NMR and NQR Studies of17O and63Cu in CuO2Plane of High-TcYBa2Cu3O6.65withTc=61 K

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Abstract
The microscopic property of each oxygen and copper site in the CuO 2 plane of YBa 2 Cu 3 O 6.65 with T c =61 K has been investigated by 17 O NMR and 63 Cu NQR techniques. It has been found that the nuclear spin-lattice relaxation rate 1/ T 1 for Cu sites is depressed by three orders of magnitude as compared with that for YBa 2 Cu 3 O 7 with T c =92 K, whereas 1/ T 1 for oxygen sites exhibits a rather small change, decreasing approximately to one-fourth (1/4). From this difference of the relaxation behavior between oxygen and Cu sites, it is derived that the progressive reduction of 1/ T 1 for oxygen sites is responsible for the decrease of the p -hole carriers, while the extraordinary decrease of 1/ T 1 for Cu sites is due to the dramatic suppression of the low-frequency components of an antiferromagnetic spin fluctuation of nearly localized d electrons. The spin fluctuation at the Cu sites is found to strongly correlate with the p -hole content.