Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 34: Neue Materialien
HL 34.1: Vortrag
Samstag, 5. März 2005, 15:00–15:15, TU P-N226
Ferromagnetism in Fe-doped ZnGa2O4 semiconductor — •Tulika Maitra and Roser Valentí — Institut für Theoretische Physik, J. W. Goethe Universität, Robert-Mayer Str. 8, 60054 Frankfurt am Main, Germany
Motivated by the recent experimental observation of long range ferromagnetic order at a relatively high temperature of 200K in the Fe doped ZnGa2O4 semiconducting spinel, we propose a possible mechanism for the observed ferromagnetism in this system. We show how a double exchange model can be written down for this system and calculate the ground state phase diagram in this model for two cases, one where Fe is doped at the tetrahedral position and the other where it is doped at the octahedral position. We find that in both cases such a model can give rise to a stable ferromagnetic phase in a wide range of parameter space. The results for a single orbital are different from the degenerate two-orbital case in the limit of high Fe2+ concentration. The doubly-degenerate eg orbitals and the hopping between them play a crucial role in stabilising the ferromagnetic phase in this limit. The case when Fe is doped in both the tetrahedral and the octahedral positions is also outlined.