Distortions in charge-ordered LuFe$_2$O$_4$

ORAL

Abstract

Experimental evidence\footnote{Nature {\bf 436}, 1136 (2005)} suggests that LuFe$_2$O$_4$ develops ferroelectricity via a novel charge-ordering mechanism in which the Fe sites (of average valence 2.5) disproportionate into Fe$^{2+}$ and Fe$^{3+}$ sublattices in such a way as to break inversion symmetry. However, the precise nature of the charge and magnetic order, and the structural distortions that accompany them, remain poorly understood. With this motivation, we have undertaken a first-principles study of LuFe$_2$O$_4$ using DFT-based methods (especially LDA+U). We search for the ground state consistent with a variety of supercell choices and symmetry constraints, and thereby investigate whether the system is unstable to several possible charge and spin orderings. Despite the limitations of a DFT-based approach, it is argued that the results provide useful guidance in the quest to develop an understanding of the novel form of ferroelectricity displayed by this material.

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Authors

  • Takeshi Nishimatsu

  • David Vanderbilt

    Rutgers University

  • Karin M. Rabe

    Rutgers University, Department of Physics and Astronomy, Rutgers the State University of New Jersey, Piscataway, NJ 08854, USA, Rutgers, The State University of New Jersey

  • Y. Horibe

    Dept. of Physics and Astronomy, Rutgers University

  • SangWook Cheong

    Department of Physics \& Astronomy, Rutgers University, Piscataway, New Jersey 08854, Physics Department, Rutgers University, Rutgers University, Dept. of Physics and Astronomy, Rutgers University, Rutgers Center for Emergent Materials, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, Department of Physics, Rutgers, Rutgers Univ.

  • Claude Ederer

    Columbia University