Ferromagnetism in laser deposited anatase Ti$_{1-x}$Co$_{x}$O$_{2-$δ$}$ films
Abstract
Pulsed laser deposited films of Co doped anatase TiO2 are examined for Co substitutionality, ferromagnetism, and transport 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). These results indicate that the true Ti1-xCoxO2-d diluted magnetic semiconductor has a Tc of about 650 to 700 K.Keywords
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