Condutância em nanofios magnéticos diluídos
| Autor(a) principal: | |
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| Data de Publicação: | 2010 |
| Tipo de documento: | Dissertação |
| Idioma: | por |
| Título da fonte: | Repositório Institucional da UFG |
| Texto Completo: | http://repositorio.bc.ufg.br/tede/handle/tde/2888 |
Resumo: | 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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Avelar, Ardiley Torreshttp://lattes.cnpq.br/5732286631137637Leão, Salvino de Araújohttp://lattes.cnpq.br/2549501479254454Mendes, Udson Cabra2014-08-06T12:19:22Z2010MENDES, Udson Cabra. Condutância em nanofios magnéticos diluídos. 2010. 97 f. Dissertação ( Mestrado em Fisica) - Universidade Federal de Goiás, Goiânia.http://repositorio.bc.ufg.br/tede/handle/tde/2888We 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.Investigamos nano fios de semicondutores magnéticos dilu??dos (DMSs - Diluted Magnetic Semiconductors) do tipo caroço-casca com dopagem remota tipo-n. A incorporação dos íons de Mn+2, que atuam como impurezas de spin 5/2 no caroço do fi o, faz surgir um forte acoplamento de trocas dentre os eletrons do fio e aqueles dos níveis d do íon Mn+2. Com a aplicação de um campo magnético externo ao longo do eixo do fi o, na aproximação de campo médio, a interação de troca s-d gera um potencial dependente do spin na região do caroço do fi o. Um potencial de gate é aplicado radialmente ao nanofi o, para obtermos um certo controle sobre a densidade eletrônica do fi o. Calculamos a estrutura eletrônica do nanofi o de DMSs usando o modelo da massa efetiva, tanto na aproximação de Hartree quanto na teoria do funcional da densidade dependente de spin (SDFT - Spin Density Functional Theory). Calculamos a condutância do nano fio usando a formulação de Landauer-B?uttiker no regime de resposta linear, o que de modo geral, resultou numa condutância total com platôs bem de finidos em GT = 2; 6; 10G0 (G0 = e2=h ?e o quanta de condutância), o que ocorreu porque no sistema investigado a primeira subbanda ?e duplamente degenerada (degenerescência de spin) e as outras duas são quadruplamente degenerada (degenerescência de spin e de momento angular orbital). Na ausência de um campo magnético observamos que ao levarmos em conta os efeitos de troca e correlação, os estados que possuem autovalor de Lz diferente de zero se polarizam enquanto que os que possuem l = 0 não se polarizam. Essa não-polarização do nível com autovalor de Lz nulo sugere que, talvez, a anomalia 0,7 (o surgimento de dois platôs um em G = 0; 7G0 e outro em G = G0) existente em os quânticos com geometria de split-gate esteja relacionada com a geometria do o. Os resultados obtidos para a energia total mostram que há uma competição entre os estados ferromagnético e paramagnéticos.Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-08-06T12:19:22Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) udson cabral.pdf: 2045459 bytes, checksum: 0c5126468995368f097978ee97cb41f5 (MD5)Made available in DSpace on 2014-08-06T12:19:22Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) udson cabral.pdf: 2045459 bytes, checksum: 0c5126468995368f097978ee97cb41f5 (MD5) Previous issue date: 2010Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESConselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPqapplication/pdfhttp://repositorio.bc.ufg.br/tede/retrieve/6056/udson%20cabral.pdf.jpgporUniversidade Federal de GoiásPrograma de Pós-graduação em Fisica (IF)UFGBrasilInstituto de Física - IF (RG)[1] S. A. Wolf, D. D. Awschalom, R. A. Buhrman, J. M. Daughton, S. Von Moln ́ar, M. L. Roukes, A. Y. Chtchelkanova, e D. M. Treger. Spintronics: A Spin-Based Electronics Vision for the Future. Science, 294, 1488, 2001. [2] D. D. Awschalom e M. E. Flatt ́e. Challenges for semiconductor spintronics. Nature Physics, 3, 153–159, 2007. [3] Y. K. Kato, R. C. Myers, A. C. Gossard, e D. D. Awschalom. Observation of the Spin Hall Effect in Semiconductors. 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| dc.title.por.fl_str_mv |
Condutância em nanofios magnéticos diluídos |
| dc.title.alternative.por.fl_str_mv |
Conductancia in nanowires of magnetic diluited |
| title |
Condutância em nanofios magnéticos diluídos |
| spellingShingle |
Condutância em nanofios magnéticos diluídos Mendes, Udson Cabra Nanofios magnéticos Condutância Magnetic nanowires Conductance CIENCIAS EXATAS E DA TERRA::FISICA |
| title_short |
Condutância em nanofios magnéticos diluídos |
| title_full |
Condutância em nanofios magnéticos diluídos |
| title_fullStr |
Condutância em nanofios magnéticos diluídos |
| title_full_unstemmed |
Condutância em nanofios magnéticos diluídos |
| title_sort |
Condutância em nanofios magnéticos diluídos |
| author |
Mendes, Udson Cabra |
| author_facet |
Mendes, Udson Cabra |
| author_role |
author |
| dc.contributor.advisor1.fl_str_mv |
Avelar, Ardiley Torres |
| dc.contributor.advisor1Lattes.fl_str_mv |
http://lattes.cnpq.br/5732286631137637 |
| dc.contributor.advisor-co1.fl_str_mv |
Leão, Salvino de Araújo |
| dc.contributor.authorLattes.fl_str_mv |
http://lattes.cnpq.br/2549501479254454 |
| dc.contributor.author.fl_str_mv |
Mendes, Udson Cabra |
| contributor_str_mv |
Avelar, Ardiley Torres Leão, Salvino de Araújo |
| dc.subject.por.fl_str_mv |
Nanofios magnéticos Condutância |
| topic |
Nanofios magnéticos Condutância Magnetic nanowires Conductance CIENCIAS EXATAS E DA TERRA::FISICA |
| dc.subject.eng.fl_str_mv |
Magnetic nanowires Conductance |
| dc.subject.cnpq.fl_str_mv |
CIENCIAS EXATAS E DA TERRA::FISICA |
| description |
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. |
| publishDate |
2010 |
| dc.date.issued.fl_str_mv |
2010 |
| dc.date.accessioned.fl_str_mv |
2014-08-06T12:19:22Z |
| dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
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info:eu-repo/semantics/masterThesis |
| format |
masterThesis |
| status_str |
publishedVersion |
| dc.identifier.citation.fl_str_mv |
MENDES, Udson Cabra. Condutância em nanofios magnéticos diluídos. 2010. 97 f. Dissertação ( Mestrado em Fisica) - Universidade Federal de Goiás, Goiânia. |
| dc.identifier.uri.fl_str_mv |
http://repositorio.bc.ufg.br/tede/handle/tde/2888 |
| identifier_str_mv |
MENDES, Udson Cabra. Condutância em nanofios magnéticos diluídos. 2010. 97 f. Dissertação ( Mestrado em Fisica) - Universidade Federal de Goiás, Goiânia. |
| url |
http://repositorio.bc.ufg.br/tede/handle/tde/2888 |
| dc.language.iso.fl_str_mv |
por |
| language |
por |
| dc.relation.program.fl_str_mv |
3162138865744262028 |
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600 600 600 600 600 |
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-4029658853652049306 |
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-8327146296503745929 |
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2075167498588264571 -2555911436985713659 |
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