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Room-temperature ferromagnetism in graphite driven by two-dimensional networks of point defects

Nature Physics volume 5, pages 840844 (2009) | Download Citation

Abstract

Understanding the mechanism of ferromagnetism in carbon-based materials, which contain only s and p electrons in contrast to traditional ferromagnets based on 3d or 4f electrons, is challenging. Here, we demonstrate direct evidence for ferromagnetic order locally at defect structures in highly oriented pyrolytic graphite (HOPG) with magnetic force microscopy and in bulk magnetization measurements at room temperature. Magnetic impurities have been excluded as the origin of the magnetic signal. The observed ferromagnetism has been attributed to originate from localized electron states at grain boundaries of HOPG, forming two-dimensional arrays of point defects. The theoretical value of the magnetic ordering temperature based on weak interlayer coupling and/or magnetic anisotropy is comparable to the experimental value. The unusual chemical environment of defects bonded in graphitic networks can reveal the role of the s and p electrons, creating new routes for spin transport in carbon-based materials.

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Acknowledgements

We are very grateful to R. Lavrijsen for SQUID measurements, P. H. A. Mutsaers for PIXE analysis and H. H. Brongersma for LEIS measurements. We thank B. Koopmans and H. J. M. Swagten for fruitful discussions and comments on the manuscript. This research was supported by Nanoned.

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Author notes

    • J. Červenka

    Present address: Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, CZ-162 53 Prague 6, Czech Republic

Affiliations

  1. Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands

    • J. Červenka
    •  & C. F. J. Flipse
  2. Institute of Molecules and Materials, Radboud University of Nijmegen, NL-6525 ED Nijmegen, The Netherlands

    • M. I. Katsnelson

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Contributions

J.C. carried out the experiments and wrote the paper. J.C. and C.F.J.F. designed and coordinated the experiments. M.I.K carried out the theoretical modelling. All authors discussed the results, analysed the data and commented on the manuscript.

Corresponding author

Correspondence to C. F. J. Flipse.

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https://doi.org/10.1038/nphys1399

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