Physics – Condensed Matter – Other Condensed Matter
Scientific paper
2004-09-12
Physics
Condensed Matter
Other Condensed Matter
4 pages (5 figures); To appear in Phys. Rev. Lett
Scientific paper
10.1103/PhysRevLett.93.177201
Ferromagnetism in Mn-doped GaAs, the prototypical dilute magnetic semiconductor, has so far been attributed to hole mediated RKKY-type interactions. First-principles calculations reveal a strong direction dependence of the ferromagnetic (FM) stabilization energy of two magnetic ions, a dependence that cannot be explained within RKKY. In the limit of host-like hole (engineered here by an GGA+U approach with large U) where the RKKY model is applicable, we find that the exchange energies are strongly reduced, suggesting that this limit cannot explain the observed ferromagnetism. The dominant contribution stabilizing the FM state is found to be maximal for <110>-oriented pairs and minimal for <100> oriented pairs, providing an alternate explanation for magnetism in such materials in terms of energy lowering due to p-d hopping interactions, and offering a new design degree of freedom to enhance FM.
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Mahadevan Priya
Sarma Debojit
Zunger Alex
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