Experimental determination of the phonon density of states in filled skutterudites: evidence for a localized mode of the filling atom

Abstract

The generalized density of states of LaFe₄Sb₁₂ and CeFe₄Sb₁₂ has been determined by inelastic neutron scattering and its main features are found to be in agreement with recently published calculations (J. L. Feldman, D. L. Singh, C. Kendziora, D. Mandrus and B. C. Sales, Phys. Rev. B, 2003, 68, 094301). In both compounds a localized vibrational contribution appears superposed on the low-energy Debye response. The distinct inelastic response of La in LaFe₄Sb₁₂ is obtained by subtraction of the data for the Ce filled compound and it shows even more clearly the resolution limited peak at 7 meV, attributed to the localized mode of La-atoms.