{sup 63}Cu and {sup 89}YNMR study of an optimally doped YBa{sub 2}Cu{sub 3}O{sub 6.94} single crystal
- Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, C.P. 369, 13560-970 Sao Carlos-SP (Brazil)
- Grenoble High Magnetic Field Laboratory, Max-Planck-Institut fuer Festkoerperforschung and Centre National de la Recherche Scientifique, B.P. 166, 38042 Grenoble Cedex 9 (France)
- Laboratoire de Spectromerie Physique, Universite Joseph Fourier Grenoble I, B.P. 87, 38402 St.-Martin dHeres (France)
- Departement de Recherche Fondamentale, Centre dEtudes Nucleaires de Grenoble, B.P. 85X, 38041 Grenoble Cedex (France)
We report {sup 63}Cu spin-spin and spin-lattice relaxation rates ({sup 63}T{sub 2}{sup {minus}1} and {sup 63}T{sub 1}{sup {minus}1}) and {sup 89}Y magnetic hyperfine shift ({sup 89}K) in the normal state of an optimally doped single-crystalline sample YBa{sub 2}Cu{sub 3}O{sub 6.94} with T{sub c}=93 K (which corresponds to the maximal T{sub c} for the YBa{sub 2}Cu{sub 3}O{sub 6+x} family). The comparison between ({sup 63}T{sub 1}T){sup {minus}1} and ({sup 63}T{sub 2g}){sup {minus}1} evidences that the spin pseudogap does {ital not} open above T{sub c} at optimal doping, although the static spin susceptibility starts to decrease well above T{sub c}, at T{sub 0}=150 K. Comparing the NMR data of this optimally doped sample with those of two other {open_quotes}90 K{close_quotes} samples previously studied by our group, an underdoped YBa{sub 2}Cu{sub 3}O{sub 6.92} and an overdoped YBa{sub 2}C{sub 3}O{sub 7}, strongly suggests that the crossover to the spin pseudogap regime occurs precisely at the optimal doping level. A phenomenological phase diagram based on the NMR results in the normal states is proposed. We discuss to which extent our data agree with the predictions of the magnetic scaling theory. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 544926
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 17 Vol. 56; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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