Clues Obtained from the Oxygen Isotope Effect on NMR/NQR Parameters Observed in YBa2Cu4O8

Abstract

Nuclear magnetic and nuclear quadrupole resonance (NMR, NQR) techniques have a precision allowing one to determine rather small isotope effects. Well-defined oxygen stoichiometry and negligible oxygen diffusion makes YBa2Cu4O8 an ideal compound for studies of small isotope effects that require experimental results not hampered by reproducibility problems. We report on high-precision measurements of the temperature dependence of plane-63.65Cu NMR/NQR parameters such as Knight shift, spin-lattice relaxation rate R = 1/T1, NQR line frequency νQ and NQR linewidth δνQ, as well as 89Y Knight shift, performed in normal and superconducting 16O and 18O exchanged YBa2Cu4O8. ©2002 Plenum Publishing Corporation.