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Advanced Materials

Signature of Intrinsic High-Temperature Ferromagnetism in Cobalt-Doped Zinc Oxide Nanocrystals

Authors

  • X. F. Wang,

    1. Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, P.R. China
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  • J. B. Xu,

    1. Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, P.R. China
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  • B. Zhang,

    1. Department of Physics and Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, P.R. China
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  • H. G. Yu,

    1. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, P.R. China
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  • J. Wang,

    1. Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, P.R. China
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  • X. Zhang,

    1. Department of Physics and Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, P.R. China
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  • J. G. Yu,

    1. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, P.R. China
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  • Q. Li

    1. Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, P.R. China
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  • X.F.W. and J.B.X. thank Prof. S. P. Wong and Prof. R. Zhang for stimulating discussions and Dr. W. Y. Cheung, Dr. N. Ke, and W. K. Chan for technical assistance. This work was supported in part by the Research Grants Council of Hong Kong (CERG Grant #CUHK4203/01E, Direct Grant #CUHK2 050 327, and Direct Grant #HKUST605 605) and the NSFC (Grant #20 473 059). Supporting Information is available online from Wiley InterScience or from the author.

Abstract

Nanocrystalline Zn1–xCoxO (x = 0.020, 0.056, and 0.098) powders exhibit intrinsic high-temperature ferromagnetism, as suggested by the well-defined hysteresis loops shown in the figure. The origin of this ferromagnetism is thought to be electron transfer from host Zn 4s states to unfilled dopant Co 3d states (shown in the inset to the figure), which leads to the formation of a spin-split impurity band at the Fermi level in the gap.

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