Physica C: Superconductivity and its applications

17O NMR study in aligned YBa2Cu4O8 powder

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We present 17O nuclear magnetic resonance (NMR) experiments in YBa2Cu4O8. Using an uniaxially oriented powder we were able to distinguish the four inequivalent oxygen sites in YBa2Cu4O8. The electric field gradient and the magnetic shift tensors have been determined at 100 K for all oxygen sites. Good agreement has been found between the experimental electric field gradient tensor and the one obtained from linearized augmented plane wave calculations. We further report on the temperature dependence of the in-plane and out-of-plane magnetic shift of the plane oxygens in the temperature range of 85-350 K. The results are compared with related data from YBa2Cu3O7 and YBa2Cu3O6.63. © 1992 Elsevier Science Publishers B.V. All rights reserved.