X-ray-absorption spectral study of the R{sub 2}Fe{sub 17{minus}x}M{sub x} solid solutions (R=Ce,Nd and M=Al,Si)

Journal Article · Mon Sep 01 00:00:00 EDT 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.6100· OSTI ID:542239

Vandormael, D; Grandjean, F ^[1]; Briois, V ^[2]; Middleton, D P ^[3]; Buschow, K H ^[4]; Long, G J ^[5]

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1. Institute of Physics, B5, University of Liege, B-4000 Sart-Tilman (Belgium)
2. Laboratoire pour lUtilisation du Rayonnement Electromagnetique, Batiment 209D, Universite Paris-Sud, F-91405 Orsay (France)
3. Philips Research Laboratories, NL-5600 JA Eindhoven (the Netherlands)
4. Van der Waals-Zeeman Institute, University of Amsterdam, NL-1018 XE Amsterdam (the Netherlands)
5. Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65409-0010 (United States)

The x-ray-absorption near-edge structure (XANES) spectra obtained at the cerium L{sub III} edge of the Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} solid solutions and Ce{sub 2}Fe{sub 14}Si{sub 3} show two absorption peaks characteristic of the 4f{sup 1} and 4f{sup 0} 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 Gaussian-broadened 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 Ce{sub 2}Fe{sub 17{minus}x}Al{sub 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 Ce{sub 2}Fe{sub 14}Si{sub 3} is not determined by steric 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{sub III}-edge XANES spectra of the Nd{sub 2}Fe{sub 17{minus}x}Al{sub 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 edge of the Ce{sub 2}Fe{sub 17{minus}x}Al{sub x} and Nd{sub 2}Fe{sub 17{minus}x}Al{sub x} solid solutions show changes in 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. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 542239
• Journal Information: Physical Review, B: Condensed Matter, Vol. 56, Issue 10; Other Information: PBD: Sep 1997
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
CERIUM COMPOUNDS
X-RAY SPECTRA
NEODYMIUM COMPOUNDS
ALUMINIUM COMPOUNDS
SILICON COMPOUNDS
IRON ALLOYS
CERIUM ALLOYS
SILICON ALLOYS
ALUMINIUM ALLOYS
NEODYMIUM ALLOYS
INTERMETALLIC COMPOUNDS
SOLID SOLUTIONS
CHEMICAL BONDS
VALENCE
CERIUM
SYNCHROTRON RADIATION
MAGNETIC MATERIALS
CHEMICAL COMPOSITION
ELECTRONIC STRUCTURE