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Cao, D.; Bridges, F.; Bushart, S.; Bauer, E. D.; Maple, M. B.

doi:10.1103/physrevb.67.180511

Cited by 31 publications

(14 citation statements)

References 15 publications

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“…Indications of static off-center movement have been indeed found in metastable skutterudites filled with heavy rare earths. 32,33 However, no indications of a lock-in-type phase transition were found for NaFe 4 Sb 12 . At room temperature, off-center displacements of the sodium atom can be ruled out due to the spherical distribution of the difference electron density 34 in the vicinity of the Na position (Fig.…”

Section: A Crystal Structurementioning

confidence: 99%

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12and
Leithe‐Jasper
¹
,
Schnelle
²
,
Rösner
³

et al. 2004
Phys. Rev. B
89
2
77
0
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The synthesis, chemical, structural, and magnetic properties of alkali-metal compounds with filledskutterudite structure, NaFe 4 Sb 12 and KFe 4 Sb 12 , are described. X-ray and neutron diffraction and elemental analysis established the crystal structure without defects and disorder on the cation site. The temperature and pressure dependence of the cubic unit cell of NaFe 4 Sb 12 and the displacement parameter of Na are investigated. The electronic structure is calculated by density functional methods (LMTO, FPLO). Quantum chemical calculations (electron localization function) reveal the covalent character of both Fe-Sb and Sb-Sb interactions. Electronic structure calculations within the local density approximation exhibit a band ferromagnetic ground state and predict a half-metallic behavior. In contrast to isostructural alkaline-earth compounds (CaFe 4 Sb 12 and BaFe 4 Sb 12 ), the alkali-metal skutterudites are itinerant electron ferromagnets with small magnetic moments (Ϸ0.25 B / Fe atom) and T C Ϸ 85 K. Yet the paramagnetic moments of all four compounds are between 1.5 B and 1.7 B per Fe atom, indicating similar Stoner factors. Temperature-dependent 57 Fe and 121 Sb Mössbauer spectroscopies confirm the ferromagnetic state in the sodium compound with very small hyperfine fields at the iron and antimony sites.

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Section: A Crystal Structurementioning

confidence: 99%

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12and
Leithe‐Jasper
¹
,
Schnelle
²
,
Rösner
³

et al. 2004
Phys. Rev. B
89
2
77
0
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“…Quite recently a small off-center displacement of Pr ion in PrOs 4 Sb 12 has been observed by x-ray absorption measurements. 18 The rattling motion in the clathrate compound PrOs 4 Sb 12 with the heavy-fermion superconductivity has not been clarified yet.…”

mentioning

confidence: 99%

Quadrupolar effect and rattling motion in the heavy-fermion superconductorPrOs4Sb12

