Raman Scattering Investigation of Skutterudite Compounds

Raman scattering spectra have been measured for the unfilled skutterudite CoP3 and for the filled skutterudites RT4X12 (R= La, Ce, Pr and Nd, T=Fe and Os, and X=Sb and P). For the P‐skutterudite, the energies of two Ag phonons and one Eg phonon decrease with rare‐earth filling, while, for the Sb‐skutterudite, the energies of the observed phonons do not change significantly. In order to clarify this filling effect microscopically, a normal mode analysis has been performed using a GF matrix method. The following differences due to the filling effect have been found for the P‐ and Sb‐skutterudites: the interaction between pnictogens on the cage becomes weaker for the P‐skutterudite, while it does not change significantly for the Sb case.