Orbital degeneracy as a source of frustration in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">LiNiO</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Vernay, F.; Penc, Karlo; Fazekas, P.; Mila, Frédéric

doi:10.1103/physrevb.70.014428

Cited by 93 publications

(107 citation statements)

References 28 publications

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“…Pati et al have shown that this dimerized phase extends to a very large portion of the phase diagram around this point. From that point of view, the identification of dimer phases in the context of spin-orbital models of BaVS 3 [29] and of LiNiO 2 [24] is not unexpected, and the tendency to dimerize can be considered to be a generic trend of spin-orbital models. What seems to be more specific to these spin-orbital models of LiNiO 2 and BaVS 3 is the quasi-degeneracy of all nearest-neighbour dimer coverings.…”

Section: Discussionmentioning

confidence: 99%

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The emergence of resonating valence bond physics in spin–orbital models

Mila

Vernay

Ralko

et al. 2007

J. Phys.: Condens. Matter

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Abstract. We discuss how orbital degeneracy, which is usually removed by a cooperative Jahn-Teller distortion, could under appropriate circumstances lead rather to a Resonating Valence Bond spin-orbital liquid. The key points are: i) The tendency to form spin-orbital dimers, a tendency already identified in several cases; ii) The mapping onto Quantum Dimer Models, which have been shown to possess Resonating Valence Bond phases on the triangular lattice. How this program can be implemented is explained in some details starting from a microscopic model of LiNiO 2 .

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Section: Discussionmentioning

confidence: 99%

“…A fairly general description of this system is given by a Kugel-Khomskii Hamiltonian defined in terms of Wannier functions centered on the Ni sites by two hopping integrals t h and t ′ h , the on-site Coulomb repulsion U and the Hund's coupling J which, on a given bond, takes the form [24] …”

Section: Microscopic Modelmentioning

confidence: 99%

The emergence of resonating valence bond physics in spin–orbital models

Mila

Vernay

Ralko

et al. 2007

J. Phys.: Condens. Matter

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“…The lack of obvious orbital ordering in LiNiO 2 and the orbital degeneracy which would arise in its absence has motivated many theoretical authors to consider coupled orbital and spin degrees of freedom 7,8,9,18,19,20,21 as a mechanism to suppress magnetic ordering at low temperatures. Other recent work suggests orbital and spin degrees of freedom are decoupled 14 .…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Ordering and spin waves inNaNiO2: A stacked quantum ferromagnet

et al. 2005

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Neutron scattering measurements on powder NaNiO2 reveal magnetic Bragg peaks and spin waves characteristic of strongly correlated s=1/2 magnetic moments arranged in ferromagnetic layers which are stacked antiferromagnetically. This structure lends itself to stacking sequence frustration in the presence of mixing between nickel and alkali metal sites, possibly providing a natural explanation for the enigmatic spin glass state of the isostructural compound, LiNiO2 .

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“…5 In spite of this, LiNiO 2 still remains interesting because of the absence of a cooperative Jahn-Teller distortion that is expected for such a system with orbital degeneracy. 6 Experimental results on LiNiO 2 are rather controversial. It always suffers from nonstoichiometry: excess Ni ions replace Li ions, which gives rise to a local interlayer FM coupling that competes with an intrinsic AFM coupling.…”

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confidence: 99%

Spin-12triangular lattice with orbital degeneracy in a metallic oxideAg2Ni

et al. 2006

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A novel metallic and magnetic transition metal oxide Ag 2 NiO 2 is studied by means of resistivity, magnetic susceptibility, specific heat and X-ray diffraction. The crystal structure is characterized by alternating stacking of a Ni 3+ O 2 layer and a (Ag 2 ) + layer, the former realizing a spin-1/2 triangular lattice with e g orbital degeneracy and the latter providing itinerant electrons. It is found that the NiO 2 layer exhibits orbital ordering at T s = 260 K and antiferromagnetic spin ordering at T N = 56 K. Moreover, a moderately large mass enhancement is found for the itinerant electrons, suggesting a significant contribution from the nearly localized Ni 3d state to the Ag 5s state that forms a broad band. PACS number: 75.50-y, 75.30.Et, 72.80.GaFrustration on triangle-based lattices is one of key ingredients for quantum phenomena to be induced in various electron systems with spin, orbital and charge degrees of freedom. It suppresses classical long-range order (LRO) associated with these degrees of freedom and sometimes leads to a "liquid" ground state with finite entropy. 1 Another interesting issue emerging recently is to clarify the role of frustration on itinerant electrons in frustrated lattices. One would expect some influence especially for a strongly correlated electron system, where both charge and spin degrees of freedom may coexist marginally. A good example is found in a mixed valent vanadium spinel compound LiV 2 O 4 that exhibits unusual heavy-Fermion like behavior. 2, 3 It is suggested that orbital degeneracy survives due to frustration on the pyrochlore lattice and gives rise to a large mass enhancement of 3d electrons.LiNiO 2 was first assumed to be a candidate for the spin-1/2 triangular antiferromagnet, because it comprises Ni 3+ ions in the low-spin state (t 2g 6 e g 1 ) with an isotropic S = 1/2, arranged in a triangular lattice which stacks alternatingly with a nonmagnetic Li + layer. 4 However, later studies have revealed that a net magnetic interaction between neighboring Ni 3+ spins in LiNiO 2 is ferromagnetic (FM), not antiferromegnetic (AFM), and thus there is no frustration for spins. 5 In spite of this, LiNiO 2 still remains interesting because of the absence of a cooperative Jahn-Teller distortion that is expected for such a system with orbital degeneracy. 6 Experimental results on LiNiO 2 are rather controversial. It always suffers from nonstoichiometry: excess Ni ions replace Li ions, which gives rise to a local interlayer FM coupling that competes with an intrinsic AFM coupling. 5, 7 It is believed that ideal LiNiO 2 would be a quantum spin-orbital liquid without LRO, where frustration prevents orbital ordering as well as spin ordering in spite of dominant FM couplings. 8It is pointed out, alternatively, that the absence of LRO is due to the excess Ni ions and that ideal LiNiO 2 would be

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Orbital degeneracy as a source of frustration inLiNiO2

Cited by 93 publications

References 28 publications

The emergence of resonating valence bond physics in spin–orbital models

The emergence of resonating valence bond physics in spin–orbital models

Ordering and spin waves inNaNiO2: A stacked quantum ferromagnet

Spin-12triangular lattice with orbital degeneracy in a metallic oxideAg2Ni

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