Hybridization and multipole orders of 4f electrons in Pr skutterudites

Abstract

Characteristics of hybridization and multipole orders of $4f$-electrons in Pr skutterudites are explained in terms of a pseudo-quartet composed of crystalline electric field (CEF) singlet and the triplet. It is shown that the contrasting behaviors observed in PrFe${}_4$P${}_{12}$ and PrOs${}_4$Sb${}_{12}$ are ascribed to the difference in triplet wave functions and the CEF splittings.Since a macroscopic degeneracy remains even in the ordered phase with the ${\Gamma }_3$-type antiferro-quadrupole (AFQ) order,a model with strong AFQ fluctuation and static monopole/hexadecapole order is proposed for PrFe${}_4$P${}_{12}$.The remaining cubic symmetry explains qualitatively the behavior of staggered magnetization observed by NMR and neutron scattering. For identification of possible hexadecapole orders in PrFe${}_4$P${}_{12}$ andPrRu${}_4$P${}_{12}$, eightfold intensity pattern is predicted in the azimuthal angle scan of resonant X-ray scattering. In PrOs${}_4$Sb${}_{12}$, the ferromagnetic exchange coupling with the conduction band does not lead to magnetic Kondo effect, but a momentum-dependent quadrupole coupling can give rise to enhanced effective mass, which should be sensitive to disorder.

Invited paper to be published in Proc. Int. Symp. on Advances in the Physics and Chemistry of Actinide Compounds (Suppl. J. Phys. Soc. Jpn)

References in corpus (10)

• Thermodynamical Study on the Heavy-Fermion Superconductor PrOs4Sb12: Evidence for Field-Induced Phase Transition
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Cited by in corpus (2)

• Determining the crystal-field ground state in rare earth Heavy Fermion materials using soft-x-ray absorption spectroscopy
• Microscopic Aspects of Multipole Properties of Filled Skutterudites