Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias
Autor(a) principal: | |
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Data de Publicação: | 2012 |
Tipo de documento: | Tese |
Idioma: | por |
Título da fonte: | Manancial - Repositório Digital da UFSM |
Texto Completo: | http://repositorio.ufsm.br/handle/1/3920 |
Resumo: | Granular magnetic systems can be composed by magnetic particles or clusters with size of some nanometers. These magnetic nanoparticles present different magnetic order phases, as superparamagnetic, and they can be embedded in both, metallic or insulating matrix. These systems present several phenomena such as the giant magnetoresistance (GMR), extraordinary Hall effect (EHE), tunnel magnetoresistance (TMR) and Coulomb blockade. That phenomena use to disappear when a small termal fluctuation is high enough to reverse the magnetization of the clusters leading the lost the magnetic information in a very short time range. When it occurs, the particles are in superparamagnetic phase. In order to maintain the magnetic information at high values of temperature, or even to suppress the superparamagnetic limit, many works have tried to use an antiferromagnetic matrix, to induce the increase of the energy barrier among the two easy directions of magnetization by the exchange coupling in the grain(FM)/matrix(AFM) interfaces, with the purpose of stabilizing the particles magnetization. In this work, we have produced Co granular samples embedded in SiO2/CoO insulating/antifferomagnetic matrix through a sequential deposition by magnetron sputtering, in order to study the exchange bias of Co grains laterally surrounded by CoO.Were perfomed measurements of transmission eletronic microscopy (TEM), x-ray diffraction (XRD), measures low fields thermomagnetics (ZFC-FC), to obtain answers of the structural and magnétic charater of the samples. The Exchange Bias were investigated by extraordinary Hall effect, meauresments in differents temperature values in a cooling field (FC) of 5kOe. These non conventional measurements, are carried out with field cooling and the applied external field to perfomed the loop hysteresis both with perpendicular direction to the substrate. The effective anistropy, changes the magnitude up to three ordes of magnitude for different thicknesses of CoO in the limit T!0. On the other hand, the HEB linearily decreases, and goes to zero at a certain temperature. This temperature, is approximately, equal to that where the split of ZFC-FC curves occurs. This split is associated with the CoO blocking temperature, i.e. the ordering temperature of CoO. These results are reported from the finite size effect present in thin films. For the specific case of CoO, these effects lead to a nonzero net magnetization coming from uncompensed moments present on the surface that, in some cases, are responsible for the magnetic coupling governed by a local disorder and frustration, a spin-glass-like behavior. The extraodinary Hall effect and giant magnetoresistance were study of thin Fe-rich amorphous films and Fe-rich/Cu multilayers. Were investigated and compared the extraordinary Hall effect in these two types of samples and discussed it in terms of thickness and sample structure. The thicker films exhibited a strong in-plane magnetic anisotropy, and by decreasing film thickness both saturated Hall resistivity and Hall sensitivity increase. Electrical conductance increases and Hall resistivity decreases when the films are sandwiched with Cu. |
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Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange biasExtraordinary hall effect in SiO2/Co/CoO granular multilayers whith exchange-biasAntiferromagnétismoEfeito hall extraordinário (EHE)Exchange biasAntiferromagnetismExtraordinary hall effect (EHE)CNPQ::CIENCIAS EXATAS E DA TERRA::FISICAGranular magnetic systems can be composed by magnetic particles or clusters with size of some nanometers. These magnetic nanoparticles present different magnetic order phases, as superparamagnetic, and they can be embedded in both, metallic or insulating matrix. These systems present several phenomena such as the giant magnetoresistance (GMR), extraordinary Hall effect (EHE), tunnel magnetoresistance (TMR) and Coulomb blockade. That phenomena use to disappear when a small termal fluctuation is high enough to reverse the magnetization of the clusters leading the lost the magnetic information in a very short time range. When it occurs, the particles are in superparamagnetic phase. In order to maintain the magnetic information at high values of temperature, or even to suppress the superparamagnetic limit, many works have tried to use an antiferromagnetic matrix, to induce the increase of the energy barrier among the two easy directions of magnetization by the exchange coupling in the grain(FM)/matrix(AFM) interfaces, with the purpose of stabilizing the particles magnetization. In this work, we have produced Co granular samples embedded in SiO2/CoO insulating/antifferomagnetic matrix through a sequential deposition by magnetron sputtering, in order to study the exchange bias of Co grains laterally surrounded by CoO.Were perfomed measurements of transmission eletronic microscopy (TEM), x-ray diffraction (XRD), measures low fields thermomagnetics (ZFC-FC), to obtain answers of the structural and magnétic charater of the samples. The Exchange Bias were investigated by extraordinary Hall effect, meauresments in differents temperature values in a cooling field (FC) of 5kOe. These non conventional