Room temperature magnetization in Co-doped anatase phase of TiO₂

¹ Department of Physics, Vali-e-Asr University of Rafsanjan, 77139-36417 Rafsanjan, Iran
² Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
³ Department of Engineering Sciences, Ångström Laboratory, Uppsala University, P.O. Box 534, SE-75121 Uppsala, Sweden
⁴ Department of Physics, Moi University, P.O. Box 1125, Eldoret, Kenya
⁵ Nano research Centre, Faculty of Basic Sciences, Ferdowsi University of Mashhad, Mashhad, Iran

^a e-mail: masoud.karimipour@gmail.com

Received: 20 June 2012
Revised: 3 October 2012
Accepted: 7 December 2012
Published online: 31 January 2013

Abstract

Co_xTi_1–xO₂ films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at 475 °C. A hydro-alcoholic solution containing titanium (iv) isopropoxide and Co(NO₃)₂ with various Co doping levels from x = 0–0.015 in solution was used as spray solution. Grazing incident angle of X-ray diffraction illustrates that the Co_xTi_1–xO₂ films are single phase and polycrystal with mixed orientations. Study of surface morphology of the films by atomic force microscope reveals that the annealing atmosphere does not significantly affect the grain size and the microstructure of the films. This study provides further insight into the importance of annealing atmosphere on magnetization of the films. Room temperature magneto-optical Kerr measurement was employed in polar mode. A hysteresis loop and a paramagnetic behavior have been recorded for samples annealed in H₂ ambient gas and air, respectively. Chemical composition analysis by X-ray photo-electron spectroscopy showed that Co atoms are bounded to oxygen and no metallic clusters are present. Moreover, it indicates the formation of high spin Co²⁺ for the sample x = 0.008 annealed in H₂ ambient gas. The origin of magnetization can be attributed to the contribution of oxygen vacancies in the spin polarization of the structure.