Magnetic susceptibility study of hydrated and non-hydrated NaxCoO2-yH2O single crystals

TL;DR

This study investigates the magnetic susceptibility of hydrated and non-hydrated NaxCoO2 single crystals, revealing anisotropic behavior, composition-dependent g-factor ratios, and effects of hydration on magnetic properties.

Contribution

It provides new insights into the anisotropic magnetic properties and the impact of hydration on NaxCoO2 single crystals, including the behavior of localized spins.

Findings

Hydrated samples show higher susceptibility than non-hydrated ones.

Anisotropic g-factor ratio decreases with decreasing x.

Hydration introduces additional localized spins.

Abstract

We have measured the magnetic susceptibility of single crystal samples of non-hydrated NaxCoO2 (x ~ 0.75, 0.67, 0.5, and 0.3) and hydrated Na0.3CoO2-yH2O (y ~ 0, 0.6, 1.3). Our measurements reveal considerable anisotropy between the susceptibilities with H||c and H||ab. The derived anisotropic g-factor ratio (g_ab/g_c) decreases significantly as the composition is changed from the Curie-Weiss metal with x = 0.75 to the paramagnetic metal with x = 0.3. Fully hydrated Na0.3CoO2-1.3H2O samples have a larger susceptibility than non-hydrated Na0.3CoO2 samples, as well as a higher degree of anisotropy. In addition, the fully hydrated compound contains a small additional fraction of anisotropic localized spins.