Feffornagnetism at 300 K in spin-coated films of Co doped anatase and rutile-TiO2

Thin films of Ti1-xCoxO2 (x = 0 and 0.03) have been prepared on sapphire substrates by spin-on technique starting from metalorganic precursors. When heat treated in air at 550 and 700 degreesC, respectively, these films present pure anatase and rutile structures as shown both by X-ray diffraction and Raman spectroscopy. Optical absorption indicate a high degree of transparency in the visible region. Such films show a very small magnetic moment at 300 K. However, when the anatase and the rutile films are annealed in a vacuum of 1 x 10(-5) Torr at 500 and 600 degreesC, respectively, the magnetic moment, at 300 K, is strongly enhanced reaching 0.36mu(B)/Co for the anatase sample and 0.68mu(B)/Co for the rutile one. The ferromagnetic Curie temperature of these samples is above 350 K. (C) 2004 Elsevier Ltd. All rights reserved.