205Tl Knight and chemical shift in the high-Tc superconductors Tl2Ba2CuO6, Tl2CaBa2Cu2O8 and Tl2Ca2Ba2Cu3O10

Winzek, N.; Hentsch, F.; Mehring, M.; Mattausch, Hj.; Kremer, Reinhard K.; Simon, Arndt

doi:10.1016/0921-4534(90)90526-k

Cited by 20 publications

(11 citation statements)

References 37 publications

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“…Here we restrict ourselves to quoting some parameters which are needed in the data evaluation. The different samples of the T1 superconductors were prepared and characterized as described earlier [1,6,7]. The variation of the oxygen content 6 of Tl2Ba2CaCu2Os_ 91 was controlled by different heat treatment of the samples so that T c decreased from 101 K (sample 1) to 99 K (sample 2) and 85 K (sample 3) and inereased to 105 K (sample 4) [20].…”

Section: Methodsmentioning

confidence: 99%

“…Comparison of the T1-NMR data of the three compounds with n--1,2 and 3 facilitates a lot of information about the static and dynamic electronic stmcture of these systems [1][2][3][4][5][6][7][8][10][11][12][13][14][15][24][25][26][27][28][29][30][31][32][33]. In Fig.1 which displays the spectra of 2~ at room temperature already several features can be seen.…”

Section: 2~mentioning

confidence: 99%

“…So the components 2~ Evidence for Spin Gap 539 V I = 611 = 622 are expected to be sensitive to the interplanar spacing. With increasing n, the distance between the two T10-layers decreases and therefore the 611 = ~22 component of the chemical shift tensor also decreases [7].…”

Section: 2~mentioning

confidence: 99%

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205Tl NMR in the Cuprate Superconductor Tl2Ba2CaCu2O8−δ: Evidence for a pseudo spin gap

Winzek

Mehring

1992

Appl. Magn. Reson.

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2~ in Tl2Ba2Can_lCunOs_ 6 for different n and 6 is reviewed. For n = 2,3 the 2~ spectra consist of two lines. The main line arises from TI(l) in the TlO-layer whereas the defect line belongs to Tl(2) in the Ca-layers between the CuO2-1ayers. The temperature dependent Knight shift of the TI(2) (defect) line is caused by the hyperfine interaction with the CuOz-layer and is strongly related to the oxygen content of the sample. We find quasiparticle behavior for the TI(2) line similar to the 89y Knight shift in the YBa2Cu306+ £ system. In contrast the TI(l) line shows strong antiferromagnetic correlations with indication of pseudo spin gap opening above the superconducting transition temperature T c.

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Section: Methodsmentioning

confidence: 99%

Section: 2~mentioning

confidence: 99%

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205Tl NMR in the Cuprate Superconductor Tl2Ba2CaCu2O8−δ: Evidence for a pseudo spin gap

Winzek

Mehring

1992

Appl. Magn. Reson.

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“…Note also that the minimum Sr content required for superconductivity is unknown and, owing to the non-insulating end material at x = 0 (i.e., x 0 is unknown) [11], it presently remains infeasible to apply the charge allocation methodology in calculating σ for Tl 0.7 LaSrCuO 5 . [44]; Knight shift data for all three of these compounds also show trivalent Tl [36]. Consequently, the valency scaling γ-factor for these compounds is the product of 1/2 given for +3 valence from rule (2a) and 2 from the double-layer structural stoichiometry according to rule (2b) such that,…”

Section: +3mentioning

confidence: 99%

Superconducting interaction charge in thallium-based high-TC cuprates: Roles of cation oxidation state and electronegativity

Harshman

Fiory

2015

Journal of Physics and Chemistry of Solids

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Superconductivity in the Tl-based cuprates encompasses a notably broad range of measured optimal transition temperatures T C0 , ranging from lowest in the charge-depleted Tl-1201 compounds (Tl 1-x (Ba/Sr) 1+y La 1-y CuO 5-δ ), such as Tl 0.7 LaSrCuO 5 (37 K) and TlBa 1.2 La 0.8 CuO 5 (45.4 K), to highest in the Tl-1223 compound TlBa 2 Ca 2 Cu 3 O 9±δ (133.5 K). Seven Tl-based cuprates are considered and compared using the model of superconductive pairing via electronic interactions between two physically separated charge reservoirs, whereis determined by the superconducting interaction charge fraction σ, the number η of CuO 2 layers, and the basal-plane area A, each per formula unit, and the transverse distance ζ between interacting layers. Herein it is demonstrated that σ follows from the elemental electronegativity and the oxidation state of Tl, and other structurally analogous cations. The comparatively lower elemental electronegativity of Tl, in conjunction with its oxidation state, explains the higher σ and T C0 values in the Tl-based compounds relative to their Bi-based cuprate homologues. A derivation of σ is introduced for the optimal Tl 2 Ba 2 Ca η-1 Cu η O 2η+4 (for η = 1, 2, 3) compounds, which exhibit a Tl oxidation state at or near +3, obtaining the fundamental value σ 0 = 0.228 previously established for YBa 2 Cu 3 O 6.92 . Also reported is the marked enhancement in σ associated with Tl +1 and analogous inner-layer cations relative to higher-valence cations. For a model proposition of σ = σ 0 , the fractional Tl +1 content of the mixed-valence compound, TlBa 2 Ca 2 Cu 3 O 9±δ , is predicted to be 1/3 at optimization, in agreement with existing data. Charge depletion is illustrated for the two Tl-1201 compounds, where σ < σ 0 values are determined according to substitution of Ba , and/or Tl depletion. Additionally, statistical analysis of calculated and experimental transition temperatures of 48 optimal superconductors shows an absence of bias in determining σ, A, and ζ.

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“…This work is closely related to the study on oriented powders of Mehring et al [6][7][8][9][10]. Measurements of the linewidth were performed for HII the c-axis and HI c. Because of the very high anisotropy of the material, it is difficult ir not impossible to obtain reliable linewidth data for H_l_ c in the superconducting state.…”

Section: Introductionmentioning

confidence: 99%

Study of the vortex dynamics in single crystals of the high-T c superconductor Tl2Ba2CaCu2O8 via205Tl NMR

1992

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The 2~ linewidth in single crystals of the high-T c superconductor T12Ba2CaCu208 (T c = 105 K) is analyzed for the normal (N) and impurity (I) Tl-sites. On the I-sites Ca has been replaced by TI. Measurements were performed in a field of 4.7 T. The normal state linewidth on the N and I sites is shown to be mainly determined by a distribution in Knight shifts. To simulate the final increase below 50 K we have studied the vortex lattice in a single superconducting sheet by a molecular dynamics method for systems up to 2000 vortices. The results compare well with the experimental data. This implies that the temperature dependence of the linewidth in this highly anisotropic material is determined by flux dynamics and only marginally by the temperature dependence of the penetration depth.

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205Tl Knight and chemical shift in the high-Tc superconductors Tl2Ba2CuO6, Tl2CaBa2Cu2O8 and Tl2Ca2Ba2Cu3O10

Cited by 20 publications

References 37 publications

205Tl NMR in the Cuprate Superconductor Tl2Ba2CaCu2O8−δ: Evidence for a pseudo spin gap

205Tl NMR in the Cuprate Superconductor Tl2Ba2CaCu2O8−δ: Evidence for a pseudo spin gap

Superconducting interaction charge in thallium-based high-TC cuprates: Roles of cation oxidation state and electronegativity

Study of the vortex dynamics in single crystals of the high-T c superconductor Tl2Ba2CaCu2O8 via205Tl NMR

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