Effects of Coulomb interaction on the electronic structure and lattice dynamics of the Mott insulator Fe2SiO4 spinel

Mariana Derzsi, Przemysław Piekarz, Paweł T. Jochym, Jan Łażewski, Małgorzata Sternik, Andrzej M. Oleś, and Krzysztof Parlinski
Phys. Rev. B 79, 205105 – Published 8 May 2009

Abstract

Using the ab initio density-functional generalized gradient approximation with varying on-site Coulomb interaction U, the electronic and crystal structures of Fe2SiO4 spinel were optimized at high pressure. It was found that the ground state changes from the metallic ferromagnetic state at U=0 into the antiferromagnetic state, stable in the regime of Mott insulating state for U>2eV. We found that Fe2SiO4 spinel is an antiferromagnetic Mott insulator at the realistic value of U4.5eV, with a distinct gap which opens in the minority-Fe(3d) states. We point out that the low value of the Néel temperature TN12K follows from the geometrical frustration of magnetic interactions, while the exchange constant J1.7meV estimated from the energies of ordered magnetic phases gives a rather high value of the Curie-Weiss temperature θCW340K. The phonon-dispersion curves and phonon density of states were derived for both the metallic and insulating antiferromagnetic phase of Fe2SiO4 spinel, and significant changes of energy and dispersion of certain phonon modes, particularly with large Fe character, caused by local electron correlations were detected and analyzed. We point out some similarities with the electronic and dynamical properties of magnetite.

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  • Received 30 January 2009

DOI:https://doi.org/10.1103/PhysRevB.79.205105

©2009 American Physical Society

Authors & Affiliations

Mariana Derzsi*

  • Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, PL-31342 Kraków, Poland
  • and Department of Theoretical Chemistry, Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava, Slovakia

Przemysław Piekarz, Paweł T. Jochym, Jan Łażewski, Małgorzata Sternik, Andrzej M. Oleś, and Krzysztof Parlinski

  • Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, PL-31342 Kraków, Poland

  • *Present address: Interdisciplinary Centre for Mathematical and Computational Modelling (ICM), University of Warsaw, Pawinskiego 5A, PL-02106 Warsaw, Poland.

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Vol. 79, Iss. 20 — 15 May 2009

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