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Originally published in Science Express on 11 January 2001
Science 2 February 2001:
Vol. 291. no. 5505, pp. 854 - 856
DOI: 10.1126/science.1056186
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Reports

Room-Temperature Ferromagnetism in Transparent Transition Metal-Doped Titanium Dioxide

Yuji Matsumoto,1 Makoto Murakami,1 Tomoji Shono,1 Tetsuya Hasegawa,1 Tomoteru Fukumura,2 Masashi Kawasaki,2 Parhat Ahmet,3 Toyohiro Chikyow,34 Shin-ya Koshihara,5 Hideomi Koinuma1367*

Dilute magnetic semiconductors and wide gap oxide semiconductors are appealing materials for magnetooptical devices. From a combinatorial screening approach looking at the solid solubility of transition metals in titanium dioxides and of their magnetic properties, we report on the observation of transparent ferromagnetism in cobalt-doped anatase thin films with the concentration of cobalt between 0 and 8%. Magnetic microscopy images reveal a magnetic domain structure in the films, indicating the existence of ferromagnetic long-range ordering. The materials remain ferromagnetic above room temperature with a magnetic moment of 0.32 Bohr magnetons per cobalt atom. The film is conductive and exhibits a positive magnetoresistance of 60% at 2 kelvin.

1 Ceramics Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
2 Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502, Japan.
3 National Institute for Research in Inorganic Materials, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
4 National Research Institute for Metals, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan.
5 Department of Materials Science, Tokyo Institute of Technology, 2-12-1 Okayama, Meguro-ku, Tokyo, Japan, and Kanagawa Academy of Science and Technology, KSP East Building 301, 3-2-1 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa, 213-0012, Japan.
6 Frontier Collaborative Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
7 CREST-Japan Science and Technology, Waseda University, 55th Building, 3-4-1 Ohkubo, Shinjyuku-ku 169-8555, Japan.
*   To whom correspondence should be addressed. E-mail: koinuma{at}oxide.rlem.titech.ac.jp

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Spintronics: A Spin-Based Electronics Vision for the Future.
S. A. Wolf, D. D. Awschalom, R. A. Buhrman, J. M. Daughton, S. von Molnar, M. L. Roukes, A. Y. Chtchelkanova, and D. M. Treger (2001)
Science 294, 1488-1495
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Science. ISSN 0036-8075 (print), 1095-9203 (online)