et al. 2004

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The elastic properties of a filled skutterudite PrOs 4 Sb 12 with a heavy fermion superconductivity at T C ϭ1.85 K have been investigated. The elastic softening of (C 11 ϪC 12 )/2 and C 44 with lowering temperature down to T C indicates that the quadrupolar fluctuation due to the CEF state plays a role for the Cooper paring in superconducting phase of PrOs 4 Sb 12 . A Debye-type dispersion in the elastic constants around 30 K revealed a thermally activated ⌫ 23 rattling due to the off-center Pr-atom motion obeying ϭ 0 exp(E/k B T) with an attempt time 0 ϭ8.8ϫ10 Ϫ11 s and an activation energy Eϭ168 K. It is remarkable that the charge fluctuation of the off-center motion with ⌫ 23 symmetry may mix with the quadrupolar fluctuation and enhance the elastic softening of (C 11 ϪC 12 )/2 just above T C .The rare-earth cubic compounds based on Pr 3ϩ ions have received much attention because various unusual properties are expected at low temperatures. The system with a non-ϪJ y 2 favors a quadrupole ordering. We refer the ⌫ 3 ground state systems as a metallic compound PrPb 3 showing the antiferro-quadrupole ordering at T Q ϭ0.4 K 1 and a semiconductor PrPtBi undergoing ferroquadrupole ordering at T Q ϭ1.2 K. 2 PrSb is known as a singlet ground state system. 3 The elastic constant (C 11 ϪC 12 )/2 is responsible for the quadrupolar susceptibility of O 2 0 and O 2 2 with ⌫ 3 symmetry, while C 44 is for the susceptibility of O yz ϭJ y J z ϩJ z J y , O zx ϭJ z J x ϩJ x J z , O xy ϭJ x J y ϩJ y J x with ⌫ 5 symmetry. The softening of (C 11 ϪC 12 )/2 and C 44 is useful proof to clarify the quadrupolar effects of Pr-based compounds.Recently, Bauer et al. have found a new-type of the heavy-fermion superconductor in a filled skutterudite PrOs 4 Sb 12 with space group T h 5 (Im3). 4 The heavy fermion state with a large specific heat coefficient ␥ϭ750 mJ/mol K 2 of PrOs 4 Sb 12 exhibits the superconducting transition at T C ϭ1.85 K associated with a large jump ⌬C/T C ϳ500 mJ/mol K 2 . A sign of the double transition in the specific heat has been found. 5 The thermal transport measurement in fields suggests the two distinct superconducting phases in PrOs 4 Sb 12 . 6 The nuclear spin relaxation rate 1/T 1 of Sb indicates unconventional superconductivity possessing neither a coherence peak nor a T 3 -power law. 7 The muon spin relaxation in PrOs 4 Sb 12 yields a penetration depth indicating a new type of energy gap. 8 The odd-parity Cooper pairing mediated by the quadrupole fluctuation is argued as unconventional heavy-fermion superconductivity in PrOs 4 Sb 12 . 9 Because the magnetic susceptibility is rather silent to distinguish non-magnetic ⌫ 23 doublet from ⌫ 1 singlet, it has not been settled whether the CEF ground state of PrOs 4 Sb 12 is ⌫ 23 doublet or ⌫ 1 singlet. 4,10 The measurement of (C 11 ϪC 12 )/2 and C 44 responsible for the quadrupolar sus-ceptibility in PrOs 4 Sb 12 is a central issue to clarify the CEF state and the interplay of the quadrupolar fluctuation to the superconductivity in PrOs 4 Sb 12 .

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“…The discovery of superconductivity in the heavy fermion compound PrOs 4 Sb 12 1,2 has spawned a flurry of experimental 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19 and theoretical 9,20,21,22,23,24,25 activity. PrOs 4 Sb 12 is the first Prbased heavy fermion superconductor and the first among the family of rare-earth filled skutterudite compounds.…”

Section: Introductionmentioning

confidence: 99%

Superconducting states in the tetrahedral compoundPrOs4Sb12

2004

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We find possible superconducting states for tetrahedral (T h ) symmetry crystals with strong spinorbit coupling using Landau theory. Additional symmetry breaking within the superconducting state is considered. We discuss nodes of the gap functions for the different states, secondary superconducting order parameters and coupling to the elastic strain. By comparing our results to experiments, we find that superconductivity in PrOs4Sb12 is best described by the three-dimensional representations of point group T h .

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X-ray-absorption spectroscopy study of the heavy-fermion superconductorPrOs4Sb12

Cited by 31 publications

References 15 publications

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12and
Leithe‐Jasper
¹
,
Schnelle
²
,
Rösner
³

et al. 2004
Phys. Rev. B
89
2
77
0
View full text Add to dashboard Cite

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12and
Leithe‐Jasper
¹
,
Schnelle
²
,
Rösner
³

et al. 2004
Phys. Rev. B
89
2
77
0
View full text Add to dashboard Cite

Quadrupolar effect and rattling motion in the heavy-fermion superconductorPrOs4Sb12

Superconducting states in the tetrahedral compoundPrOs4Sb12

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X-ray-absorption spectroscopy study of the heavy-fermion superconductorPrOs4Sb12

Cited by 31 publications

References 15 publications

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12andLeithe‐Jasper1, Schnelle2, Rösner3 et al. 2004Phys. Rev. B892770View full textAdd to dashboardCite

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12andLeithe‐Jasper1, Schnelle2, Rösner3 et al. 2004Phys. Rev. B892770View full textAdd to dashboardCite

Quadrupolar effect and rattling motion in the heavy-fermion superconductorPrOs4Sb12

Superconducting states in the tetrahedral compoundPrOs4Sb12

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Product

Resources

About

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12and
Leithe‐Jasper
¹
,
Schnelle
²
,
Rösner
³

et al. 2004
Phys. Rev. B
89
2
77
0
View full text Add to dashboard Cite

Weak itinerant ferromagnetism and electronic and crystal structures of alkali-metal iron antimonides: NaFe4Sb12and
Leithe‐Jasper
¹
,
Schnelle
²
,
Rösner
³

et al. 2004
Phys. Rev. B
89
2
77
0
View full text Add to dashboard Cite