¹⁷O and ⁶³Cu NMR Investigations of High-T_c Superconductor La_1.85Sr_0.15CuO₄ with T_c=38 K

抄録

¹⁷O and ⁶³Cu NMR measurements have been made in L_1.85Sr_0.15CuO₄ with T_c=38 K. Both ¹⁷O Knight shift and quadrupole tensor were determined from the analyses of the ¹⁷O spectrum of oriented powder. The quadrupole frequencies of the planar oxygen and Cu nuclei are consistently interpreted by the analyses of Hanzawa et al. made in YBa₂Cu₃O₇ with the electric field gradients due to the on-site holes at Cu and O sites. Then the weight factor of the Cu-3d(x²−y²) and 2p_σ wave functions are deduced, the latter having the larger weight. From the Knight shifts vs the bulk susceptibility plots, the hyperfine coupling constants for ¹⁷O and ⁶³Cu were almost the same as those in YBa₂Cu₃O₇. Both shifts decrease significantly below T_c having residual parts of ⁶³K_ab=0.38% and ¹⁷K_c=0.02% at 4.2 K, which were larger than those in YBa₂Cu₃O₇.