Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
2004-12-20
J. Phys.: Condens. Matter 17 (2005) 7417-7431
Physics
Condensed Matter
Strongly Correlated Electrons
10 pages, 9 figures, added text, J. Phys. Cond. Mat. (to appear)
Scientific paper
10.1088/0953-8984/17/46/025
Motivated by the recent experimental observation of long range ferromagnetic order at a relatively high temperature of 200K in the Fe-doped ZnGa$_2$O$_4$ semiconducting spinel, we propose a possible mechanism for the observed ferromagnetism in this system. We show, supported by band structure calculations, how a model similar to the double exchange model can be written down for this system and calculate the ground state phase diagram for the two cases where Fe is doped either at the tetrahedral position or at the octahedral position. We find that in both cases such a model can account for a stable ferromagnetic phase in a wide range of parameter space. We also argue that in the limit of high Fe$^{2+}$ concentration at the tetrahedral positions a description in terms of a two band model is essential. The two $e_g$ orbitals and the hopping between them play a crucial role in stabilizing the ferromagnetic phase in this limit. The case when Fe is doped simultaneously at both the tetrahedral and the octahedral position is also discussed.
Maitra Tulika
Valent{\'ı} Roser
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