Ordering and Crossover in a Pseudo-Sextet Localized Electron Model —Possible Scenario for SmRu4P12 Skutterudite—

概要

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A crystalline electric field (CEF) model of localized 4f5 electrons is proposed for understanding intriguing ordering phenomena in SmRu4P12. We take the CEF quartet and doublet (pseudo-sextet) of the Hund’s rule ground state with $J=5/2$, and include intersite interactions between multipoles by the mean-field theory. The model leads to a multipole order with representation $\Gamma_{5u}$, and shows the following features: (i) increasing transition temperature $T_{\text{MI}}$ with increasing magnetic field; (ii) an anomaly in specific heat and other thermodynamic quantities at lower temperature $T^{\star}$, (iii) sharpening of the anomaly at $T^{\star}$ as the magnetic field increases. These behaviors reproduce salient features observed experimentally in SmRu4P12. Possible mechanisms for spontaneous magnetic moment are discussed.
2009-12-15