¹⁷O and⁶³Cu NMR Investigations of High-<i>T</i>_cSuperconductorLa_1.85Sr_0.15CuO₄with<i>T</i>_c=38 K

Abstract

17 O and 63 Cu NMR measurements have been made in L 1.85 Sr 0.15 CuO 4 with T c =38 K. Both 17 O Knight shift and quadrupole tensor were determined from the analyses of the 17 O 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 YBa 2 Cu 3 O 7 with the electric field gradients due to the on-site holes at Cu and O sites. Then the weight factor of the Cu-3 d ( x 2 - y 2 ) and 2 p } 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 17 O and 63 Cu were almost the same as those in YBa 2 Cu 3 O 7 . Both shifts decrease significantly below T c having residual parts of 63 K ab =0.38% and 17 K c =0.02% at 4.2 K, which were larger than those in YBa 2 Cu 3 O 7 .