Hybridization effects and multipole orders in Pr skutterudites

Abstract

Theoretical account is given of 4f-electron dynamics and multipole orders in Pr skutterudites with particular attention to (i) mechanism of the crystalline electric field (CEF) splitting leading to a pseudo-quartet ground state;(ii) Kondo effect due to exchange interactions involving the pseudo-quartet;(iii) multipole orders in the lattice of the pseudo-quartet in magnetic field.Competition between the point-charge interaction andhybridization between 4f and conduction electrons is identified as the key for controlling the CEF splitting. It is found that one of two pseudo-spins forming the pseudo-quartet has a ferromagnetic exchange, while the other has an antiferromagnetic exchange with conduction electrons. The Kondo effect is clearly seen in the resistivity calculated by the NCA, provided the low-lying triplet above the singlet is mainly composed of the ${\Gamma }_4$-type wave functions.If the weight of the ${\Gamma }_5$-type is large in the triplet, the Kondo effect does not appear.This difference caused by the nature of the triplet explains the presence of the Kondo effect inPrFe${}_4$P${}_{12}$, and its absence in PrOs${}_4$Sb${}_{12}$.By taking the minimal model with antiferro-quadrupole (AFQ) and ferro-type intersite interactions for dipoles and octupoles between nearest-neighbors,the mean-field theory reproduces the overall feature of the multiple ordered phases in PrFe${}_4$P${}_{12}$. The AFQ order with the ${\Gamma }_3$-type symmetry is found to be stable only as a mixture of $O_2^0$ and $O_2^2$ components.

21 pages, to be published in proc. YKIS2004

Cited by in corpus (5)

• Skutterudite Results Shed Light on Heavy Fermion Physics
• Microscopic Mechanism for Staggered Scalar Order in PrFe4P12
• Hybridization and multipole orders of 4f electrons in Pr skutterudites
• Microscopic Aspects of Multipole Properties of Filled Skutterudites
• Diffraction from Ordered States of Higher Multipoles