Effect of oxygen content on the transport properties and magnetoresistance in [Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$] single crystals

TL;DR

This study explores how varying oxygen content affects the transport properties and magnetoresistance in single crystals of a cobalt oxide compound, revealing magnetic and electronic phase transitions influenced by oxygen levels.

Contribution

It provides new insights into the relationship between oxygen content and magnetic/electronic properties in cobalt oxide single crystals, including the observation of an insulator-metal transition.

Findings

Resistivity minimum shifts with oxygen loss, indicating SDW enhancement.

Large negative magnetoresistance observed across samples.

Magnetic-field-driven insulator-metal transition in oxygen-annealed samples.

Abstract

Transport property is investigated in [Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$] single crystals obtained by varying annealing conditions. The $\rho_{ab}(T)$ exhibits a resistivity minimum, and the temperature corresponding to this minimum increases with the loss of oxygen content, indicative of the enhancement of spin density wave (SDW). Large negative magnetoresistance (MR) was observed in all single crystals [Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$], while a magnetic-field-driven insulator-to-metal (IM) transition in oxygen annealed samples. These results suggest a ferromagnetic correlation in system enhanced by oxygen content. In addition, a low temperature thermal activation resistivity induced by fields was observed in single crystals annealed in oxygen atmosphere.