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Zaliznyak, Igor; Woo, Hyun-Joo; Perring, T. G.; Broholm, C.; Frost, Christopher; Takagi, H.

doi:10.1103/physrevlett.93.087202

Cited by 106 publications

(133 citation statements)

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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: 99%

“…In fact, such analysis was typically carried out using the ionic Cu 2+ magnetic form factor, which totally neglects the covalency effects. A number of studies 5,6,13 have consequently found significant deviations of the INS spectral weight from sum rules, which in particular state that the integral of S(Q,E), over Q and energy should equal NS(S + 1), where N is the number of magnetic sites in the sample and S is the spin at each site (S = 1/2 for cuprates). Whereas covalency is a leading suspect for these outstanding discrepancies, their unambiguous association with the covalent magnetic form factor in planar cuprates is hindered by the absence of a precise theory describing the dynamical behaviour of the 2D spin system.…”

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confidence: 99%

“…The corresponding extraordinary strength of Cu-O covalent bonding is responsible for the recordhigh antiferromagnetic exchange couplings found in cuprates, J ≈ 1,500 K (refs 5, 6) in the two-dimensional (2D) La 2 CuO 4 and J ≈ 2,600 K (ref. 13) in its 1D chain relative SrCuO 2 . Such a distinctively dominant magnetic energy scale immediately suggests that it is a key player in the mechanisms of the HTSC.…”

mentioning

confidence: 99%

“…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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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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confidence: 99%

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

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“…Recent ab initio cluster calculations [99,100] have been able to achieve reasonable agreement with experiment. While the magnitude of J in layered cuprates is rather large, it is not extreme; a value of J = 226(12) meV has been measured for Cu-O chains in SrCuO 2 [101].…”

Section: Spin Wavesmentioning

confidence: 99%

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

Tranquada

Handbook of High-Temperature Superconductivity

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Summary. Neutron scattering studies have provided important information about the momentum and energy dependence of magnetic excitations in cuprate superconductors. Of particular interest are the recent indications of a universal magnetic excitation spectrum in hole-doped cuprates. That starting point provides motivation for reviewing the antiferromagnetic state of the parent insulators, and the destruction of the ordered state by hole doping. The nature of spin correlations in stripeordered phases is discussed, followed by a description of the doping and temperature dependence of magnetic correlations in superconducting cuprates. After describing the impact on the magnetic correlations of perturbations such as an applied magnetic field or impurity substitution, a brief summary of work on electron-doped cuprates is given. The chapter concludes with a summary of experimental trends and a discussion of theoretical perspectives. IntroductionNeutron scattering has played a major role in characterizing the nature and strength of antiferromagnetic interactions and correlations in the cuprates. Following Anderson's observation [1] that La 2 CuO 4 , the parent compound of the first high-temperature superconductor, should be a correlated insulator, with moments of neighboring Cu 2+ ions anti-aligned due to the superexchange interaction, antiferromagnetic order was discovered in a neutron diffraction study of a polycrystalline sample [2]. When single-crystal samples became available, inelastic studies of the spin waves determined the strength of the superexchange, J, as well as weaker interactions, such as the coupling between CuO 2 layers. The existence of strong antiferromagnetic spin correlations above the Néel temperature, T N , has been demonstrated and explained. Over time, the quality of such characterizations has improved considerably with gradual evolution in the size and quality of samples and in experimental techniques.Of course, what we are really interested in understanding are the optimallydoped cuprate superconductors. It took much longer to get a clear picture of the magnetic excitations in these compounds, which should not be surprising

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Spin Structures and Spin Wave Excitations

Zaliznyak

2007

Handbook of Magnetism and Advanced Magnetic Materials

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Electronic spin interactions and the resulting spin structures which give rise to various kinds of magnetism existing in many‐electron condensed matter systems are discussed. In most cases, spin structure and excitations in a spin system can be understood in the framework of semiclassical spin‐wave theory. Basic examples observed in magnetic neutron diffraction and inelastic magnetic neutron scattering experiments are presented and discussed with reference to such description. Relationship between the structure of the crystal lattice and spin arrangement and energy dispersion of spin excitations in the crystal are discussed and illustrated by some recent experimental results.

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Spinons in the Strongly Correlated Copper Oxide Chains inSrCuO2

Cited by 106 publications

References 28 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

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

Spin Structures and Spin Wave Excitations

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