Title

A Magnetic Neutron Diffraction, and Mössbauer Spectral Study of the Ce₂Fe₁₇₋ₓAlₓ Solid Solutions

Abstract

The magnetic properties of a series of Ce2Fe17-xAlx solid solutions with x equal to 0.00, 0.88, 2.06, 2.81, 3.98, 5.15, 6.08, 7.21, 8.20, 9.08, 9.84, and 10.62 have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. The compounds crystallize in the rhombohedral Th2Zn17-type structure. Magnetization studies indicate that the Curie temperature increases uniformly from 238 K for Ce2Fe17 to 384 K for Ce2Fe14Al3 and then decreases at higher aluminum content. Powder neutron diffraction results, obtained at 295 K, indicate that aluminum avoids the 9d site for all x values and preferentially occupies the 18h site at low aluminum content. Aluminum shows a marked preference for the 6c site for x>6. The room-temperature iron magnetic moments increase from x = 0 to 2 and then decrease for x>2. The Mössbauer spectra have been fit with a binomial distribution of the near-neighbor environments in terms of a maximum hyperfine field, Hmax, for an iron with zero aluminum near neighbors, and a decremental field, ΔH, per aluminum near neighbor. The compositional dependence of the decremental field indicates the influence of aluminum on the long-range magnetic ordering in the compound. The compositional dependence of the weighted average maximum hyperfine fields and the weighted average isomer shifts in Ce2Fe17-xAlx may be understood in terms of a mixing of the 3d conduction band electrons with the 3p valence band electrons of aluminum, a mixing which is more extensive than that associated with silicon in the Ce2Fe17-xSix solid solutions. We conclude that this mixing has a larger influence on the magnetic properties of these solid solutions than does the presence of a short iron-iron bond or the expansion or contraction of the lattice parameters and unit cell volume. © 1996 American Institute of Physics.

Department(s)

Chemistry

Second Department

Physics

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1996 American Institute of Physics (AIP), All rights reserved.


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