Anomalous heavy-fermion and ordered states in the filled skutterudite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">PrFe</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">P</mml:mi></mml:mrow><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Aoki, Yuji; Namiki, Takahiro; Matsuda, Tatsuma D.; Abé, Keisuke; Sugawara, Hitoshi; Sato, Hideyuki

doi:10.1103/physrevb.65.064446

Cited by 183 publications

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“…At 5 T, the magnitude of the magnetization of both PrFe 4 P 12 and PrOs 4 As 12 below their transition temperatures is much less than the Pr 3ϩ free-ion value of 3.2 B ͞Pr ion; however, there is a clear step-like feature in the M(H) data for PrFe 4 P 12 , indicating a metamagnetic transition (19), whereas features in the M(H) data for PrOs 4 As 12 are much more subtle. In high fields, the C(T)͞T data for both systems display a broad dome-shaped anomaly at low temperatures, but in zero field there is no indication of a second-phase transition in the C(T)͞T data for PrFe 4 P 12 (6). Because neutron diffraction measurements of PrFe 4 P 12 in zero field did not find any indication of long-range magnetic order and measurements in an applied field have revealed the presence of an induced AFM moment, antiferroquadrupolar ordering is speculated as being the source of the observed behavior of PrFe 4 P 12 below 6.5 K (7,22).…”

Section: Discussionmentioning

confidence: 97%

“…For H Ն 3 T, a broad maximum was observed in C e (T), reminiscent of that observed in C e (T) for PrFe 4 P 12 (6). Therefore, the C e (T) data for PrOs 4 As 12 were analyzed in terms of the resonance-level model (RLM) of Schotte and Schotte (12) used in ref.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, the C e (T) data for PrOs 4 As 12 were analyzed in terms of the resonance-level model (RLM) of Schotte and Schotte (12) used in ref. 6 for PrFe 4 P 12 . This model has three parameters: the width of a Lorentzian peak in the density of states ⌬ Ϸ k B T K (where T K is the Kondo temperature), the spin S, and a Zeeman term gH associated with the applied field, although it was also necessary to scale the curves by a factor f. The parameters S, ⌬, and f were held fixed for all fields, while the term gH was varied.…”

Section: Discussionmentioning

confidence: 99%

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Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs₄As₁₂

Maple

Butch

Frederick

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Electrical resistivity, specific heat, and magnetization measurements to temperatures as low as 80 mK and magnetic fields up to 16 T were made on the filled skutterudite compound PrOs4As12. The measurements reveal the presence of two ordered phases at temperatures below approximately 2.3 K and in fields below approximately 3 T. Neutron-scattering experiments in zero field establish an antiferromagnetic ground state <2.28 K. In the antiferromagnetically ordered state, the electronic-specific heat coefficient ␥ Ϸ 1 J͞mol⅐K 2 below 1.6 K and 0 < H < 1.25 T. The temperature and magnetic-field dependence of the electrical resistivity and specific heat in the paramagnetic state are consistent with single-ion Kondo behavior with a low Kondo temperature on the order of 1 K. The electronic-specific heat in the paramagnetic state can be described by the resonance-level model with a large zero-temperature electronic-specific heat coefficient that decreases with increasing magnetic field from approximately 1 J͞mol⅐K 2 at 3 T to approximately 0.2 J͞mol⅐K 2 at 16 T.heavy fermion ͉ Kondo effect ͉ antiferromagnetism T he compound PrOs 4 As 12 belongs to the family of filled skutterudites, which have the formula AT 4 X 12 , where A ϭ alkali metal, alkaline earth, lanthanide, or actinide, T ϭ Fe, Os, or Ir, and X ϭ P, As, or Sb. Because the ions reside in an atomic cage with a large number of X nearest neighbors, the hybridization between the lanthanide filler ion localized 4f states and the conduction-electron states is appreciable, often resulting in strongly correlated electron phenomena. In a recent article (1), we reported a study of the physical properties of single crystals of the filled skutterudite compound PrOs 4 As 12 between approximately 0.4 and 300 K by means of magnetization M, specific heat C, and electrical resistivity measurements. The previous study revealed that the compound exhibits two (possibly three) ordered phases below approximately 2.5 K in zero field and approximately 3 T at zero temperature from kinks in M as a function of magnetic field H and temperature T. Features in the (T) and C(T) data in zero field can be identified with transitions into the two ordered phases below 2.5 K. The magnetic susceptibility conforms to a Curie-Weiss law below approximately 20 K with an effective magnetic moment eff ϭ 2.77 B ͞formula unit consistent with a ⌫ 5 ground state in a cubic crystalline electric field and a cusp at approximately 2.5 K, indicative of antiferromagnetic (AFM) order. These results provide another example of the wide range of correlated electron ground states that are found in the Pr-based filled skutterudites, which include conventional (Bardeen, Cooper, Schrieffer) superconductivity (e.g., PrRu 4 Sb 12 ) (2), unconventional superconductivity (e.g., PrOs 4 Sb 12 ) (3, 4), heavy fermion behavior (e.g., PrFe 4 P 12 , PrOs 4 Sb 12 ) (5-8), antiferroquadrupolar order (e.g., PrFe 4 P 12 , PrOs 4 Sb 12 ), and magnetic order (e.g., PrFe 4 Sb 12 ) (9, 10). In this article, we report measurements of the te...

