NMR AND NEUTRON-SCATTERING EXPERIMENTS ON THE CUPRATE SUPERCONDUCTORS- A CRITICAL REEXAMINATION

We show that it is possible to reconcile NMR and neutron-scattering ex periments on both La(2-x)Sr(x)Cuo(4) and YBa2Cu3O6+x, by making use of the Millis-Monien-Pines mean-field phenomenological expression for th e dynamic spin-spin response function, and re-examining the standard S hastry-Mila-Rice hyperfine Hamiltonian for NMR experiments. The recent neutron-scattering results of Aeppli et al. on La1.86Sr0.14CuO4 are s hown to agree quantitatively with the NMR measurements of T-63(1) and the magnetic scaling behavior proposed by Barzykin and Pines. The reco nciliation of the O-17 relaxation rates with, the degree of incommensu ration in the spin-fluctuation spectrum Seen in neutron experiments is achieved by introducing, a transferred hyperfine coupling C' between O-17 nuclei and their next-nearest-neighbor Cu2+ spins; this leads to a near-perfect cancellation of the influence of the incommensurate spi n-fluctuation peaks on the O-17 relaxation rates of La2-xSrxCuO4. The inclusion of the C' term also leads to a natural explanation, within t he one-component model, the different temperature dependence of the an isotropic O-17 relaxation rates for different field orientations, rece ntly observed by Martindale et al. The measured significant decrease w ith doping of the anisotropy ratio, (63)R=T-63(1ab)/T-63(1c) in the La 2-xSrxCuO4 system, from (63)R=3.9 for La2CuO4 to (63)R similar or equa l to 3.0 for La1.85Sr0.15CuO4 is made compatible with the doping depen dence of the shift in the incommensurate spin-fluctuation peaks measur ed in neutron experiments', by suitable choices of the direct and tran sferred hyperfine coupling constants A(beta) and B.