NMR measurement of the exchange coupling between Cu(2) atoms in YBa2Cu3O7- delta (Tc=90 K).

Abstract

The authors report the transverse NMR relaxation of chain [Cu(1)] and plane [Cu(2)] nuclei in a single crystal of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (${T}_{c}=90$ K) in the normal state. They demonstrate the existence of a strong indirect spin-spin coupling between Cu(2) nuclei, and show that it can be explained using a model in which the Cu(2) atoms possess electronic magnetic moments which are exchange coupled to one another. In such a model, the strength of the coupling implies an effective electronic exchange coupling ${J}_{\mathrm{eff}}\ensuremath{\approx}1100$ ${\mathrm{cm}}^{\ensuremath{-}1}$.