17O nuclear-magnetic-resonance spectroscopic study of high-Tc superconductors.

We have obtained solid-state $^{17}\mathrm{O}$ NMR spectra of a number of $^{17}\mathrm{enriched}$ oxides and high-temperature oxide superconductors, including ${\mathrm{Cu}}_{2}^{\mathrm{I}}$O, ${\mathrm{Cu}}^{\mathrm{II}}$O, ${\mathrm{KCu}}^{\mathrm{III}}$${\mathrm{O}}_{2}$, ${\mathrm{Bi}}_{2}$${\mathrm{O}}_{3}$, ${\mathrm{Tl}}_{2}$${\mathrm{O}}_{3}$, ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$, ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$, ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{x}}$, ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{x}}$, and ${\mathrm{Ba}}_{0.6}$${\mathrm{K}}_{0.4}$${\mathrm{BiO}}_{3}$. Spectra of all of the simple diamagnetic oxides contain relatively sharp resonances in a ``diamagnetic'' region of \ensuremath{\sim}-200 to +700 ppm (from ${\mathrm{H}}_{2}$O, International Union of Pure and Applied Chemistry \ensuremath{\delta} scale). ${\mathrm{Cu}}^{\mathrm{II}}$O exhibits a broad resonance centered at \ensuremath{\sim}4500 ppm.Spectra of all of the Cu-containing superconductors (at 300 K) contain a relatively broad and highly paramagnetically shifted peak, due to ${\mathrm{CuO}}_{2}$ planes, at \ensuremath{\approxeq}1800 ppm, together with a peak or series of peaks, in a more normal diamagnetic region, \ensuremath{\approxeq}100--600 ppm from ${\mathrm{H}}_{2}$O. ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ also contains a peak at \ensuremath{\sim}2950 ppm, assigned to the chain [O(4)] sites.The highly shifted (${\mathrm{CuO}}_{2}$) features undergo a \ensuremath{\approxeq}1000--1300 ppm diamagnetic shift in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ and ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{x}}$ upon cooling to 77 K (${T}_{c}$). These highly shifted features are absent in ${\mathrm{Ba}}_{0.6}$${\mathrm{K}}_{0.4}$${\mathrm{BiO}}_{3}$, although the resonance in ${\mathrm{Ba}}_{0.6}$${\mathrm{K}}_{0.4}$${\mathrm{BiO}}_{3}$ is \ensuremath{\approxeq}500 ppm paramagnetically shifted from that in the parent compound, ${\mathrm{BaBiO}}_{3}$. $^{17}\mathrm{O}$ NMR spectra of magnetically aligned samples of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ yield diagonal elements of the electric-field-gradient tensor (${\ensuremath{\chi}}_{\mathrm{ii}}$) for the ${\mathrm{CuO}}_{2}$ plane oxygens, O(2) and O(3), of \ifmmode\pm\else\textpm\fi{}(4.02,-6.46,2.44) and \ifmmode\pm\else\textpm\fi{}(3.95,-6.51,2.56) MHz.The observed resonance frequencies for both sites (${H}_{0}$\ensuremath{\parallel}c) are \ensuremath{\approxeq}1900 ppm from ${\mathrm{H}}_{2}$O. For the ${\mathrm{CuO}}_{2}$ plane in ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{x}}$ (at 300 K) and in ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{x}}$ (at 77 K) the quadrupole coupling constant (${e}^{2}$qQ/h) is \ensuremath{\approxeq}6.4 MHz also. For the column or bridging oxygen [O(1)] in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$, ${e}^{2}$qQ/h\ensuremath{\sim}7.3 MHz and \ensuremath{\eta}\ensuremath{\approxeq}0, at 300 K, the isotropic frequency shift is \ensuremath{\sim}458 ppm, and the anisotropy of the chemical or Knight shift (\ensuremath{\Delta}\ensuremath{\sigma}) is \ensuremath{\sim}657 ppm, with ${\ensuremath{\sigma}}_{?}$\ensuremath{\parallel}c. A similar result is found for the apical oxygen in ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$, with ${\ensuremath{\sigma}}_{33}$=${\ensuremath{\sigma}}_{?}$\ensuremath{\sim}694 ppm and ${\ensuremath{\sigma}}_{11}$=${\ensuremath{\sigma}}_{22}$=${\ensuremath{\sigma}}_{\ensuremath{\perp}}$\ensuremath{\sim}474 ppm, determined on a magnetically ordered sample. For the chain site in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ [O(4)], we find ${\ensuremath{\chi}}_{\mathrm{ii}}$=\ifmmode\pm\else\textpm\fi{}(3.38,-10.94,7.56) MHz. Calculations suggest for all sites that ${V}_{\mathrm{zz}}$ is negative and is aligned along the Cu-O-Cu bond axis. Results on oxygen-depleted ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ show considerable broadening of the plane-site features, consistent with the onset of antiferromagnetic ordering, while the column oxygens [O(1)] are much less affected. Temperature-dependence studies of ${T}_{1}$ for O(2,3) in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ indicate Korringa-type behavior above ${T}_{c}$, and the Knight shift predicted is in good accord with that observed.There is no BCS-type relaxation enhancement just below ${T}_{c}$. Overall, our results give a broad basis for the assignment of $^{17}\mathrm{O}$ NMR resonances in most of the classes of high-temperature superconductors currently being investigated (2:1:4, 1:2:3, ${\mathrm{Bi}}_{2}$${\mathrm{Cu}}_{2}$, ${\mathrm{Tl}}_{2}$${\mathrm{Cu}}_{2}$, and Cu-free Bi-containing phases) and show considerable similarities in frequency shifts (and their temperature dependence), ${T}_{1}$, ${e}^{2}$qQ/h values, and spin-echo decay behavior, for the ${\mathrm{CuO}}_{2}$ planes in each system, and between the (La(Sr)O,SrO,BaO) and (TlO,BiO) planes as well.