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Title:Oxygen-17 nuclear magnetic resonance studies of high-temperature superconductors
Author(s):Coretsopoulos, Christopher Nicholas
Doctoral Committee Chair(s):Oldfield, Eric
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Chemistry, Physical
Physics, Condensed Matter
Abstract:This study presents $\sp{17}$O NMR spectra of randomly and magnetically oriented samples of various high-$T\sb{c}$ superconductors. Systems under investigation include: (BaK)BiO$\sb3$, La$\sb{1.85}$Sr$\sb{0.15}$CuO$\sb4$, YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$, Bi$\sb2$Sr$\sb2$CaCu$\sb2$O$\sb8$ and Tl$\sb2$Ba$\sb2$CaCu$\sb2$O$\sb8$. Measurements of the angular dependence of the oxygen frequency shifts and corresponding satellite transitions have enabled us to assign the oxygen sites of magnetically oriented YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$, as well as determine the e.f.g. parameters for various sites. The temperature and angular dependence of the oxygen frequency shifts and relaxation rates have been studied as well as the effect of the oxygen stoichiometry and rare earth substitutions. Finally, we have compared the $\sp{17}$O frequency shifts of YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ to those of the precursor oxides, and other high-$T\sb{c}$ compounds, and have consistently observed a paramagnetically shifted feature associated with the CuO$\sb2$ planes ($\sim$2000 ppm from H$\sb2$O) and a second feature or set of features in the diamagnetic region (typically at $\sim$400 ppm from H$\sb2$O) which are attributed to sites other than the CuO$\sb2$ planes. Precursor effects in the normal phase of YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ are investigated, pointing strongly to antiferromagnetic fluctuations which may persist in the superconductive phase.
Issue Date:1989
Rights Information:Copyright 1989 Coretsopoulos, Christopher Nicholas
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9010838
OCLC Identifier:(UMI)AAI9010838

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