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs₄As₁₂

Maple

Butch

Frederick

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…15 Nevertheless, for most of the reported samples the conductivity due to thermally activated carriers predominates above T ≈ 200 K. Thus, for the semiconductor CeFe 4 P 12 with gap of ≃ 0.15 eV and estimated Debye temperature of Θ D ≃ 500 K, 16 at least a weak coupling of the R-X stretching mode and the c-e should be expected. This compound experiences a huge increase in the density of thermally activated conduction-carriers at T ≈ 150 K.…”

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confidence: 99%

Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1−xGd
Garcia
¹
,
Venegas
²
,
Pagliuso
³

et al. 2011
Phys. Rev. B

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We report electron spin resonance (ESR) measurements in the Gd 3+ doped semiconducting filled skutterudite compound Ce1−xGdxFe4P12 (x ≈ 0.001). As the temperature, T , varies from T ≃ 150 K to T ≃ 165 K the Gd 3+ ESR fine and hyperfine structures coalesce into a broad inhomogeneous single resonance. At T ≃ 200 K the line narrows and as T increases further the resonance becomes homogeneous with a thermal broadening of 1.1(2) Oe/K. These results suggest that the origin of these features may be associated to a subtle interdependence of thermally activated mechanisms that combine: i) an increase with T of the density of activated conduction-carriers across the Tdependent semiconducting pseudogap; ii) the Gd 3+ Korringa relaxation process due to an exchange interaction, J f d S.s, between the Gd 3+ localized magnetic moments and the thermally activated conduction-carriers and; iii) a relatively weak confining potential of the rare-earth ions inside the oversized (Fe2P3)4 cage, which allows the rare-earths to become rattler Einstein oscillators above T ≈ 148 K. We argue that the rattling of the Gd 3+ ions, via a motional narrowing mechanism, also contributes to the coalescence of the ESR fine and hyperfine structure.

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“…Tx,71.27.+a,75.10.Dg,78.70.Nx Praseodymium filled skutterudite compounds, with general formula PrT 4 M 12 , where T is one of the transition metals Fe, Ru, or Os, and M is a pnictogen (P, As, or Sb), show a remarkable variety of interesting physical phenomena, including metal-insulator transitions [1], quadrupolar heavy fermion behavior [2,3], and superconductivity [4]. In particular, PrOs 4 Sb 12 has attracted attention as a heavy fermion superconductor, in which quadrupolar fluctuations may play an important role in the pairing mechanism [5].…”

