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Ning, Fanlong; Imai, Takashi; Statt, B. W.; Chou, F. C.

doi:10.1103/physrevlett.93.237201

Cited by 59 publications

(74 citation statements)

References 28 publications

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“…units) One of the remarkable features of 1/T 1 T is a rather significant decrease found for x≤0.6 with decreasing T. 34) It reminds us of the pseudo gap phenomenon well known in underdoped Cu oxide high-T c superconductors. 35,36) For x~0.75, it is nearly T independent in the T region above 100K and then increases with decreasing T below 100K.…”

Section: Nmr/nqr Studiesmentioning

confidence: 99%

Magnetic Correlation of Na_xCoO₂and Successive Phase Transitions of Na_0.5CoO₂–NMR and Neutron Diffraction Studies–

et al. 2005

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Section: Nmr/nqr Studiesmentioning

confidence: 99%

Magnetic Correlation of Na_xCoO₂and Successive Phase Transitions of Na_0.5CoO₂–NMR and Neutron Diffraction Studies–

et al. 2005

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“…[9,10,11,12,13,14,15,16,17,18] The Co ions are enclosed in edge sharing O-octahedra which in turn are separated by insulating Na layers. [19,20] The latter mainly act as a charge reservoir.…”

Section: Introductionmentioning

confidence: 99%

Localized versus itinerant magnetic moments inNa0.7CoO2

et al. 2006

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Based on experimental 59 Co-NMR data in the temperature range between 0.1 and 300 K, we address the problem of the character of the Co 3d-electron based magnetism in Na0.7CoO2. Temperature dependent 59 Co-NMR spectra reveal different Co environments below 300 K and their differentiation increases with decreasing temperature. We show that the 23 Na-and 59 Co-NMR data may consistently be interpreted by assuming that below room temperature the Co 3d-electrons are itinerant. Their magnetic interaction appears to favor an antiferromagnetic coupling, and we identify a substantial orbital contribution χ orb to the d−electron susceptibility. At low temperatures χ orb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T −1 1 (T ) confirms significant variations in the dynamics of this electronic subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1 K but this scenario still leaves a number of open questions.

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“…25 However, the authors noted that the degree of charge disproportionation is rather small. More recent 59 Co and 23 Na NMR measurements find no signature of differences in the charge state of the cobalt ions at the two distinct sites 26 suggesting that all the Co atoms are in the charge state Co ͑3.5Ϯ ͒+ , where Ͻ 0.2 gives an upper bound on the extent of charge ordering.…”

Section: Charge Order On the Cobalt Ionsmentioning

confidence: 99%

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5
Powell
¹
,
Merino
²
,
McKenzie
³

2009
Phys. Rev. B
9
0
2
0
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We present a strongly correlated mean-field theory of the ionic Hubbard model on the triangular lattice with alternating stripes of site energy using Barnes-Coleman slave bosons. We study the paramagnetic phases of this theory at three quarters filling, where it is a model of Na 0.5 CoO 2 , Rb 0.5 CoO 2 , and K 0.5 CoO 2 . This theory has two bands of fermionic quasiparticles: one of which is filled or nearly filled and hence weakly correlated; the other is half-filled or nearly half-filled and hence strongly correlated. Further results depend strongly on the sign of the hopping integral t. The light band is always filled for t Ͼ 0, but only becomes filled for ͉⌬ / t͉ Ն 1.5 for t Ͻ 0, where ⌬ is the difference in the site energies of the two sublattices. A metal-charge transfer insulator transition occurs at ͉⌬ / t͉ = 5.0 for t Ͼ 0 and ͉⌬ / t͉ = 8.0 for t Ͻ 0. In the charge transfer insulator complete charge disproportionation occurs: one sublattice is filled and the other is half-filled. We compare our results with exact diagonalization calculations and experiments on Na 0.5 CoO 2 and discuss the relevance of our results to Rb 0.5 CoO 2 and K 0.5 CoO 2 . We propose a resolution of seemingly contradictory experimental results on Na 0.5 CoO 2 . Many experiments suggest that there is a charge gap, yet quantum oscillations are observed suggesting the existence of quasiparticle states at arbitrarily low excitation energies. We argue that the heavy band is gapped while the light band, which contains less than one charge carrier per 100 unit cells, remains ungapped.

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Spin Dynamics in the Carrier-DopedS=12Triangular Lattice ofNaxC

Cited by 59 publications

References 28 publications

Magnetic Correlation of Na_xCoO₂and Successive Phase Transitions of Na_0.5CoO₂–NMR and Neutron Diffraction Studies–

Magnetic Correlation of Na_xCoO₂and Successive Phase Transitions of Na_0.5CoO₂–NMR and Neutron Diffraction Studies–

Localized versus itinerant magnetic moments inNa0.7CoO2

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5
Powell
¹
,
Merino
²
,
McKenzie
³

2009
Phys. Rev. B
9
0
2
0
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Spin Dynamics in the Carrier-DopedS=12Triangular Lattice ofNaxC

Cited by 59 publications

References 28 publications

Magnetic Correlation of NaxCoO2and Successive Phase Transitions of Na0.5CoO2–NMR and Neutron Diffraction Studies–

Magnetic Correlation of NaxCoO2and Successive Phase Transitions of Na0.5CoO2–NMR and Neutron Diffraction Studies–

Localized versus itinerant magnetic moments inNa0.7CoO2

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5Powell1, Merino2, McKenzie3 2009Phys. Rev. B9020View full textAdd to dashboardCite

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Magnetic Correlation of Na_xCoO₂and Successive Phase Transitions of Na_0.5CoO₂–NMR and Neutron Diffraction Studies–

Magnetic Correlation of Na_xCoO₂and Successive Phase Transitions of Na_0.5CoO₂–NMR and Neutron Diffraction Studies–

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5
Powell
¹
,
Merino
²
,
McKenzie
³

2009
Phys. Rev. B
9
0
2
0
View full text Add to dashboard Cite