17O and63Cu NMR Investigations of High-TcSuperconductorLa1.85Sr0.15CuO4withTc=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 .