O17NMR spectroscopy of magnetically orderedYBa2Cu3O7−xmicrocrystals

Autor: Linda Reven, Emannuel Ramli, Eric Oldfield, Thomas B. Rauchfuss, Hee Cheon Lee, Chris Coretsopoulos
Rok vydání: 1989
Předmět:
Zdroj: Physical Review B. 39:781-784
ISSN: 0163-1829
DOI: 10.1103/physrevb.39.781
Popis: We have obtained $^{17}\mathrm{O}$ nuclear-magnetic-resonance spectra of powder samples of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$ and $\mathrm{Eu}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$, as well as magnetically ordered $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$. Two major features are observed in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$: a sharp resonance at \ensuremath{\simeq}1800 ppm (from external ${\mathrm{H}}_{2}^{17}$O, International Union of Pure and Applied Chemistry $\ensuremath{\delta}$ scale) and a broader series of features centered at \ensuremath{\simeq}400 ppm. The 1800-ppm feature undergoes a diamagnetic shift of \ensuremath{\simeq}800 ppm on cooling to 77 K, and a similar magnitude shift on Eu substitution, suggesting assignment to the plane oxygens, O(2,3). Measurements on magnetically ordered samples at 8.45 and 11.7 T give the magnitude of the diagonal terms of the electric-field-gradient tensor, which are 2.3, 3.5, and 5.8 MHz. For the column oxygen, O(1), we find $\frac{{e}^{2}\mathrm{qQ}}{h}=7.7$ MHz, with a chemical shift anisotropy of \ensuremath{\simeq}660 ppm.
Databáze: OpenAIRE