NMR-STUDY OF THE SPIN DYNAMICS IN TL2BA2CUOY (TC=85 K)

In order to understand the spin dynamics in the over-doped region of the high-T(c) oxides, the temperature (7) dependence of the Knight shift and the spin-lattice relaxation time (T1) at the Cu and the O sites of the CuO2 plane were measured in the normal state of Tl2Ba2CuOy with maximum T(c) (T(c) = 85 K). The T dependence of the Knight shift at the O site is almost isotropic. In addition, the transferred hyperfine coupling constant is estimated to be fairly large at the Cu site. These facts indicate that the hybridization between the Cu 3d and the O 2p is strong in Tl2Ba2CuOy and the doped holes do not have strong O 2p character. The T dependence of the Knight shift at the O site is the same as that of the Cu site, suggesting that the single-spin-component model is likely in this over-doped system. Based on a comparison between the T1 of the Cu and the O sites, the antiferromagnetic correlation is considered to be very weak in this system, and the antiferromagnetic correlation length (xi/a) is estimated to be 1.2 at 120 K. Although the reason is unclear, the so-called psuedo-spin-gap behavior is observed below 120 K at the Cu site, and the relation T1TK=const was found to be more likely at the O site than the Korringa-type relation. In addition, the ratio of the T1 at the Cu and the O sites becomes T independent in the vicinity of the T(c). These phenomena are also observed in the lightly doped system; thus they may be considered as universal features of the high-T(c) oxides.