Dynamics of the Singlet-Triplet System Coupled with Conduction Spins -- Application to Pr Skutterudites

摘要

Dynamics of the singlet-triplet crystalline electric field (CEF) system atfinite temperatures is discussed by use of the non-crossing approximation. Eventhough the Kondo temperature is smaller than excitation energy to the CEFtriplet, the Kondo effect appears at temperatures higher than the CEFsplitting, and accordingly only quasi-elastic peak is found in the magneticspectra. On the other hand, at lower temperatures the CEF splitting suppressesthe Kondo effect and inelastic peak develops. The broad quasi-elastic neutronscattering spectra observed in PrFe_4P_{12} at temperatures higher than thequadrupole order correspond to the parameter range where the CEF splittings areunimportant.