Structure analysis of mutually incommensurate composite crystal (Ca0.5Y0.5)0.80CuO2

Gotoh, Yoshito; Yamaguchi, Iwao; Takeya, Satoshi; Fujihisa, Hiroshi; Honda, Kazumasa; Ito, T.; Oka, Kunihiko; Yamaguchi, Hiroshi

doi:10.1016/j.jallcom.2004.12.114

Cited by 2 publications

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“…Due to lacking space a critical discussion of the O vacancy scenario and the related Cu 4p hole bonding scenario by Shu et al instead of the correlated Cu 3d covalent electron picture must be considered elsewhere. We mention here only that the main reason for disorder in Ca 2 Y 2 Cu 5 O 10 is likely not the presence of O vacancies, as stated by Shu et al, but the intrinsic misfit with the Ca 2+ Y 3+ -chains that surround and distort the CuO 2 chains [34][35][36]. Based on this complex structure there are no hints pointing to O vacancies.…”

Section: Introductionmentioning

confidence: 67%

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO₂ chains of Li₂CuO₂’

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In a recent work devoted to the magnetism of Li 2 CuO 2 , Shu et al (2017 New J. Phys. 19, 023026) have proposed a 'simplified' unfrustrated microscopic model that differs considerably from the models refined through decades of prior work. We show that the proposed model is at odds with known experimental data, including the reported magnetic susceptibility χ(T) data up to 550K. Using an 8th order high-temperature expansion for χ(T), we show that the experimental data for Li 2 CuO 2 are consistent with the prior model derived from inelastic neutron scattering studies. We also establish the T-range of validity for a Curie-Weiss law for the real frustrated magnetic system. We argue that the knowledge of the long-range ordered magnetic structure for T<T N and of χ(T) in a restricted Trange provides insufficient information to extract all of the relevant couplings in frustrated magnets; the saturation field and INS data must also be used to determine several exchange couplings, including the weak but decisive frustrating antiferromagnetic interchain couplings.Li 2 CuO 2 takes a special place among the still increasing family of frustrated chain compounds with edge-sharing CuO 4 plaquettes and a ferromagnetic (FM) nearest neighbor (NN) inchain coupling J 1 [1]. This unique position is due to its ideal planar CuO 2 chain structure and its well-defined ordering characterized by a 3D Neél-type arrangement of adjacent chains whose magnetic moments are aligned ferromagnetically along the chains (b-axis). Li 2 CuO 2 is well studied in both experiment and theory (see e.g. [2][3][4][5][6][7][8][9][10][11]) and serves nowadays as a reference system for more complex and structurally less ideal systems. In particular, it is accepted in the quantum magnetism community that the leading FM coupling is the NN inchain coupling J 1 . (J 1 is also dominant but antiferromagnetic (AFM) in the special spin-Peierls case of CuGeO 3 [12].) There is always also a finite frustrating AFM next-nearest neighbor (NNN) coupling J 2 >0, see figure 1, left. This inchain frustration is quantified by J J 2 1 a = | |. In the present case, and in that of the related Ca 2 Y 2 Cu 5 O 10 , there are only frustrating OPEN ACCESS RECEIVED

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Section: Introductionmentioning

confidence: 67%

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO₂ chains of Li₂CuO₂’

et al. 2018

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Highly dispersive magnons with spin-gap-like features in the frustrated ferromagneticS=12chain compoundCa2Y2Cu
Matsuda
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Ma
²
,
Garlea
³

et al. 2019
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We report inelastic neutron scattering experiments in Ca2Y2Cu5O10 and map out the full one magnon dispersion which extends up to a record value of 53 meV for frustrated ferromagnetic (FM) edge-sharing CuO2 chain (FFESC) cuprates. A homogeneous spin-1/2 chain model with a FM nearest-neighbor (NN), an antiferromagnetic (AFM) next-nearest-neighbor (NNN) inchain, and two diagonal AFM interchain couplings (ICs) analyzed within linear spin-wave theory (LSWT) reproduces well the observed strong dispersion along the chains and a weak one perpendicularly. The ratio α = |Ja2/Ja1| of the FM NN and the AFM NNN couplings is found as ∼0.23, close to the critical point αc = 1/4 which separates ferromagnetically and antiferromagnetically correlated spiral magnetic ground states in single chains, whereas αc > 0.25 for coupled chains is considerably upshifted even for relatively weak IC. Although the measured dispersion can be described by homogeneous LSWT, the scattering intensity appears to be considerably reduced at ∼11.5 and ∼28 meV. The gap-like feature at 11.5 meV is attributed to magnon-phonon coupling whereas based on density matrix renormalization group simulations of the dynamical structure factor the gap at 28 meV is considered to stem partly from quantum effects due to the AFM IC. Another contribution to that gap is ascribed to the intrinsic superstructure from the distorting incommensurate pattern of CaY cationic chains adjacent to the CuO2 ones. It gives rise to non-equivalent CuO4 units and Cu-O-Cu bond angles Φ and a resulting distribution of all exchange integrals. The J's fitted by homogeneous LSWT are regarded as average values. The record value of the FM NN integral J1 = 24 meV among FFESC cuprates can be explained by a non-universal Φ( = 90 • ) and Cu-O bond length dependent anisotropic mean direct FM Cu-O exchangeK pd ∼120 meV, similar to a value of 105 meV for Li2CuO2, in accord with larger values for La2CuO4 and CuGeO3 (∼110 meV) reported by Braden et al. [Phys. Rev. B 54, 1105] phenomenologically. Enhanced K pd values are also needed to compensate a significant AFM J dd ≥ 6 meV from the dd channel, generic for FFESC cuprates but ignored so far.

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Structure analysis of mutually incommensurate composite crystal (Ca0.5Y0.5)0.80CuO2

Cited by 2 publications

References 16 publications

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO₂ chains of Li₂CuO₂’

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO₂ chains of Li₂CuO₂’

Highly dispersive magnons with spin-gap-like features in the frustrated ferromagneticS=12chain compoundCa2Y2Cu
Matsuda
¹
,
Ma
²
,
Garlea
³

et al. 2019
Phys. Rev. B
Self Cite
11
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0
0
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Structure analysis of mutually incommensurate composite crystal (Ca0.5Y0.5)0.80CuO2

Cited by 2 publications

References 16 publications

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO2 chains of Li2CuO2’

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO2 chains of Li2CuO2’

Highly dispersive magnons with spin-gap-like features in the frustrated ferromagneticS=12chain compoundCa2Y2CuMatsuda1, Ma2, Garlea3 et al. 2019Phys. Rev. BSelf Cite11000View full textAdd to dashboardCite

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Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO₂ chains of Li₂CuO₂’

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO₂ chains of Li₂CuO₂’

Highly dispersive magnons with spin-gap-like features in the frustrated ferromagneticS=12chain compoundCa2Y2Cu
Matsuda
¹
,
Ma
²
,
Garlea
³

et al. 2019
Phys. Rev. B
Self Cite
11
0
0
0
View full text Add to dashboard Cite