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confidence: 99%

Crystal Field Potential ofPrOs4Sb12: Consequences for Superconductivity

et al. 2004

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The results of inelastic neutron scattering provide a solution for the crystal field level scheme in PrOs4Sb12, in which the ground state in the cubic crystal field potential of T h symmetry is a Γ1 singlet. The conduction electron mass enhancement is consistent with inelastic exchange scattering, and we propose that inelastic quadrupolar, or aspherical Coulomb, scattering is responsible for enhancing the superconducting transition temperature. PrOs4Sb12 appears to be the first compound in which aspherical Coulomb scattering is strong enough to overcome magnetic pair-breaking and increase Tc.PACS numbers: 74.70. Tx,71.27.+a,75.10.Dg,78.70.Nx Praseodymium filled skutterudite compounds, with general formula PrT 4 M 12 , where T is one of the transition metals Fe, Ru, or Os, and M is a pnictogen (P, As, or Sb), show a remarkable variety of interesting physical phenomena, including metal-insulator transitions [1], quadrupolar heavy fermion behavior [2,3], and superconductivity [4]. In particular, PrOs 4 Sb 12 has attracted attention as a heavy fermion superconductor, in which quadrupolar fluctuations may play an important role in the pairing mechanism [5]. This proposal is based on two key observations; (i) there is a significant f-electroninduced mass enhancement of the conduction electrons, observed in specific heat, upper critical field [5,6], and de Haas-van Alphen measurements [7], and (ii) the magnetic susceptibility indicates that the crystal field ground state is non-magnetic [5].A knowledge of the crystal field ground state is essential to understanding the role of the f-electrons in the superconductivity. In analyzing the magnetic susceptibility and specific heat, Bauer et al considered two possible crystal field models [5]. In cubic symmetry, the Pr 3+ ion splits into a singlet (Γ 1 ), a non-magnetic doublet (Γ 3 ), and two magnetic triplets (Γ 4 and Γ 5 ). Crystal field models with either the Γ 1 singlet or Γ 3 doublet as ground state were both broadly consistent with the data; in both cases, the Γ 5 triplet was the lowest excited level estimated to be at less than 1 meV in energy. A Γ 3 non-Kramers doublet ground state is of particular interest as it provides the necessary conditions for quadrupolar Kondo fluctuations to be responsible for the heavy fermion behavior [8], and was favored by analyses of the entropy [9,10]. However, the alternative Γ 1 singlet ground state has also been proposed following experiments that have explored the crossover to a field-induced ordered phase [11,12,13], so this important question remains unresolved.Inelastic neutron scattering is the most direct method of determining the crystal field potential and level scheme of metallic rare earth systems. In this report, we present the results of a comprehensive set of measurements of crystal field transitions in PrOs 4 Sb 12 as a function of temperature. From a simultaneous profile refinement of all the spectra, normalized on an absolute intensity scale, we have concluded that the Γ 1 singlet is the ground state level. Discr...

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Anomalous heavy-fermion and ordered states in the filled skutteruditePrFe4P12

Cited by 183 publications

References 30 publications

Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs₄As₁₂

Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs₄As₁₂

Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1−xGd
Garcia
¹
,
Venegas
²
,
Pagliuso
³

et al. 2011
Phys. Rev. B

Crystal Field Potential ofPrOs4Sb12: Consequences for Superconductivity

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Anomalous heavy-fermion and ordered states in the filled skutteruditePrFe4P12

Cited by 183 publications

References 30 publications

Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs4As12

Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs4As12

Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1−xGdGarcia1, Venegas2, Pagliuso3 et al. 2011Phys. Rev. B

Crystal Field Potential ofPrOs4Sb12: Consequences for Superconductivity

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Product

Resources

About

Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs₄As₁₂

Field-dependent ordered phases and Kondo phenomena in the filled skutterudite compound PrOs₄As₁₂

Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1−xGd
Garcia
¹
,
Venegas
²
,
Pagliuso
³

et al. 2011
Phys. Rev. B