$^{23}$Na NMR Study of Layered Superconductor $Na_xCoO_2- yH_2O$

TL;DR

This study uses $^{23}$Na NMR to investigate the local electronic environment and spin dynamics in layered $Na_xCoO_2-yH_2O$ superconductors, revealing how water intercalation affects magnetic properties.

Contribution

It provides the first detailed $^{23}$Na NMR analysis comparing superconducting and non-superconducting hydrate phases, highlighting water's impact on local magnetic shielding and relaxation.

Findings

Different $^{23}$Na shifts indicate varying shielding effects.

Relaxation rates differ significantly between phases.

Water intercalation influences magnetic properties.

Abstract

We measured $^{23}$Na-NMR spectra and nuclear spin-lattice relaxation rates $^{23}(1/T_1)$ of superconducting and non-superconducting bilayer hydrate $Na_xCoO_2-yH_2O$ (x ~ 0.3, y ~ 1.3). The central resonance frequency shows a small but various shift due to the difference in the shielding effect by intercalated $H_2O$ molecules. The different shielding effect also gives a large difference in the magnitude of $^{23}(1/T_1)$.