Evidence of carrier mediated room temperature ferromagnetism in transparent semiconducting Sn1-xCoxO2-δ thin films

Magnetic ordering in Co-substituted spray pyrolyzed SnO2 thin films has been investigated by magneto-transport studies of Sn1-xCoxO2-δ and F co-doped films. The free carrier concentration and room temperature ferromagnetism induced in Sn1-xCoxO2-δ thin films with cobalt concentrations up to x = 0.10 are found to be closely related to each other. Both the carrier concentration and the saturation magnetic moment increase monotonically with the concentration of Co, and attain maximum values of 2.2 x 1019 cm-3 and 0.26 μB/Co-ion, respectively, at x = 0.10. The substitution of O2- with F- (nearly 10 atomic percent (a/o)) has resulted in much higher values of both carrier concentration (2.07 x 1020 cm-3) and magnetic moment (0.80 μB/Co-ion). Also, anomalous behavior of the Hall effect has been observed. The carrier mediated interaction is proposed to be the most probable mechanism responsible for ferromagnetism in these films. The temperature dependence of the magnetization of these films predicts a Curie temperature exceeding 573 K. All the films are optically transparent (>75%) in the visible spectral region