Multipolar Interaction Derived from d–f Hybridization in Pr-Based Filled Skutterudite Compounds

Abstract

The conduction bands of the skutterudite compounds are composed of p orbitals of the pnictogen cages and d orbitals of the transition metal ions. In this paper, we address the effect of hybridization between the d bands and localized 4 f states in relation with ordering and fluctuation of multipole moments in Pr-based filled skutterudites. First, we study the properties of a non-degenerate d band around the zone center in the framework of a tight-binding band model. Introducing a realistic form of the d – f hybridization, we show that the a g band can be hybridized only with the Γ 8 orbitals of f electrons. Then, we derive d – f multipolar interactions from the hybridization in the localized limit of f electrons in which the basis states are restricted to the singlet–triplet crystal field states. It is found that the quadrupolar interaction of the O x y -type becomes predominant in the case of the singlet ground state, whereas the triplet ground state apparently favors the magnetic interaction. The relati...