63Cu NMR Evidence for Enhanced Antiferromagnetic Correlations around Zn Impurities in YBa2Cu3O6.7

Abstract

Doping the high-Tc, superconductor YBa2Cu3O6.7- with 1.5% of nonmagnetic Zn impurities in CuO2 planes is shown to produce a considerable broadening of 63Cu NMR spectra, as well as an increase of low-energy magnetic fluctuations detected in 63Cu spin-lattice relaxation measurements. A modelindependent analysis demonstrates that these effects are due to the development of staggered magnetic moments on many Cu sites around each Zn and that the Zn-induced moment in the bulk susceptibility might be explained by this staggered magnetization. Several implications of these enhanced antiferromagnetic correlations are discussed.