The structure of La2CuO4 and LaSrVO4

Longo, J.M.; Raccah, P. M.

doi:10.1016/s0022-4596(73)80010-6

Cited by 449 publications

(100 citation statements)

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“…In particular, the recently developed difference dedicated configuration interaction (DDCI) technique [16] has proven to be capable of accurately predicting the value of J in a large family of wide gap ionic insulators [17] [14,18]. To construct the models, experimental geometries [3,5,6,[19][20][21][22] are used. This constitutes the only input data external to theory.…”

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confidence: 99%

Accurate Prediction of Large Antiferromagnetic Interactions in High-TcHgBa2Ca<

2000

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The in-plane nearest-neighbor Heisenberg magnetic coupling constant, J, of La 2 CuO 4 , Nd 2 CuO 4 , Sr 2 CuO 2 Cl 2 , YBa 2 Cu 3 O 6 , and undoped HgBa 2 Ca n21 Cu n O 2n121d (n 1, 2, 3) is calculated from accurate ab initio configuration interaction calculations. For the first four compounds, the theoretical J values are in quantitative agreement with experiment. For the Hg-based compounds the predicted values are 2135 meV (n 1) and ϳ2160 meV (n 2, 3), the latter being much larger than in previous cases and, for n 3, increasing with pressure. Nevertheless, the physics governing J in all these layered cuprates appears to be the same. Moreover, calculations suggest a possible relationship between J and T c . PACS numbers: 74.25.Jb, 74.25.Ha, 75.30.Et More than ten years have passed since the discovery of the high-T c superconductivity in several cuprate compounds and, up to now, there has been no agreement on a complete theory capable of explaining their anomalous physical properties [1]. The layered crystal structure, the strong antiferromagnetic coupling between neighbor Cu 21 ions in these layers, and the strongly correlated nature of their electronic structure have been pointed out to play a very important role in the fundamental mechanisms of superconductivity [1,2]. The high-T c superconductors are produced by moderate doping of "parent compounds" such as La 2 CuO 4 , Nd 2 CuO 4 , or YBa 2 Cu 3 O 6 . It is widely accepted that proximity to the insulating phase and the interaction of dopant carriers with magnetic degrees of freedom are fundamental aspects for the existence of high-T c superconductivity. Recent theories strongly suggest that magnetic coupling is at the very origin of the superconducting state [2]. Thus, the magnetic coupling constants defining the magnetic structure of these compounds are key magnitudes in establishing trends and theories based on model Hamiltonians.Recently, several families of layered cuprates, containing Bi, Tl, or Hg, have been synthesized. The HgBa 2 Ca n21 Cu n O 2n121d (n 1, 2, 3) family [3][4][5] includes HgBa 2 Ca 2 Cu 3 O 81d , the compound with the highest transition temperature observed to date (133 K at ambient pressure and 164 K under 31 GPa) [4,6,7]. The difficult synthesis and the layered structure of those materials limits the capability of obtaining pure crystals large enough to perform accurate measurements of their magnetic properties. This restricts the theoretical understanding due to the difficulty to obtain reliable estimates of the model Hamiltonian parameters. Modern theoretical approaches to electronic structure could provide accurate values of these parameters, such as the nearest-neighbor Heisenberg magnetic coupling constant J, thus providing a more detailed description of these materials.Unfortunately, because of the strong correlated nature of the electronic structure and the antiferromagnetic insulating character of these cuprates, band structure calculations based on the local density approximation (LDA) or on the generalized gradient app...

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confidence: 99%

Accurate Prediction of Large Antiferromagnetic Interactions in High-TcHgBa2Ca<

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“…The reported value for La 2 CuO 4 at room temperature is ³14 (in which magnetic contribution is ³10) and ³4 W/(m·K) in in-plane (CuO 2 layer) and through-plane direction, respectively. 21) On the other hand, CuO 2 layer distances for La 2 CuO 4 and SrCuO 2 are 0.66 22) and 0.34 2) nm, respectively, which means that the SrCuO 2 has twice the number of spin thermal conductivity layers compared with the La 2 CuO 4 . Consequently, we expect that the in-plane value for SrCuO 2 reaches 2030 W/(m·K) while the through-plane value is limited to ³4 W/(m·K).…”

Section: ¹1mentioning

confidence: 99%

Post-annealing effects in two-dimensional spin system SrCuO<sub>2</sub> sputtered on glass substrate

Takahashi

Terakado

Yamazaki

et al. 2017

J. Ceram. Soc. Japan

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We prepared SrCuO 2 thin film by radio-frequency magnetron sputtering on glass substrate and have investigated its postannealing effects on structure and thermal conductivity. The as-sputtered film belongs to two-dimensional spin system SrCuO 2 , namely, layer-type SrCuO 2 , which has a possibility of exhibiting high, anisotropic thermal conductivity by magnetic excitation of the spins. It was found that the as-sputtered film has (001)-orientation in which the spin layers are parallel to the surface of substrate and that post-annealing results in enhancement of crystallinity of the film such as disappearance of grain boundaries, which can cause an increase in thermal conductivity.©2017 The Ceramic Society of Japan. All rights reserved.Key-words : SrCuO 2 , Sputtering, Thermal conductivity, Low-dimensional spin system, Active control of heat flow [Received December 25, 2016; Accepted February 21, 2017] The layer-type SrCuO 2 , which has been well known as a parent material of cuprate high-temperature superconductors, 1) has unique structure and characteristics:2),3) It contains alternativelystacked Sr and CuO 2 infinite layers. The CuO 2 layer exhibits a two-dimensional arrangement of antiferromagnetically-coupled spins of S = 1/2 in Cu 2+ , referred to as spin layers. Moreover, the spin structure is expected to yield high thermal conductivity parallel to the layers by the magnetic excitation. However, researches on the crystal have been limited to those concerning high-pressure synthesis and epitaxial growth on single crystal substrate. This is because the crystal belongs to a high pressure phase and accordingly is instable in ambient air.

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“…f-scans of all the n [14,38]. Although the nÊ=Ê1ÊÐÊ3 members of this series have been grown by bulk methods (in polycrystalline form) [27][28][29][30][31], this is the first thin film growth of these materials and the first report of phase-pure nÊ=Ê4 and nÊ=Ê5 phases in any form. We have studied the defect structure of these phases using HRTEM [38] as well as their dielectric properties [14].…”

Section: New Layered Compoundsmentioning

confidence: 99%

“…These compounds are known as Ruddlesden-Popper phases after the researchers who discovered the nÊ=Ê1 (Sr 2 TiO 4 ) and nÊ=Ê2 (Sr 3 Ti 2 O 7 ) members of this series [27]. [27][28][29][30][31]. The SrOÑTiO 2 phase diagram illustrates the difficulties in growing single crystals or epitaxial films of this series [32,33].…”

Section: New Layered Compoundsmentioning

confidence: 99%

“…These calculated enthalpies [35] show that there is no energetic driving force to favor the formation of one intermediate member over another. Instead, the final nanostructure of the crystal is determined by the local stoichiometry of the mixture on a nanometer scale, resulting in uncontrolled syntactic intergrowths [28]. Such intergrowths inhibit the characterization of the intrinsic electronic and optical properties of individual members of these series.…”

Section: New Layered Compoundsmentioning

confidence: 99%

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