Propriedades estruturais e magnéticas de filmes finos de Ti 1-x Co x O produzidos por sol-gel e spin coating

Abstract

Ti 1-x Co x O 2 (x=0-0,10) thin films for three different TiO molar ratio 0,3mol/L, 0,5mol/L, 0,7mol/L, were prepared by sol-gel and spin coating, and their structural and magnetic properties were characterized. In this work it was mainly investigated the effect of Co dopant and Ti molar ratio on the structural and magnetic properties of Ti 1-x Co x O 2 2 films. The diffractograms obtained by XRD showed that the magnetic Co impurity atoms entered into the TiO lattice causing a phase transition from anatase to rutile. When dopant concentration and Ti molar ratio is high, CoTiO 2 secondary phase was observed. XRR measurements showed that films thickness is between 100-220nm, with some roughness and less dense than bulk rutile. Vibrating sample magnetometer measurement showed that the films have ferromagnetic behavior at room temperature. The maximum value of the spontaneous magnetic moment per volume (M) was 18,3emu/cm 3 for a dopant concentration of 3at% and Ti molar ratio 0,5mol/L. It is found that ferromagnetic behaves strongly depend of dopant concentration and Ti molar ratio, being optimized for low values of both. In addition, a crystalline, thinner and low roughness structure improves the magnetization of the films. The predominance of rutile phase contributes to increase the magnetization of the TiO . Finally, the low value of M obtained in this work, comparing with the Co bulk value, means that Co ions were well distributed into the TiO 2 lattice, without any presence of Co clusters neither secondary phases to low dopant level ≤5at% and low Ti molar ratio ≤5mol/L, reducing a possibility that room temperature ferromagnetic could be produced by Co clusters, while secondary phases are factors that reduce the magnetization.