Elastic Anomalies of Polycrystalline SmRu<sub>4</sub>P<sub>12</sub>Associated with Metal–Insulator Transition

Yoshizawa, Michito; Nakanishi, Y.; Kumagai, T.; Oikawa, Masafumi; Sekine, Chihiro; Shirotani, Ichimin

doi:10.1143/jpsj.73.315

Cited by 40 publications

(28 citation statements)

References 12 publications

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“…As shown in Fig. 4(b), the ground state is Γ 67 quartet for x>0, consistent with the experimental results of elastic constant 38 and magnetic entropy 39 for SmRu 4 P 12 . For n=6, the total angular momentum J becomes zero, since S=L=3 in this case.…”

Section: Cef Schemes For Filled Skutteruditessupporting

confidence: 89%

Microscopic Approach to Magnetism and Superconductivity of f-Electron Systems with Filled Skutterudite Structure

Hotta

2005

J. Phys. Soc. Jpn.

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In order to gain a deep insight into f -electron properties of filled skutterudite compounds from a microscopic viewpoint, we investigate the multiorbital Anderson model including Coulomb interactions, spinorbit coupling, and crystalline electric field effect. First we examine the local f -electron state in detail in comparison with the results of LS and j-j coupling schemes. For each case of n=1∼13, where n is the number of f electrons per rare-earth ion, the model is analyzed by using the numerical renormalization group (NRG) method to evaluate magnetic susceptibility and entropy of f electron. In particular, for the f 2 -electron system corresponding to the Pr-based filled skutterudite, it is found that magnetic fluctuations significantly remain at low temperatures, even when the ground state is Γ1 singlet, if Γ (2) 4 triplet is the excited state with small excitation energy. In order to make further step to construct a simplified model which can be treated even in a periodic system, we also analyze the Anderson model constructed based on the j-j coupling scheme by using the NRG method. It is clearly observed that the magnetic properties are quite similar to those of the original Anderson model. Then, we construct an orbital degenerate Hubbard model based on the j-j coupling scheme to investigate the mechanism of superconductivity of filled skutterudites. In the 2-site model, we carefully evaluate the superconducting pair susceptibility for the case of n=2 and find that the susceptibility for off-site Cooper pair is clearly enhanced only in a transition region in which the singlet and triplet ground states are interchanged. We envision a scenario that unconventional superconductivity induced by magnetic fluctuations may occur in the f 2 -electron system with Γ1 ground state such as Pr-based filled skutterudite compounds.

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Section: Cef Schemes For Filled Skutteruditessupporting

confidence: 89%

Microscopic Approach to Magnetism and Superconductivity of f-Electron Systems with Filled Skutterudite Structure

Hotta

2005

J. Phys. Soc. Jpn.

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“…This issue will be discussed later in terms of Grüneisen parameter Ω. Unfortunately, we can not detect an anomaly at T N under pressure, as was successfully done in magnetic fields [9]. …”

Section: Resultsmentioning

confidence: 69%

“…The only experimentally accessible ultrasound modes for a polycrystalline sample, i. e., longitudinal C L propagating parallel to polarization and transverse C T propagating perpendicular to polarization, were measured as a function of temperature under different hydrostatic pressures. The absolute values of C L , C T and bulk modulus C B of SmRu 4 P 12 at 100 K are 153, 24.6 and 120 GPa, respectively [9].…”

Section: Methodsmentioning

confidence: 94%

“…Specific heat measurements suggest a crystalline electric field (CEF) scheme consisting of a Γ 67 ground state quartet and an excited doublet Γ 5 at about 60 K in the T h symmetry [4,8]. This scheme is plausible for understanding other measurements including the elastic * Electronic address: yoshizawa@iwate-u.ac.jp constant [9,10]. Noticeably, the Γ 67 quartet with both orbital and magnetic degeneracy, is a key point for understanding the various properties of SmRu 4 P 12 .…”

Section: Introductionmentioning

confidence: 94%

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Anomalous elastic softening ofSmRu4P12under high pressure

et al. 2007

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The filled skutterudite compound SmRu4P12 undergoes a complex evolution from a paramagnetic metal (phase I) to a probable multipolar ordering insulator (phase II) at TMI ∼ 16.5 K, then to a magnetically ordered phase (phase III) at TN ∼ 14 K. Elastic properties under hydrostatic pressures were investigated to study the nature of the ordering phases. We found that distinct elastic softening above TMI is induced by pressure, giving evidence of quadrupole degeneracy of the ground state in the crystalline electric field. It also suggests that quadrupole moment may be one of the order parameters below TMI under pressure. Strangely, the largest degree of softening is found in the transverse elastic constant CT at around 0.5-0.6 GPa, presumably having relevancy to the competing and very different Grüneisen parameters Ω of TMI and TN. Interplay between the two phase transitions is also verified by the rapid increase of TMI under pressure with a considerably large Ω of 9. Our results can be understood on the basis of the proposed octupole scenario for SmRu4P12.

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“…[2][3][4][5][6][7] Most likely the nesting condition of the Fermi surface with the wave vector Q ¼ ð1; 0; 0Þ drives the MI transition. The MI transition is accompanied by a multipole order, called phase II, whose nature is not clear so far.…”

Section: Introductionmentioning

confidence: 99%

Ordering and Crossover in a Pseudo-Sextet Localized Electron Model –Possible Scenario for SmRu₄P₁₂Skutterudite–

Kiss

Kuramoto

2009

J. Phys. Soc. Jpn.

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A crystalline electric field (CEF) model of localized 4f 5 electrons is proposed for understanding intriguing ordering phenomena in SmRu 4 P 12 . We take the CEF quartet and doublet (pseudo-sextet) of the Hund's rule ground state with J ¼ 5=2, and include intersite interactions between multipoles by the mean-field theory. The model leads to a multipole order with representation À 5u , and shows the following features: (i) increasing transition temperature T MI with increasing magnetic field; (ii) an anomaly in specific heat and other thermodynamic quantities at lower temperature T ? , (iii) sharpening of the anomaly at T ? as the magnetic field increases. These behaviors reproduce salient features observed experimentally in SmRu 4 P 12 . Possible mechanisms for spontaneous magnetic moment are discussed.

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Elastic Anomalies of Polycrystalline SmRu₄P₁₂Associated with Metal–Insulator Transition

Cited by 40 publications

References 12 publications

Microscopic Approach to Magnetism and Superconductivity of f-Electron Systems with Filled Skutterudite Structure

Microscopic Approach to Magnetism and Superconductivity of f-Electron Systems with Filled Skutterudite Structure

Anomalous elastic softening ofSmRu4P12under high pressure

Ordering and Crossover in a Pseudo-Sextet Localized Electron Model –Possible Scenario for SmRu₄P₁₂Skutterudite–

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Elastic Anomalies of Polycrystalline SmRu4P12Associated with Metal–Insulator Transition

Cited by 40 publications

References 12 publications

Microscopic Approach to Magnetism and Superconductivity of f-Electron Systems with Filled Skutterudite Structure

Microscopic Approach to Magnetism and Superconductivity of f-Electron Systems with Filled Skutterudite Structure

Anomalous elastic softening ofSmRu4P12under high pressure

Ordering and Crossover in a Pseudo-Sextet Localized Electron Model –Possible Scenario for SmRu4P12Skutterudite–

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Product

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Elastic Anomalies of Polycrystalline SmRu₄P₁₂Associated with Metal–Insulator Transition

Ordering and Crossover in a Pseudo-Sextet Localized Electron Model –Possible Scenario for SmRu₄P₁₂Skutterudite–