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A Model of the Electron Transport in a Quantum Wire with Contacts

100%
Jungwirth T.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
882-886
EN
A new model of the electron transport in a quantum wire with contacts is presented. The contact between the reservoir and the quantum past of the system is assumed to be lengthwise the ideal lead. The equilibrium state of electrons in the reservoir gives the final distribution of a non-equilibrium electron system in the ideal lead. The model enables a continuous quasi-1D description of the electron transport evoked by a difference of chemical potentials as well as by a difference of temperatures of reservoirs.
2
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Magnetic and Transport Properties of (III,Mn)V Ferromagnetic Semiconductors

51%
Jungwirth T., Sinova J., MacDonald A.
Acta Physica Polonica A
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2003
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vol. 104
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issue 2
103-112
EN
The basic microscopic origins of ferromagnetism in (III,Mn)V compounds that have the highest transition temperatures appear to be well understood, and efficient computation methods have been developed which are able to model their magnetic, transport, and optical properties. We review some of the attempts over the past five years to achieve a theoretical under standing of these complex magnetic systems.
3
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Uniaxial Strain Controlling Magnetic Anisotropy in (Ga,Mn)As

51%
Zemen J., Jungwirth T., Wunderlich J., Gallagher B.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
431-435
EN
A theoretical study of magnetocrystalline anisotropy controlled by in-plane lattice symmetry distortions is presented. The uniaxial strain, only presumed by earlier studies in order to model the observed uniaxial magnetic anisotropy, has recently become an experimentally accessible parameter. We show that the lithographically induced strain can compete with intrinsic symmetry breaking, easy axes can take general in-plane directions, and anisotropy fields scale linearly with strain for typical experimental strain magnitudes. Our results are in qualitative agreement with experimental results.
4
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Comparison of Exchange Interactions in II-VI, III-V, and I-II-V Dilute Magnetic Semiconductors: Density Functional Approach

51%
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.
5
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Interstitial Mn in (Ga,Mn)As: Hybridization with Conduction Band and Electron Mediated Exchange Coupling

51%
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}.
6
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In-Plane/Tilted Magnetic-Field-Dependent Conductance of 2D Electron Systems in Asymmetric Double Quantum Wells

39%
Smrčka L., Vašek P., Jungwirth T., Makarovskii O. N., Cukr M., Jansen L.
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EN
The resistance in an asymmetric double-well structure was measured as a function of magnetic fields oriented almost parallel to the plane of the electron layer. It was shown that the shape of the magnetoresistance curves is close to the in-plane magnetic-field-dependent density of states which we obtained by self-consistent numerical calculation. The novel feature is the negative magnetoresistance observed at low magnetic fields.
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