ELECTRON DIFFRACTION STUDY OF La2Li0.5Cu0.5O4

Moshopoulou, E.; Thompson, J. D.; Fisk, Z.; Sarrao, J. L.

doi:10.1016/s0022-3697(98)00220-0

Cited by 5 publications

(4 citation statements)

References 7 publications

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“…Ce 2 RhIn 8 is a member of the linear homologous series of heavy fermion materials Ce m T n In 3m + 2n , where m = 1, 2; n = 0, 1; T = Co, Rh, Ir. These materials adopt tetragonal crystal structures built by monolayers (for m = 1) or bilayers (for m = 2) of face-sharing cuboctahedra [CeIn 3 ], and monolayers (for n = 1) of edge-sharing rectangular parallelepipeds [TIn 2 ] stacked alternatively in the [001] direction (Grin et al, 1979;Moshopoulou et al, 2001;Moshopoulou, Prokes et al, 2002;Macaluso et al, 2003). The series has attracted considerable interest over the last five years, not only because of the interesting low-temperature properties of its members but also because it allows investigation of the role of spatial dimensionality in controlling the heavy-fermion state and the cooperative phenomena of unconventional superconductivity and magnetism.…”

Section: Introductionmentioning

confidence: 99%

Structure of Ce₂RhIn₈: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Moshopoulou¹,

Ibberson²,

Sarrao³

et al. 2006

Acta Crystallogr B Struct Sci

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The room-temperature crystal structure of the heavy fermion antiferromagnet Ce2RhIn8, dicerium rhodium octaindide, has been studied by a combination of high-resolution synchrotron X-ray reciprocal-space mapping of single crystals and high-resolution time-of-flight neutron powder diffraction. The structure is disordered, exhibiting a complex interplay of non-periodic, partially correlated planar defects, coexistence and segregation of polytypic phases (induced by periodic planar ;defects'), mosaicity (i.e. domain misalignment) and non-uniform strain. These effects evolve as a function of temperature in a complicated way, but they remain down to low temperatures. The room-temperature diffraction data are best represented by a complex mixture of two polytypic phases, which are affected by non-periodic, partially correlated planar defects, differ slightly in their tetragonal structures, and exhibit different mosaicities and strain values. Therefore, Ce2RhIn8 approaches the paracrystalline state, rather than the classic crystalline state and thus several of the concepts of conventional single-crystal crystallography are inapplicable. The structural results are discussed in the context of the role of disorder in the heavy-fermion state and in the interplay between superconductivity and magnetism.

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Section: Introductionmentioning

confidence: 99%

Structure of Ce₂RhIn₈: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Moshopoulou¹,

Ibberson²,

Sarrao³

et al. 2006

Acta Crystallogr B Struct Sci

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“…A unique opportunity to study isolated Cu 3+ centers and non-ZR IUC order parameters without the confounding contributions of the nearest neighbor antiferromagnetically correlated CuO 4 clusters is provided in La 2 Li x Cu 1−x O 4 at x = 0.5 49 . At this composition the Li and Cu ions form an ideally ordered superlattice 50,51 in which all Cu 3+ ions are surrounded by four in-plane Li ions (1s 2 , closed shell electronic configuration) and thus create weakly coupled, almost isolated CuO 4 clusters.…”

Section: B Some Experimental Manifestation Of Novel Iuc Order Parametersmentioning

