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Comparison of Exchange Interactions in II-VI, III-V, and I-II-V Dilute Magnetic Semiconductors: Density Functional Approach

100%
Mašek J., Kudrnovský J., Máca F., Jungwirth T.
Acta Physica Polonica A
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2006
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vol. 110
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issue 2
249-254
EN
We use the coherent potential method based on the density-functional theory to compare the electronic structures and magnetic characteristics of mixed crystals (Ga,Mn)As, (Zn,Mn)Se, and Li(Zn,Mn)As. We show that, with the same degree of doping, the magnetic behavior of these materials is very similar, reflecting the similarity of their electronic structures. In particular, the superexchange in (Ga,Mn)As is as strong as in (Zn,Mn)Se and the ferromagnetic coupling in all these dilute magnetic semiconductors becomes dominant only at sufficient concentration of the holes. Remarkably, we find that ferromagnetic state appears not only in p-type, but also in n-type materials at a comparable level of doping. Although obtaining strongly n-type doped III-V dilute magnetic semiconductors is improbable, Li(Zn,Mn)As seems to be a promising candidate for a ferromagnetic n-type semiconductor.
2
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Interstitial Mn in (Ga,Mn)As: Hybridization with Conduction Band and Electron Mediated Exchange Coupling

100%
Mašek J., Kudrnovský J., Máca F., Jungwirth T.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
215-219
EN
We investigate theoretically the possibility of n-type DMS based on III-V materials with Mn impurities in interstitial instead of substitutional positions, and discuss some situations when this can happen. We show that the d-states at interstitial Mn atoms in (Ga,Mn)As hybridize with both valence and conduction bands. The hybridization is strong enough to establish an indirect ferromagnetic coupling of the Mn magnetic moments mediated either by holes or by conduction electrons. Moreover, the Curie temperatures estimated within the mean-field theory are comparable with T_c obtained for conventional materials with the same concentration of Mn_{Ga}.
3
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Interlayer Exchange Coupling: Effect of Alloying

88%
Kudrnovský J., Drchal V., Turek I., Šob M., Weinberger P.
Acta Physica Polonica A
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1997
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vol. 91
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issue 1
15-25
EN
The effect of disorder in magnetic layers, in the spacer, and at interfaces between them on periods, amplitudes, and phases of oscillations of interlayer exchange coupling in magnetic multilayers is studied theoretically on the ab initio level. We employ the spin-polarized surface Green function technique within the tight-binding linear muffin-tin orbital method and the Lloyd formulation of the interlayer exchange coupling. The coherent potential approximation is used to describe the effect of alloying. The calculations are significantly simplified by employing the vertex-cancellation theorem. Numerical results illustrating the effect of various kinds of disorder in the system on the properties of the interlayer exchange coupling are presented.
4
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Compositional Dependence of the Formation Energies of Substitutional and Interstitial Mn in Partially Compensated (Ga,Mn)As

88%
Mašek J., Turek I., Kudrnovský J., Máca F., Drchal V.
Acta Physica Polonica A
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2004
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vol. 105
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issue 6
637-644
EN
We use the density-functional theory to calculate the total energy of mixed crystals (Ga,Mn)As with a small concentration of various donors. We find that the formation energy of Mn depends strongly on the partial concentrations of Mn in the substitutional and interstitial positions, and on the concentration of other dopants. The composition dependence of the formation energies represents an effective feedback mechanism, resulting in the self-compensation property of (Ga,Mn)As. We show that the partial concentrations of both substitutional and interstitial Mn increase proportionally to the total concentration of Mn.
5
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Correlated Doping in Semiconductors: the Role of Donors in III-V Diluted Magnetic Semiconductors

88%
Mašek J., Turek I., Drchal V., Kudrnovský J., Máca F.
Acta Physica Polonica A
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2002
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vol. 102
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issue 4-5
673-678
EN
We investigate the compositional dependence of the total energy of the mixed crystals (Ga,Mn)As co-doped with As, Sn, and Zn. Using the ab initio linear muffin-tin orbital coherent potential approximation method we find a correlation between the incorporation of acceptors (Mn, Zn) and donors (Sn, antisite As). In particular, the formation energy of As_{Ga} is reduced by approximately 0.1 eV in the presence of Mn, and vice versa. This leads to the self-compensating behavior of (Ga,Mn)As.
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