Ferromagnetism in laser deposited anatase Ti$_{1-x}$Co$_{x}$O$_{2-$\delta$}$ films

TL;DR

This study investigates Co-doped anatase TiO2 films, revealing high-temperature ferromagnetism linked to Co incorporation and clustering, suggesting potential for room-temperature spintronic applications.

Contribution

It demonstrates that Co-doped anatase TiO2 can exhibit intrinsic high-temperature ferromagnetism with Co matrix incorporation after annealing, advancing understanding of dilute magnetic semiconductors.

Findings

Co solubility limited to ~2% with cluster formation

Curie temperature exceeds 1180 K in as-grown samples

Annealing reduces Tc to around 650 K with full Co incorporation

Abstract

Pulsed laser deposited films of Co doped anatase TiO2 are examined for Co substitutionality, ferromagnetism, transport, magnetotransport and optical properties. Our results show limited solubility (up to ~ 2 %) of Co in the as-grown films and formation of Co clusters thereafter. For Ti0.93Co0.07O2-d sample, which exhibits a Curie temperature (Tc) over 1180 K, we find the presence of 20-50 nm Co clusters as well as a small concentration of Co incorporated into the remaining matrix. After being subjected to the high temperature anneal during the first magnetization measurement, the very same sample shows a Tc ~ 650 K and almost full matrix incorporation of Co. This Tc is close to that of as-grown Ti0.99Co0.01O2-d sample (~ 700 K). The transport, magnetotransport and optical studies also reveal interesting effects of the matrix incorporation of Co. These results are indicative of an intrinsic Ti1-xCoxO2-d diluted magnetic semiconductor with Tc of about 650-700 K.