NUCLEAR-RESONANCE PROPERTIES OF YBA2CU3O6+X SUPERCONDUCTORS

Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) results for copper-63, oxygen-17, and yttrium-89 nuclei in the superconducting composition range of YBa2Cu3O6+x (0.4 ≤x ≤1.0) are reviewed and interpreted. Copper NMR shift and susceptibility data, combined with a simple ionic model of local magnetic properties, yield a comprehensive analysis of the normal-state anisotropic susceptibility components and full characterization of the copper spin and orbital hyperfine couplings. Data on the spin-lattice relaxation time of these three nuclear species serve to characterize the highly correlated fermion dynamics in this system. Relaxation data from YBa2Cu3O7 (superconducting transition temperature Tc=90 K) and oxygen-deficient samples of this material (Tc ∼60 K) have been analyzed in terms of mean-field models incorporating short-range antiferromagnetic order, giving a quantitative account of (planar) relaxation for these three nuclei in terms of a single dynamical susceptibility.