Nuclear quadrupole resonance and nuclear magnetic resonance of copper in the high-Tc superconductor YBa2Cu3O7

The Cu65 and Cu63 zero-field nuclear quadrupole resonance (NQR), nuclear magnetic resonance at 4.7 and 8.5 T, and the spin-lattice relaxation time T1 at 8.5 T are measured in the superconducting oxide YBa2Cu3O7 between 80 and 300 K. No sign of magnetic order or localized moments is found. The NQR linewidth is strongly dependent on the oxygen content. We assign the Cu63 NQR line at 22 MHz to the Cu site with oxygen coordination 5; T1 is dominated by the quadrupolar relaxation due to spin-phonon coupling.