Evidence for rattling behavior of the filler atom(L)in the filled skutteruditesLT4X12

D. Cao

¹

,

F. Bridges

²

,

Paul Chesler

³

et al.

Abstract

Extended x-ray absorption fine structure (EXAFS) measurements have been carried out at the L K-or L III -edges (L = Ce, Eu, and Yb) and T K-edges (T = Fe and Ru) for a series of filled skutterudite materials, LT 4 X 12 (X = P and Sb). The high correlated Debye temperature ͑⌰ D ϳ 400 K͒ obtained for the T-X peak indicates that the T 4 X 12 framework is relatively stiff. In contrast, the low Einstein temperature ͑⌰ E ϳ 100 K͒ 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 4 Sb 12 than in CeFe 4 Sb 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 2 ͑T͒ 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.

Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1−xGdGarcia1, Venegas2, Pagliuso3 et al. 2011Phys. Rev. B

“…14 Also, evidences for rattling of the Yb 3+ and Ce 4+ ions were found in ESR 11 and extended x-ray absorption fine structure (EXAFS) 17 experiments, respectively. The aim of this work is to learn if the presence of thermally activated conduction-carriers and rattling of the R ions can be observed by the ESR technique.…”

Eu2+spin dynamics in the filled skutterudites EuM4Sb12(Garcia1, Adriano2, Cabrera3 et al. 2011Phys. Rev. B4060View full textAdd to dashboardCite

“…In these compounds, the filler Eu atom is known to rattle with Einstein temperatures θ E = 78 K (T = Ru) and θ E = 74 K (T = Os) 15,18 . These temperatures are very similar to those where ∆H approaches its maximum before starting to narrow.…”

“…Close investigation of the T = Fe system indicates that, in fact, a ferrimagnetic transition takes place at T C = 90 K, as a consequence of an antiferromagnetic coupling of the Eu and Fe moments 16,17 . The rattling behavior of the Eu 2+ ions was studied by structure refinement of x-ray diffraction measurements 15 and also by extended x-ray fine structure (EXAFS) measurements 18 . The results obtained from both methods are in close agreement.…”

Collapse of the Gd3+ ESR fine structure throughout the coherent temperature of the Gd-doped Kondo Semiconductor CeFeVenegas1, Garcia2, García3 et al. 2016Phys. Rev. B80100View full textAdd to dashboardCite

“…, as probed by EXAFS studies [30]. Surprisingly, this temperature scale is about the same as the temperature * 150 T ≈ K, which marks the loss of coherence of heavy-fermion behavior, obtained from resistance experiments [20].…”

“…This behavior is certainly related to the insulator-to-metal crossover induced by the loss of coherence, and exhibits the sensitivity of EPR experiments to probe such a remarkable effect. In this paper, we present numerical simulations for the collapse of the CeFe P as a Kondosemiconductor with a relatively large and T-dependent pseudogap [1,30,32]. This Tdependence originates from many-body correlation effects in a Kondo lattice.…”