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Shamoto, S.; Sato, M.; Tranquada, J. M.; Sternlieb, B. J.; Shirane, G.

doi:10.1103/physrevb.48.13817

Cited by 186 publications

(151 citation statements)

References 49 publications

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“…Such a distinctively dominant magnetic energy scale immediately suggests that it is a key player in the mechanisms of the HTSC. The close relationship between the magnetism and the HTSC is supported by a body of INS studies, in particular by discoveries of the sharp resonance peak of magnetic excitations and the low-energy incommensurate scattering, the temperature, doping − y 2 ) orbital typically used for magnetic form factor calculations 6,13,28,29 . d,e, The equal-level surfaces of the magnetic form factor squared at |F(Q)| 2 = 0.13 ≈ 1/e 2 for the wavefunctions in a and b, respectively.…”

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confidence: 93%

“…25) and using the anisotropic magnetic form factor of the Cu 2+ ion, following the procedure adopted in previous studies 6,13,28,29 . Only two parameters are varied in such fitting: the in-chain exchange coupling J , which determines the overall energy scale of magnetic excitations, and the prefactor A, which accounts for the possible statistical and systematic errors of our intensity measurements and ideally should be equal to one.…”

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confidence: 99%

“…Surprisingly, previous neutron diffraction studies reported very little, if any covalent reduction of the ordered magnetic moment in cuprates [28][29][30] . This controversy was pointed out by Kaplan et al 30 , but the point was declared moot in view of the probably fortuitous agreement between the experiment and the semiclassical theory.…”

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Effect of covalent bonding on magnetism and the missing neutron intensity in copper oxide compounds

et al. 2009

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Theories involving highly energetic spin fluctuations are among the leading contenders for explaining high-temperature superconductivity in the cuprates 1 . These theories could be tested by inelastic neutron scattering (INS), as a change in the magnetic scattering intensity that marks the entry into the superconducting state provides a precise quantitative measure of the spin-interaction energy involved in the superconductivity 2-11 . However, the absolute intensities of spin fluctuations measured in neutron scattering experiments vary widely, and are usually much smaller than expected from fundamental sum rules, resulting in 'missing' INS intensity 2-5,12,13 . Here, we solve this problem by studying magnetic excitations in the one-dimensional related compound, Sr 2 CuO 3 , for which an exact theory of the dynamical spin response has recently been developed. In this case, the missing INS intensity can be unambiguously identified and associated with the strongly covalent nature of magnetic orbitals. We find that whereas the energies of spin excitations in Sr 2 CuO 3 are well described by the nearestneighbour spin-1/2 Heisenberg Hamiltonian, the corresponding magnetic INS intensities are modified markedly by the strong 2p-3d hybridization of Cu and O states. Hence, the ionic picture of magnetism, where spins reside on the atomic-like 3d orbitals of Cu 2+ ions, fails markedly in the cuprates.Over the past 20 years, the magnetic properties of cuprates have been studied extensively by theorists and experimentalists alike. These systems are usually described within the antiferromagnetic Mott insulator model, in which the unpaired electrons are localized on the Cu 2+ ions because of the overwhelming cost in the on-site Coulomb interaction energy, U , associated with the charge transfer between the Cu sites, a strong correlation phenomenon. Virtual electron hopping, which in the one-band Hubbard model of a Mott insulator often adopted for cuprates 14 is quantified by the transition matrix element, t , results in antiferromagnetic exchange. For t U , electronic spins form the only low-energy electronic degrees of freedom. Their properties are well approximated by the spin-1/2 Heisenberg Hamiltonian on the lattice 15 , H = J i(nn)j S i S j , with the nearest-neighbour exchange coupling J ≈ 4t 2 /U . This description conveniently splits the problem of electronic magnetism in the Mott insulator into two parts 15 . The first deals with the electron transfer between the neighbouring sites of the crystal lattice, which is determined by the overlap integral (∼t ) of the wavefunctions occupied by the unpaired electrons, and leads to the Hubbard model, or the Heisenberg spin Hamiltonian. The second concerns the form of the electronic Wannier wavefunctions, that is, the shape of the spin magnetization cloud associated with 1 ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK, 2 Department of Physics, University College London, Gower Street, London WC1E 6BT, UK, 3 London Centre for Nanotechnology, 17-19 Go...

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Effect of covalent bonding on magnetism and the missing neutron intensity in copper oxide compounds

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“…This is the position that magnetism is found in the parent compound, YBa 2 Cu 3 O 6.15 , which is an insulator with a Néel transition temperature well above room temperature and has been studied previously. 10,11 The defining attribute of the DDW state is that the moment should be largely along the c-axis. Small moments in the sample crystal originating from the parent compound should be located in the a-b plane as is found for this material.…”

