, American Institute of Physics (AIP) Publishing, Jul 1994.

The definitive version is available at https://doi.org/10.1063/1.357094

Department(s)

Physics

Second Department

Chemistry

International Standard Serial Number (ISSN)

0021-8979

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 1994 American Institute of Physics (AIP) Publishing, All rights reserved.

Publication Date

01 Jul 1994