Condutância em nanofios magnéticos diluídos
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2010
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Universidade Federal de Goiás
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We investigate core-shell nanowires of diluted magnetic semiconductors (DMS) with
remote n-type modulation doping. The incorporation of Mn2 ions acting as spin 5/2 impurities
in the core region of the wire gives rise to a strong s-d exchange coupling between electrons
in the wire and those of the d levels of the Mn2 ions. Applying an external magnetic eld
along the axis of the wire, within the mean eld approximation, the s-d exchange generates
a spin-dependent core potential. A gate voltage is applied radially to wire, to obtain some
control over the density of the wire. Electronic strucutre of the wire was calculated within
the e?ective mass approximation, in both approximations Hartree and spin density functional
theory. We calculated the conductance of wire using the Landauer-B?uttiker formulation in the
linear response regime, which generally results in a total conductance with well-de ned plateaus
in GT = 2; 6; 10G0 (G0 = e2=h is the quanta of conductance), which occurred because in the
system investigated the rst level is twofold degenerated (spin degenerescence) and the others
are fourfold degenerated (spin degenerescence and orbital angular momentum). In the absence
of a magnetic eld we observe that when we take into account the e?ects of exchange and
correlation, the states with eigenvalues of Lz nonzero will be polarized while those with l = 0
isn't polarized. This unpolarized level with eigenvalue of Lz null suggests that, perhaps, the
0.7 anomaly (the emergence of two plateau at G = 0:7G0 and the other in G = G0) quantum
wires on existing geometry of split-gate is related to the geometry of the wire. The results for
total energy show that there are a competition between the ferromagnetic and paramagnetic
states.
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MENDES, Udson Cabra. Condutância em nanofios magnéticos diluídos. 2010. 97 f. Dissertação ( Mestrado em Fisica) - Universidade Federal de Goiás, Goiânia.