confidence: 99%

Local Intra-Unit-Cell Order Parameters in Cuprates Beyond Zhang-Rice Model

Moskvin

2016

J Supercond Nov Magn

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Starting with a minimal model with the on-site Hilbert space reduced to only three effective valence centers CuO 7−,6−,5− 4 (nominally Cu 1+,2+,3+ ) we present an unified approach to the description of the variety of the local intra-unit-cell (IUC) order parameters determining a low-energy physics in cuprates. Central point of the model implies the occurrence of unconventional on-site quantum superpositions of the three valent states characterized by different hole occupation: n h =0,1,2 for Cu 1+,2+,3+ centers, respectively, different conventional spin: s=1/2 for Cu 2+ center and s=0 for Cu 1+,3+ centers, and different orbital symmetry:B1g for the ground states of the Cu 2+ center and A1g for the Cu 1+,3+ centers, respectively. The latter does result in a spontaneous orbital symmetry breaking accompanying the formation of the on-site mixed valence superpositions with emergence of the IUC orbital nematic order parameter of the B1g = B1g × A1g (∝ dx2−y2) symmetry. To describe the diagonal and off-diagonal, or quantum local charge order we develop an S=1 pseudospin model with a non-Heisenberg effective Hamiltonian that provides a physically clear description of "the myriad of phases" from a bare parent antiferromagnetic insulating phase to a Fermi liquid in overdoped cuprates. Conventional spin density ρs for mixed valence superpositions can vary inbetween 0 and 1 in accordance with the weight of the Cu 2+ center in the superposition. We show that the superconductivity and spin magnetism are nonsymbiotic phenomena with competing order parameters. Furthermore we argue that instead of a well-isolated Zhang-Rice (ZR) singlet 1 A1g the ground state of the hole Cu 3+ center in cuprates should be described by a complex 1 A1g-1,3 B2g-1,3 Eu multiplet, formed by a competition of conventional hybrid Cu 3d-O 2p b1g(σ) ∝ d x 2 −y 2 state and purely oxygen nonbonding O 2pπ states with a2g(π) and eux,y(π) symmetry. In contrast with inactive ZR singlet we arrive at several novel competing IUC orbital and spin-orbital order parameters, e.g., electric dipole and quadrupole moments, Ising-like net orbital magnetic moment, orbital toroidal moment, intra-plaquette's staggered order of Ising-like oxygen orbital magnetic moments. As a most impressive validation of the non-ZR model we explain fascinating results of recent neutron scattering measurements that revealed novel type of the IUC magnetic ordering in pseudogap phase of several hole-doped cuprates.

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“…9 In 1988 Zhang and Rice 10 proposed that the doped and initial holes in a "hole" CuO 4 5− center, a cluster analog of the Cu 3+ ion, form a "well isolated" spin and orbital 1 A 1g singlet ͑a ZR singlet͒ in which both holes occupy states with the same b 1g -symmetry and are formed by hybridization of 3d x 2 −y 2-orbitals of Cu and O 2p-orbitals of all four oxygen ions. 11 In this compound the Li ͑Li + ͒ and Cu ions form an ideally ordered superlattice with a chessboard ordering 12,13 where all the Cu ions are surrounded by four diamagnetic Li ions with a filled 1s 2 -configuration, which forms at square lattice that isolates the hole CuO 4 5− centers, i.e., cluster analogs of Cu 3+ ions, spatially. Since the early 1990's the Zhang-Rice model has become the basis for describing the physics of low energies for the cuprates, in particular, different variants of the Hubbard model simply do not take the nonbonding O 2p-orbitals into account.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of hole centers in CuO2 planes of cuprates

Moskvin¹,

Panov²

2011

Low Temperature Physics

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A theoretical analysis and a large amount of experimental data indicate that the structure of the valence hole states in doped cuprates is more complicated than assumed in the simple Zhang-Rice singlet model. In fact, we are dealing with a competition between a hybrid Cu3d–O2pb1g∝dx2−y2-state and purely oxygen nonbonding states with a2g- and eux,y∝px,y-symmetries. Thus, as a cluster analog of a Cu3+ ion, the ground state of a non-Zhang-Rice CuO45− hole center of this sort should be described by complicated A1g1−B2g1,3−Eu1,3 multiplet with a set of charge, orbital, and spin order parameters, some of which are well known (e.g., spin moment or “ferromagnetic” Ising orbital momentum localized on oxygen ions) while others are unconventional or hidden (e.g., “antiferromagnetic” ordering of Ising orbital momenta localized on four oxygen atoms or a combined spin-orbital-quadrupole ordering). The non-Zhang-Rice CuO45− centers are actually singlet-triplet pseudo-Jahn-Teller centers with strong vibron coupling to the lattice. The complicated structure of the ground-state multiplet of the hole centers shows up in many of the unusual properties of doped cuprates, in particular, their pseudo-gap phase.

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ELECTRON DIFFRACTION STUDY OF La2Li0.5Cu0.5O4

Cited by 5 publications

References 7 publications

Structure of Ce₂RhIn₈: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Structure of Ce₂RhIn₈: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Local Intra-Unit-Cell Order Parameters in Cuprates Beyond Zhang-Rice Model

Electronic structure of hole centers in CuO2 planes of cuprates

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ELECTRON DIFFRACTION STUDY OF La2Li0.5Cu0.5O4

Cited by 5 publications

References 7 publications

Structure of Ce2RhIn8: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Structure of Ce2RhIn8: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Local Intra-Unit-Cell Order Parameters in Cuprates Beyond Zhang-Rice Model

Electronic structure of hole centers in CuO2 planes of cuprates

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Structure of Ce₂RhIn₈: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials

Structure of Ce₂RhIn₈: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials