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Ferroelectricity from iron valence ordering in the charge-frustrated system LuFe2O4


Ferroelectric materials are widely used in modern electric devices such as memory elements, filtering devices and high-performance insulators. Ferroelectric crystals have a spontaneous electric polarization arising from the coherent arrangement of electric dipoles1 (specifically, a polar displacement of anions and cations). First-principles calculations2,3 and electron density analysis4 of ferroelectric materials have revealed that the covalent bond between the anions and cations, or the orbital hybridization of electrons on both ions, plays a key role in establishing the dipolar arrangement. However, an alternative model—electronic ferroelectricity5—has been proposed in which the electric dipole depends on electron correlations, rather than the covalency. This would offer the attractive possibility of ferroelectric materials that could be controlled by the charge, spin and orbital degrees of freedom of the electron. Here we report experimental evidence for ferroelectricity arising from electron correlations in the triangular mixed valence oxide, LuFe2O4. Using resonant X-ray scattering measurements, we determine the ordering of the Fe2+ and Fe3+ ions. They form a superstructure that supports an electric polarization consisting of distributed electrons of polar symmetry. The polar ordering arises from the repulsive property of electrons—electron correlations—acting on a frustrated geometry.

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Figure 1: The charge-ordering model of the double iron layer in RFe2O4.
Figure 2: X-ray energy dependence of the superlattice reflection (1/3, 1/3, 5.5) of a LuFe 2 O 4 single crystal.
Figure 3: Temperature variation of the electric polarization of LuFe2O4.
Figure 4: The a.c. dielectric dispersion in an LuFe 2 O 4 polycrystalline sample.


  1. Kittel, C. Introduction to Solid State Physics (Wiley, New York, 1995)

    MATH  Google Scholar 

  2. Cohen, R. E. Origin of ferroelectricity in perovskite oxides. Nature 358, 136–138 (1992)

    Article  ADS  CAS  Google Scholar 

  3. Sághi-Szabó, G., Cohen, R. E. & Krakauer, H. First-principles study of piezoelectricity in PbTiO3 . Phys. Rev. Lett. 80, 4321–4324 (1998)

    Article  ADS  Google Scholar 

  4. Kuroiwa, Y. et al. Evidence for Pb-O covalency in tetragonal PbTiO3 . Phys. Rev. Lett. 87, 217601 (2001)

    Article  ADS  CAS  Google Scholar 

  5. Portengen, T., Östreich, Th. & Sham, L. J. Theory of electronic ferroelectricity. Phys. Rev. B 54, 17452–17463 (1996)

    Article  ADS  CAS  Google Scholar 

  6. Kimizuka, N., Muromachi, E. & Siratori, K. in Handbook on the Physics and Chemistry of Rare Earths Vol. 13 (eds Gschneidner, K. A. Jr & Eyring, L.) 283–384 (Elsevier Science, Amsterdam, 1990)

    Google Scholar 

  7. Yamada, Y., Nohdo, S. & Ikeda, N. Incommensurate charge ordering in charge-frustrated LuFe2O4 system. J. Phys. Soc. Jpn 66, 3733–3736 (1997)

    Article  ADS  CAS  Google Scholar 

  8. Mekata, M. & Adachi, K. Magnetic structure of CsCoCl3 . J. Phys. Soc. Jpn 44, 806–812 (1978)

    Article  ADS  CAS  Google Scholar 

  9. Funahashi, S. et al. Two-dimensional spin correlation in YFe2O4 . J. Phys. Soc. Jpn 53, 2688–2696 (1984)

    Article  ADS  CAS  Google Scholar 

  10. Materlik, G., Sparks, C. J. & Fischer, K. Resonant Anomalous X-Ray Scattering (North-Holland, Amsterdam, 1994)

    Google Scholar 

  11. Sasaki, S. Fe2+ and Fe3+ ions distinguishable by X-ray anomalous scattering: method and its application to magnetite. Rev. Sci. Instrum. 66, 1573–1576 (1995)

    Article  ADS  CAS  Google Scholar 

  12. Murakami, Y. et al. Direct observation of charge and orbital ordering in La0.5Sr1.5MnO4 . Phys. Rev. Lett. 80, 1932–1935 (1998)

    Article  ADS  CAS  Google Scholar 

  13. Ikeda, N. et al. Charge frustration and dielectric dispersion in LuFe2O4 . J. Phys. Soc. Jpn 69, 1526–1532 (2000)

    Article  ADS  CAS  Google Scholar 

  14. Hill, A. N. Why are there so few magnetic ferroelectrics? J. Phys. Chem. B 104, 6694–6709 (2000)

    Article  CAS  Google Scholar 

  15. Ikeda, N., Kohn, K., Kito, H., Akimitsu, J. & Siratori, K. Dielectric relaxation and hopping of electrons in ErFe2O4 . J. Phys. Soc. Jpn 63, 4556–4564 (1994)

    Article  ADS  CAS  Google Scholar 

  16. Tanaka, M., Siratori, K. & Kimizuka, N. Mössbauer study in RFe2O4 . J. Phys. Soc. Jpn 53, 760–772 (1984)

    Article  ADS  CAS  Google Scholar 

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The authors express their gratitude to H. Suematsu and M. Takata for discussions.

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Correspondence to Naoshi Ikeda.

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Ikeda, N., Ohsumi, H., Ohwada, K. et al. Ferroelectricity from iron valence ordering in the charge-frustrated system LuFe2O4. Nature 436, 1136–1138 (2005).

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