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Origin and control of high-temperature ferromagnetism in semiconductors

Nature Materials volume 6, pages 440446 (2007) | Download Citation

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Abstract

The extensive experimental and computational search for multifunctional materials has resulted in the development of semiconductor and oxide systems, such as (Ga,Mn)N, (Zn,Cr)Te and HfO2, which exhibit surprisingly stable ferromagnetic signatures despite having a small or nominally zero concentration of magnetic elements. Here, we show that the ferromagnetism of (Zn,Cr)Te, and the associated magnetooptical and magnetotransport functionalities, are dominated by the formation of Cr-rich (Zn,Cr)Te metallic nanocrystals embedded in the Cr-poor (Zn,Cr)Te matrix. Importantly, the formation of these nanocrystals can be controlled by manipulating the charge state of the Cr ions during the epitaxy. The findings provide insight into the origin of ferromagnetism in a broad range of semiconductors and oxides, and indicate possible functionalities of these composite systems. Furthermore, they demonstrate a bottom-up method for self-organized nanostructure fabrication that is applicable to any system in which the charge state of a constituent depends on the Fermi-level position in the host semiconductor.

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Acknowledgements

This work was partially supported by the Grant-in-Aids for Scientific Research (Basic Research (B) and Priority Areas), the 21st COE program of the University of Tsukuba and the ‘Nanotechnology Support Project’ of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. We would like to thank N. Ozaki, S. Marcet, T. Kumekawa, K. Kadowaki (University of Tsukuba), O. Eryu (Nagoya Institute of Technology) and T. Ohshima (Japan Atomic Energy Agency) for contributions and support in the experiments. T.D. thanks A. Bonanni, F. Matsukura, H. Ohno and M. Sawicki for valuable discussions.

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Affiliations

  1. Institute of Materials Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8573, Japan

    • Shinji Kuroda
    • , Nozomi Nishizawa
    •  & Kôki Takita
  2. Advanced Materials and Nanomaterials Laboratories, National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan

    • Masanori Mitome
    •  & Yoshio Bando
  3. Faculty of Physics, Warsaw University of Technology, Koszykowa 75, PL 00-662 Warszawa, Poland

    • Krzysztof Osuch
  4. Department of Physics, University of South Africa, PO Box 392, Pretoria 0003, South Africa

    • Krzysztof Osuch
  5. Laboratory for Cryogenic and Spintronic Research, Institute of Physics, Polish Academy of Sciences, and ERATO Semiconductor Spintronics JST Project, al. Lotników 32/46, PL 02-668 Warszawa, Poland

    • Tomasz Dietl
  6. Institute of Theoretical Physics, Warsaw University, PL 00-681 Warszawa, Poland

    • Tomasz Dietl

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The authors declare no competing financial interests.

Corresponding authors

Correspondence to Shinji Kuroda or Tomasz Dietl.

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https://doi.org/10.1038/nmat1910

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