The magnetizations of the TM-doped TiO2 films decrease with increasing dopant content, which may be related to magnetic polarons in the samples. The final explanation on their magnetic properties still remains a puzzle, and the true mechanism deserves further study. Acknowledgements The authors are grateful to Professor Zhigao Hu, Jinzhong Zhang, Lin Peng, and Kai Jiang for the technical support. This work was supported partly
by Postdoctoral Science Foundation of Henan Province (2012021), the National Natural Science Foundation of China (60990312 and 61076060), Science and Technology Commission of Shanghai Municipality (10JC1404600), and Program for Changjiang Scholars and Innovative Research Team in University. References
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