measurements, are carried out with field cooling and the applied external field to perfomed the loop hysteresis both with perpendicular direction to the substrate. The effective anistropy, changes the magnitude up to three ordes of magnitude for different thicknesses of CoO in the limit T!0. On the other hand, the HEB linearily decreases, and goes to zero at a certain temperature. This temperature, is approximately, equal to that where the split of ZFC-FC curves occurs. This split is associated with the CoO blocking temperature, i.e. the ordering temperature of CoO. These results are reported from the finite size effect present in thin films. For the specific case of CoO, these effects lead to a nonzero net magnetization coming from uncompensed moments present on the surface that, in some cases, are responsible for the magnetic coupling governed by a local disorder and frustration, a spin-glass-like behavior. The extraodinary Hall effect and giant magnetoresistance were study of thin Fe-rich amorphous films and Fe-rich/Cu multilayers. Were investigated and compared the extraordinary Hall effect in these two types of samples and discussed it in terms of thickness and sample structure. The thicker films exhibited a strong in-plane magnetic anisotropy, and by decreasing film thickness both saturated Hall resistivity and Hall sensitivity increase. Electrical conductance increases and Hall resistivity decreases when the films are sandwiched with Cu.Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorSistemas granulares magnéticos podem ser formados por grãos ou aglomerados magnéticos cujo tamanho é de alguns nanômetros. Estes grãos magnéticos apresentam diferentes fases de ordenamento magnético, como o superparamagnetismo, e podem estar envolvidos tanto por matrizes metálicas como matrizes isolantes. Estes sistemas possuem uma riqueza de fenômenos, como a magnetorresitência gigante (GMR), Efeito Hall Extraordinário (EHE), magnetorresistência túnel (TMR), bloqueio de coulomb entre outros. Estes fenômenos muitas vezes desaparecem quando à energia térmica for suficiente para inverter a magnetização dos grãos, levando-os a perder informação magnética num intervalo de tempo muito curto. Quando isto ocorre dizemos que os grãos estão na fase superparamagnética. Para reter a informação magnética a temperatura ambiente, ou até mesmo suprimir o superparamagnetismo, tem-se tentado o uso de uma matriz antiferromagnética (AFM) onde os grãos ficam imersos, e o acoplamento de troca na interface grão (FM)/matriz (AFM) pode induzir um aumento na barreira de energia entre as duas direções de fácil magnetização e com isso estabilizar a magnetização dos grãos. Neste trabalho foram produzidas amostras granulares de Co imersos em matriz isolante/antiferromagnética de SiO2/CoO pela deposição alternada do metal e dos isolantes por magnetron sputtering , com a finalidade de estudar a evolução do exchange bias entre os grãos de Co que estão lateralmente envolvidos por CoO. Foram realizadas medidas de Microscopia Eletrônica de Transmissão (TEM), Difração de raios-X (XRD), medidas termomagnéticas a baixos campos (ZFC-FC), para obter respostas quanto ao caráter estrutural e magnético das amostras. O Exchange bias foi investigado por efeito Hall extraordinário, medidas à diferentes temperaturas sob um campo de resfriamento (FC) de 5kOe. Estas medidas, diferente do convencional, são realizadas com o campo de resfriamento e o campo externo aplicado para realizar a curva de magnetização ambas na direção perpendicular ao substrato. A anisotropia efetiva, varia, na sua magnitude, até três ordens de grandeza para diferentes espessuras de CoO para o limite T !0. Por outro lado, o HEB decresce linearmente, até ir à zero numa dada temperatura. Esta temperatura onde extingue-se o HEB é, aproxiamdamente, a mesma onde ocorre à separação das curvas ZFC-FC. Esta separação nas curvas está associado com a temperatura de bloqueio de CoO, ou seja, temperatura de ordenamento dos grãos de CoO responsáveis pelo acoplamento direto com os grãos de Co. Estes resultados reportados são oriúndos dos efeitos de tamanho de grão, presentes em filmes muitos finos. Para o caso específico do CoO, estes efeitos levam há presença de uma magnetização diferente de zero oriúndos dos momentos não compensados presentes na superfície que, para alguns casos, são responsáveis pelo acoplamento magnético governado por uma desordem local e frustação, um compotamento do tipo spin-glass-like . Efeito Hall extraordinário e magnetorresistência gigante foram estudados em filmes finos amorfos de FINEMET e multicamdas FINEMET/Cu. Foi investigado e comparado o efetio Hall nos dois tipos de amostras, e discutido em termos da espessura e estrutura da amostra. Para os filmes mais espessos foi observado uma forte anisotropia no plano do filme, por outro lado, quando a espessura diminui ambos, a resistividade Hall satura e a sensibilidade Hall aumenta considerável. A condutividade elétrica aumenta e a resistividade Hall diminui para as multicamadas FINEMET/Cu.Universidade Federal de Santa MariaBRFísicaUFSMPrograma de Pós-Graduação em FísicaDorneles, Lucio Strazzaboscohttp://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4795059E0Sommer, Rubem Luishttp://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4785875E6Denardin, Juliano Casagrandehttp://lattes.cnpq.br/5425237044575885Geshev, Julian Penkovhttp://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4796188E3Gomes, Matheus Gamino2017-05-092017-05-092012-07-27info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisapplication/pdfapplication/pdfGOMES, Matheus Gamino. Extraordinary hall effect in SiO2/Co/CoO granular multilayers whith exchange-bias. 2012. 102 f. Tese (Doutorado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2012.http://repositorio.ufsm.br/handle/1/3920porinfo:eu-repo/semantics/openAccessreponame:Manancial - Repositório Digital da UFSMinstname:Universidade Federal de Santa Maria (UFSM)instacron:UFSM2022-07-01T13:54:30Zoai:repositorio.ufsm.br:1/3920Biblioteca Digital de Teses e Dissertaçõeshttps://repositorio.ufsm.br/ONGhttps://repositorio.ufsm.br/oai/requestatendimento.sib@ufsm.br||tedebc@gmail.comopendoar:2022-07-01T13:54:30Manancial - Repositório Digital da UFSM - Universidade Federal de Santa Maria (UFSM)false |
