super(17)O NMR in YBa sub(2)Cu sub(3)O sub(7- delta ) superconductors

• Published in: Europhysics letters Vol. 8; no. 4; pp. 363 - 368
• Main Authors: Wzietek, P, Koengeter, D, Auban, P, Jerome, D, Bassat, J M, Coutures, J P, Dubois, B, Odier, Ph
• Format: Journal Article
• Language: English
• Published: 01.01.1989
• ISSN: 0295-5075

The authors present the first super(17)O NMR data obtained in YBa sub(2)Cu sub(3)O sub(7- delta ) powder with T sub(c) = 90 K in which oxygen sites on Cu-O chains had been selectively populated by a gas exchange process performed at low temperature. A comparison between fully exchanged and chain only exchanged samples suggests that magnetic-field-swept spectra cannot discriminate between both kinds of samples. Fourier-transformed spectra do however provide a very clear assignment between plane and chain-bridge sites. The spin-lattice relaxation of chain sites measured between 4.2 and 300 K is dramatically nonexponential, as expected for nuclei in the presence of an important quadrupolar interaction. The data show the existence of a shortening of the chain relaxation in a limited temperature domain slightly below T sub(c).