Evidence for rattling behavior of the filler atom (L) in the filled skutterudites LT{sub 4}X{sub 12} (L=Ce,Eu,Yb; T=Fe,Ru; X=P,Sb) from EXAFS studies

Journal Article · Wed Sep 01 00:00:00 EDT 2004 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.70.094109· OSTI ID:20664883

Cao, D ^[1]; Bridges, F; Chesler, P; Bushart, S ^[1]; Bauer, E D; Maple, M B ^[2]

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1. Physics Deparment, University of California, Santa Cruz, California 95064 (United States)
2. Department of Physics and Institute of Pure and Applied Physical Science, University of California, San Diego, La Jolla, California 92093 (United States)

Extended x-ray absorption fine structure (EXAFS) measurements have been carried out at the L K- or L{sub III}-edges (L=Ce, Eu, and Yb) and T K-edges (T=Fe and Ru) for a series of filled skutterudite materials, LT{sub 4}X{sub 12} (X=P and Sb). The high correlated Debye temperature ({theta}{sub D}{approx}400 K) obtained for the T-X peak indicates that the T{sub 4}X{sub 12} framework is relatively stiff. In contrast, the low Einstein temperature ({theta}{sub E}{approx}100 K) obtained for the L-X or T-L pairs strongly supports the concept of a 'rattling' local mode behavior for the L ions. The analysis also indicates that this rattling frequency is much smaller in the antimonide skutterudites than in the phosphide ones, and smaller in CeOs{sub 4}Sb{sub 12} than in CeFe{sub 4}Sb{sub 12}. Both results indicate that the larger the void within which the Ce atom is located, the lower the rattling frequency. In addition, for some systems in which the signal-to-noise for {sigma}{sup 2}(T) is high, a fit can be made to extract the reduced mass of the rattling atom; in these cases the obtained reduced mass is close to but slightly below that of the rattler atom mass-clear evidence of a localized mode inside a stiff but not rigid cage. Finally, no clear evidence for any off-center displacement of the filler ions was found in these materials.

• OSTI ID: 20664883
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 70, Issue 9; Other Information: DOI: 10.1103/PhysRevB.70.094109; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
CERIUM COMPOUNDS
DEBYE TEMPERATURE
EUROPIUM COMPOUNDS
FINE STRUCTURE
IRON COMPOUNDS
RUTHENIUM COMPOUNDS
VOIDS
X RADIATION
X-RAY SPECTROSCOPY
YTTERBIUM COMPOUNDS