17-O NMR studies of a triangular-lattice superconductor Na{x}CoO{2}yH{2}O

We report the first 17-O NMR studies of a triangular-lattice superconductor Na{1/3}CoO{2}-[4/3]H{2}O and the host material Na{x}CoO{2} (x=0.35 and 0.72). Knight shift measurements reveal that p-d hybridization induces sizable spin polarization in the O triangular-lattice layers. Water-intercalation makes CoO{2} planes homogeneous, and enhances low frequency spin fluctuations near T{c}=4.5 K at some finite wave-vectors different from both the ferromagnetic and ``120 degree'' modes.