On The Application of Antiferromagnetic Fermi Liquid Theory to NMR Experiments on YBa2 Cu3 O6.63

H. Monien, D. Pines, and M. Takigawa

90-015

NMR experiments on the YBa$_2$Cu$_3$O$_{6.63}$ material provide an important test of the antiferromagnetic Fermi liquid model for the spin-spin correlation function proposed by A. Millis, H. Monien, and D. Pines. We show that their theory provides a quantitative fit, with parameters determined from experiment, to the NMR experiments of Takagawa et al. on the Cu(2), O(2,3) nuclei, and of Alloul et al. on the Y nuclei in the YBa$_2$Cu$_3$O$_{6.63}$ material. We find that the hyperfine couplings do not change in going from the YBa$_2$Cu$_2$O$_7$ to the YBa$_2$Cu$_2$O$_{6.63}$ material whereas the antiferromagnetic correlation is increased. We present results for the changes in relevant magnetic parameters brought about by reducing the oxygen content from YBa$_2$Cu$_3$O$_7$ to YBa$_2$Cu$_3$O$_{6.63}$ and discuss the implications of a small energy scale $hw_{sf} < k_B T_c$ emerging from the analysis of the NMR experiments. Our results support the proposal by Pines that the excitations in the normal state of superconducting YBCO are best described as those of an antiferromagnetic Fermi liquid and suggest that this description is applicable to other cuprate oxide superconductors.