Structural implications of nuclear electric quadrupole splittings in high-Tc superconductors
Frank J. Adrian
DOI 10.1103/PhysRevB.38.2426 · Physical Review B
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Abstract
The electric field gradients and nuclear quadrupole coupling constants are calculated for La in La2CuO4, Eu in EuBa2Cu3O7, and Cu and Fe (as a replacement for Cu) in YBa2Cu3O7. We use an ionic model which regards the high-Tc superconductors as primarily ionic crystals modified by the introduction of a relatively small number of charge carriers via doping in La2CuO4 and non-stoichiometry in YBa2Cu3O7−δ for δ<0.5. Good agreement between theory and experiment is obtained for the spherically symmetric free-ion species La3+ and Eu3+ with distortion of the partially filled Eu3+ F04 state by the ionic crystal field playing an important role. Comparison of theory and experiment for the Cu and Fe cases suggests Cu is present largely as Cu2+ and supports the assignment of the low- and high-frequency nuclear quadrupole resonance lines to the chain and plane sites of YBa2Cu3O7, respectively, while Fe is present as a mixture of Fe2+ (ca. 25% to 50%) and Fe3+.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| La2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| (La1-xSrx)2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| EuBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| YBa2(Cu1-xFex)3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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