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

TL;DR

This study uses 17-O NMR to investigate the magnetic properties of a triangular-lattice superconductor Na{x}CoO{2}yH{2}O, revealing water-induced homogeneity and enhanced spin fluctuations near the superconducting transition.

Contribution

First 17-O NMR analysis of the superconductor Na{x}CoO{2}yH{2}O, showing water's role in homogeneity and spin fluctuation enhancement.

Findings

Water intercalation makes CoO2 planes homogeneous.

Spin fluctuations are enhanced near T_c at finite wave-vectors.

p-d hybridization induces significant spin polarization in O layers.

Abstract

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.