EXAFS study of filled skutterudites RT4Sb12(R:La,Ce, Pr,Nd,Sm, T:Fe,Ru,Os)

Abstract

The filled skutterudites RT4X12 (R: rare-earth, T: transition metal, X: pnictogen) show a variety of intriguing features by changing the combination of R, T, and X. Among them, some compounds shows characteristic feature called "rattling" that is considered as anharmonic oscillation or off-centered motion of rare-earth ions accommodated in the icosahedron cages made from pnictogen and "rattling" is suggested to contribute to the various features of this system. We applied extended X-ray absorption fine structure (EXAFS) on this system to clarify the microscopic mechanism of "rattling" motion [1]. Temperature dependence of EXAFS thermal (Debye-Waller) factors of R-Sb and T-Sb atomic pairs were analyzed by Einstein model. Thermal oscillation and static distortion are analyzed independently. From this study, we could know systematic information about "rattling" as a large amplitude oscillation of rare-earth ions and static distortion that has two types of cage space dependence. © 2009 IOP Publishing Ltd.