17O NMR measurements on superconducting Na0.35CoO2•yH2O

An O-17 NMR measurement was performed on nonoriented polycrystalline Na0.35CoO2 center dot yH(2)O with superconducting (SC) transition temperature T-C = 4.6 K. A weak temperature dependence was observed in the Knight shift at the 0 Site (K-17). The spin part of K-17 (K-17(spin)) is estimated from the plot of K-17 against bulk susceptibility chi. The K-17(spin) decreases in the SC state, indicative of the decrease in the inplane component of the spin susceptibility. The nuclear spin-lattice relaxation rate 1/T-1 at the Co site (59)(1/T-1) shows a good scaling with 1/T-1 at the Co Site 51(1/T-1). This indicates that the spin fluctuations at the 0 site originate from the Co spin dynamics. The relationships between 17(1/T1T) and 17 K-spin and between (17)(1/T1T) and 59(1/T1T) show the development of incommensurate fluctuations at q similar to 0 other than q = 0 below 30 K. A clear indication of ferromagnetic correlations at q = 0 was not observed from the present O-17 NMR studies.