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MA: Magnetismus
MA 17: Spinstrukturen /Magn. Phasenüberg
änge
MA 17.1: Vortrag
Mittwoch, 10. März 2004, 17:45–18:00, H10
The half-metal to metal transition in magnetite - a density-functional-theory study — •Martin Friák1, Arno Schindlmayr1,2, and Matthias Scheffler1 — 1Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin. — 2Institut für Festkörperforschung, Forschungszentrum Jülich.
We analyze the influence of various external conditions (uniaxial and biaxial stress, pressure, substitutional dopants) that induce a half-metal to metal transition leading to a loss of the material’s desirable half-metallic properties. Total energies, electronic structure, and magnetic moments are calculated by DFT using the full-potential linearized augmented plane-wave method. Results obtained within the generalized gradient approximation (GGA) show excellent agreement with experimental findings. In response to uniaxial, biaxial or triaxial pressure, a half-metal to metal transition occurs, which shifts the Fermi energy from the gap of the majority-spin electrons under the top of the valence band so that both spin channels become metallic. We also performed a detailed total-energy analysis of five different structural and spin configurations simulating the substitution Fe2.5X0.5O4 (X = Mn, Co, Ni). The lowest-energy configurations are in good agreement with experimental observations. For Mn substitution we find a purely metallic character, qualitatively similar to the stress-induced transition in pure magnetite.