Reduction of conductivity and ferromagnetism induced by Ag doping in ZnO:Co

TL;DR

This study investigates how Ag co-doping in ZnO:Co thin films affects their ferromagnetic properties and charge carrier concentration, revealing a decrease in ferromagnetism with increased Ag content due to defect clustering.

Contribution

It provides new insights into the relationship between Ag doping, charge compensation, and ferromagnetism in ZnO:Co, supported by both experimental and first-principles modeling.

Findings

Ag doping reduces native charge carriers in ZnO:Co.

Ferromagnetism decreases as Ag concentration increases.

Nano-cluster formation around Co impurities influences magnetic properties.

Abstract

Cobalt and silver co-doping has been undertaken in ZnO thin films grown by pulsed laser deposition in order to investigate the ferromagnetic properties in ZnO-based diluted magnetic materials and to understand the eventual relation between ferromagnetism and charge carriers. Hall transport measurements reveal that Ag doping up to 5% leads to a progressive compensation of the native n-type carriers. The magnetization curves show ferromagnetic contributions for all samples at both 5 K and room temperature, decreasing with increasing the Ag concentration. First principles modeling of the possible configurations of Co-Ag defects suggest the formation of nano-clusters around interstitial Co impurity as the origin of the ferromagnetism. The Ag co-doping results in a decrease of the total spin of these clusters and of the Curie temperature.