Dynamics of singlet triplet crystalline electric field levels in Pr skutterudites

Dynamics of 4f ² electrons with the singlet-triplet crystalline electric field (CEF) levels in Pr skutterudites is studied by taking account of hybridization with conduction electrons. Dynamical properties are numerically derived with use of the non-crossing approximation (NCA). The effective exchange interaction depends much on the nature of the CEF triplet wave functions. Although the CEF singlet is eventually formed at low temperatures, Kondo effect is seen at temperatures higher than the CEF splitting. The crossover from the Kondo-like behavior to the CEF singlet-like one is explicitly shown in the electrical resistivity and magnetic intensity.