Elastic properties of filled-Skutterudite compounds probed by Mössbauer nuclei

We have carried out Mossbauer spectroscopy and nuclear resonant inelastic scattering to elucidate the lattice dynamics in fi.lled-Skutterudite compounds, especially phosphides. The second-order Doppler shift obeys the Debye model in RFe4P12 Nuclear quadrupole interaction reveals an unusual temperature dependence in these compounds. An anomaly is observed in 57Fe nuclear resonant inelastic scattering of these compounds. The energy where the anomaly observed in SmFe4P12 agrees with the phonon excitation energy observed by 149Sm nuclear resonant inelastic scattering. We have also performed the 99Ru Mossbauer measurements SmRu4P12.