Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 24: Postersitzung III: Korrelierte Elektronen, ”Orbital Physics”
TT 24.43: Poster
Mittwoch, 10. März 2004, 14:30–19:00, Poster A
Comparison of LSDA+U calculations and photo emission data of Fe3O4 — •David Schrupp1, Ivan Leonov1, Alexander Yaresko2, Shigemasa Suga3, Vladimir Anisimov4, and Ralph Claessen1 — 1Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany — 2Max Planck Institute for Physics of Complex Systems, 01187 Dresden, Germany — 3Department of Material Physics, Osaka University, Osaka 560-8531, Japan — 4Institute of Metal Physics, Ekaterinburg GSP-170, Russia
Magnetite, undergoes a first-order phase transition, reflected by an increase of electrical resistivity by two orders of magnitude, called the Verwey transition. Although known for a long time the Verwey transition is currently a matter of intensive debate questioning fundamental issues such as the charge ordering of Fe2+ ions which is widely believed to be the driving mechanism of the Verwey transition.
The LSDA+U calculations based on new structure refinements in the low temperature phase of magnetite result in a charge and orbitally ordered insulator. The self-consistent solution corresponding to charge order does not satisfy the widely-accepted Anderson condition of minimum electrostatic repulsion, but agrees with photoemission spectra, taken below the Verwey transition temperature.
These spectra where obtained by using polished, sputtered, annealed and post-oxidized single crystals. The correct stoichiometry and long-range order of the thus prepared surfaces were proven by LEED, STM, and XPS. The samples were measured with high energy photoemission (ℏω≈700 eV), which means an enhanced information depth.