X-ray-Absorption Spectral Study of the R₂Fe₁₇₋ₓMₓ Solid Solutions (R=Ce, Nd and M=Al, Si)

Author

Denis Vandormael
Fernande Grandjean, Missouri University of Science and TechnologyFollow
Valérie Briois
D. P. Middleton
K. H. Buschow
Gary J. Long, Missouri University of Science and TechnologyFollow

Abstract

The x-ray-absorption near-edge structure (XANES) spectra obtained at the cerium L_III edge of the Ce₂Fe_17-xAl_x solid solutions and Ce₂Fe₁₄Si₃, show two absorption peaks characteristic of the 4f¹ and 4f⁰ configurations of cerium, peaks which indicate that cerium is in a mixed valent state in these compounds. All the XANES spectra have been consistently and excellently fit with one sigmoidal function and two Gaussianbroadened Lorentzian functions. The cerium spectroscopic valence obtained from the relative areas of the two peaks decreases from 3.64 to 3.43 between x=0 and 9 in Ce₂Fe_17-x,Al_x, and correlates linearly with the cerium site volume This correlation confirms that the cerium valence is strongly dependent upon steric effects. In contrast the cerium valence obtained from the XANES spectrum of Ce₂Fe₁₄Si₃ is not determined by stenc effects and indicates, in agreement with other measurements and calculations, that silicon is more covalently bonded with its near-neighbor cerium atoms than is aluminum. The neodymium L_III,-edge XANES spectra of the Nd₂Fe_17-x Al_x solid solutions, where x is 0, 3, and 8, reveal the presence of only trivalent neodymium and an increase of the empty 5d state density when aluminum is substituted in place of iron. XANES measurements at the iron K edee of the Ce₂Fe_17-xAl_x, and Nd₂Fe_17-1Al_x, solid solutions show changes m the relative intensity of the multiple scattering peaks, changes which are related to the changing composition of the first three neighbor shells with increasing aluminum content.

Recommended Citation

D. Vandormael et al., "X-ray-Absorption Spectral Study of the R₂Fe₁₇₋ₓMₓ Solid Solutions (R=Ce, Nd and M=Al, Si)," Physical Review B (Condensed Matter), vol. 56, no. 10, pp. 6100 - 6106, American Physical Society (APS), Sep 1997.

The definitive version is available at https://doi.org/10.1103/PhysRevB.56.6100

Department(s)

Chemistry

International Standard Serial Number (ISSN)

0163-1829

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 1997 American Physical Society (APS), All rights reserved.

Publication Date

01 Sep 1997