Section: Introductionmentioning

confidence: 99%

Polarized neutron measurement of magnetic order inYBa2Cu3O6.45

et al. 2004

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Orbital current order of the d-density-wave type (DDW) has been postulated to explain the pseudogap in the high temperature superconductors. We have performed neutron scattering experiments to search for this order and show here the results obtained on an YBa 2 Cu 3 O 6.45 sample using the best neutron spectrometers available. We argue that the data are consistent with a small, largely c-axis-directed moment, found below about 200K.PACS numbers: 72.15. Gd, 61.12.Ld, 71.30.+h 2 The microscopic origin of the pseudogap is one of the most puzzling attributes of the cuprate superconductors. A review of the various experimental techniques used to determine the pseudogap is given by Timusk and Statt. 1 It is generally considered to stem from pairing above the superconducting transition temperature T C 2,3 or result from another ground-state differentiated from superconductivity by a quantum critical point. 4,5 Chakravarty et al. 6 but a competing phase judged to stem from impurities made the identification of the DDW state difficult. The moments from the bond currents result in peaks at the (h/2, k/2, l) superlattice positions of the reciprocal lattice. This is the position that magnetism is found in the parent compound, YBa 2 Cu 3 O 6.15 , which is an insulator with a Néel transition temperature well above room temperature and has been studied previously. 10,11 The defining attribute of the DDW state is that the moment should be largely along the c-axis. Small moments in the sample crystal originating from the parent compound should be located in the a-b plane as is found for this material. Other magnetic impurity phases could be possible, but to our knowledge no such phases 3 are known to have high temperature (above 50K) magnetic order along the c-axis for the YBa 2 Cu 3 O 6+x system.In order to determine the direction of the moments for the antiferromagnetic state it is necessary to use polarized neutrons, as outlined by Moon et al. in 1969. 12 The crystal used in the experiments is twinned so that a* could not be differentiated from b*. We thus consider the crystal to be tetragonal so that the (1, 1, 0) reflection showed no peak indicating that the higher order scattering from the monochromator was well removed. Figure 1b shows the result of a HF SF measurement through the (1/2, 1/2, 1) position at 20 K. The scan range on the high Q side of the scan is limited by intense NSF scattering that is difficult to correct for with the rather small flipping ratio as seen in Fig 3a. Nevertheless, a peak is observed at (0.5, 0.5, 1) and a Gaussian fit results in a height of 11±2 counts with a width of 0.01±0.002 FWHM at the position 0.5±0.001 r.l.u. The peak is resolution limited, giving a correlation length of about 380Å. Figure 1c shows no evidence for a peak at a temperature of 150K. Multiple runs were averaged to obtain the observed error bars. 5These scans took over two days each and are difficult to improve in a reasonable time period.Also, since the magnetic signal is so small, a higher flipping ratio is des...

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“…For x = 0.075 at 200 K and x = 0 at 5 K, the data for 0 ≤ L ≤ 4 are plotted. Note that the plotted integrated intensities are normalized by the magnetic form factor for the d x 2 −y 2 orbital [12]; thus, the results for the different L values can be directly compared. The results show that the intensities at different L values agree within the measurement uncertainty as shown by error bars.…”

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confidence: 99%

Neutron Scattering Study of Spin Fluctuations in La₂₋_xSr_xCuO₄ by Four-Dimensional Mapping of Neutron Cross-Sections Using the 4SEASONS Chopper Spectrometer

Wakimoto¹,

Ikeuchi²,

Arai³

et al. 2015

Proceedings of the 2nd International Symposium on Science at J-Parc — Unlocking the Mysteries of Life, Matter and the Universe

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Spin fluctuation spectra and phonon neutron cross-sections of La 2 CuO 4 and La 2−x Sr x CuO 4 with x = 0.075 and 0.30 were studied by four-dimensional mapping of neutron cross-sections using the 4SEASONS chopper spectrometer installed at the Material and Life Science Facility, J-PARC. The purpose of this study is to verify the relation between the maximum at the energy transfer of 15 meV in dynamical spin susceptibility and the superconductivity. We observed identical maxima in spin fluctuation spectra at 15 meV at several L positions in the data of the superconducting x = 0.075 sample measured at 5 K. In addition, we confirmed that the maximum disappears in the 200 K data of the x = 0.075 composition and in the 5 K data of the undoped La 2 CuO 4 . These results imply that the 15 meV maximum is a unique feature of the superconducting concentrations at low temperatures.

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Neutron-scattering study of antiferromagnetism inYBa2Cu3

Cited by 186 publications

References 49 publications

Effect of covalent bonding on magnetism and the missing neutron intensity in copper oxide compounds

Effect of covalent bonding on magnetism and the missing neutron intensity in copper oxide compounds

Polarized neutron measurement of magnetic order inYBa2Cu3O6.45

Neutron Scattering Study of Spin Fluctuations in La₂₋_xSr_xCuO₄ by Four-Dimensional Mapping of Neutron Cross-Sections Using the 4SEASONS Chopper Spectrometer

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Neutron-scattering study of antiferromagnetism inYBa2Cu3

Cited by 186 publications

References 49 publications

Effect of covalent bonding on magnetism and the missing neutron intensity in copper oxide compounds

Effect of covalent bonding on magnetism and the missing neutron intensity in copper oxide compounds

Polarized neutron measurement of magnetic order inYBa2Cu3O6.45

Neutron Scattering Study of Spin Fluctuations in La2−xSrxCuO4 by Four-Dimensional Mapping of Neutron Cross-Sections Using the 4SEASONS Chopper Spectrometer

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Neutron Scattering Study of Spin Fluctuations in La₂₋_xSr_xCuO₄ by Four-Dimensional Mapping of Neutron Cross-Sections Using the 4SEASONS Chopper Spectrometer