Exchange interactions in III-V and group-IV diluted magnetic semiconductors

J. Kudrnovský, I. Turek, V. Drchal, F. Máca, P. Weinberger, and P. Bruno
Phys. Rev. B 69, 115208 – Published 17 March 2004
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Abstract

Effective pair exchange interactions between Mn atoms in III-V and group-IV diluted magnetic semiconductors are determined from a two-step first-principles procedure. In the first step, the self-consistent electronic structure of a system is calculated for a collinear spin structure at zero temperature with the substitutional disorder treated within the framework of the coherent-potential approximation. The effective exchange pair interactions are then obtained in a second step by mapping the total energies associated with rotations of magnetic moments onto an effective classical Heisenberg Hamiltonian using the magnetic force theorem and one-electron Green functions. The formalism is applied to Ga1xMnxAs alloys with and without As antisites, and to Ge1xMnx alloys recently studied experimentally. A detailed study of the behavior of pair exchange interactions as a function of the distance between magnetic atoms as well as a function of the concentrations of the magnetic atoms and compensating defects is presented. We have found that due to disorder and the half-metallic character of the system the pair exchange interactions are exponentially damped with increasing distance between the Mn atoms. The exchange interactions between Mn atoms are ferromagnetic for distances larger than the ones corresponding to the averaged nearest-neighbor Mn-Mn distance. The pair exchange interactions are also reduced with increasing concentrations of the Mn atoms and As antisites. As a simple application of the calculated exchange interactions we present mean-field estimates of Curie temperatures.

  • Received 26 March 2002

DOI:https://doi.org/10.1103/PhysRevB.69.115208

©2004 American Physical Society

Authors & Affiliations

J. Kudrnovský1,4,5, I. Turek2,3,4, V. Drchal1,4, F. Máca1,4, P. Weinberger4, and P. Bruno5

  • 1Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, CZ-182 21 Prague 8, Czech Republic
  • 2Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, CZ-616 62 Brno, Czech Republic
  • 3Department of Electronic Structures, Charles University, Ke Karlovu 5, CZ-121 16 Prague 2, Czech Republic
  • 4Center for Computational Materials Science, Technical University of Vienna, Getreidemarkt 9, A-1060 Vienna, Austria
  • 5Max-Planck Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany

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Vol. 69, Iss. 11 — 15 March 2004

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