dc.title.none.fl_str_mv |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias Extraordinary hall effect in SiO2/Co/CoO granular multilayers whith exchange-bias |
title |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias |
spellingShingle |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias Gomes, Matheus Gamino Antiferromagnétismo Efeito hall extraordinário (EHE) Exchange bias Antiferromagnetism Extraordinary hall effect (EHE) CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
title_short |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias |
title_full |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias |
title_fullStr |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias |
title_full_unstemmed |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias |
title_sort |
Efeito hall extraordinário em multicamadas granulares de SiO2/Co/CoO com exchange bias |
author |
Gomes, Matheus Gamino |
author_facet |
Gomes, Matheus Gamino |
author_role |
author |
dc.contributor.none.fl_str_mv |
Dorneles, Lucio Strazzabosco http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4795059E0 Sommer, Rubem Luis http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4785875E6 Denardin, Juliano Casagrande http://lattes.cnpq.br/5425237044575885 Geshev, Julian Penkov http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4796188E3 |
dc.contributor.author.fl_str_mv |
Gomes, Matheus Gamino |
dc.subject.por.fl_str_mv |
Antiferromagnétismo Efeito hall extraordinário (EHE) Exchange bias Antiferromagnetism Extraordinary hall effect (EHE) CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
topic |
Antiferromagnétismo Efeito hall extraordinário (EHE) Exchange bias Antiferromagnetism Extraordinary hall effect (EHE) CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
description |
Granular magnetic systems can be composed by magnetic particles or clusters with size of some nanometers. These magnetic nanoparticles present different magnetic order phases, as superparamagnetic, and they can be embedded in both, metallic or insulating matrix. These systems present several phenomena such as the giant magnetoresistance (GMR), extraordinary Hall effect (EHE), tunnel magnetoresistance (TMR) and Coulomb blockade. That phenomena use to disappear when a small termal fluctuation is high enough to reverse the magnetization of the clusters leading the lost the magnetic information in a very short time range. When it occurs, the particles are in superparamagnetic phase. In order to maintain the magnetic information at high values of temperature, or even to suppress the superparamagnetic limit, many works have tried to use an antiferromagnetic matrix, to induce the increase of the energy barrier among the two easy directions of magnetization by the exchange coupling in the grain(FM)/matrix(AFM) interfaces, with the purpose of stabilizing the particles magnetization. In this work, we have produced Co granular samples embedded in SiO2/CoO insulating/antifferomagnetic matrix through a sequential deposition by magnetron sputtering, in order to study the exchange bias of Co grains laterally surrounded by CoO.Were perfomed measurements of transmission eletronic microscopy (TEM), x-ray diffraction (XRD), measures low fields thermomagnetics (ZFC-FC), to obtain answers of the structural and magnétic charater of the samples. The Exchange Bias were investigated by extraordinary Hall effect, meauresments in differents temperature values in a cooling field (FC) of 5kOe. These non conventional measurements, are carried out with field cooling and the applied external field to perfomed the loop hysteresis both with perpendicular direction to the substrate. The effective anistropy, changes the magnitude up to three ordes of magnitude for different thicknesses of CoO in the limit T!0. On the other hand, the HEB linearily decreases, and goes to zero at a certain temperature. This temperature, is approximately, equal to that where the split of ZFC-FC curves occurs. This split is associated with the CoO blocking temperature, i.e. the ordering temperature of CoO. These results are reported from the finite size effect present in thin films. For the specific case of CoO, these effects lead to a nonzero net magnetization coming from uncompensed moments present on the surface that, in some cases, are responsible for the magnetic coupling governed by a local disorder and frustration, a spin-glass-like behavior. The extraodinary Hall effect and giant magnetoresistance were study of thin Fe-rich amorphous films and Fe-rich/Cu multilayers. Were investigated and compared the extraordinary Hall effect in these two types of samples and discussed it in terms of thickness and sample structure. The thicker films exhibited a strong in-plane magnetic anisotropy, and by decreasing film thickness both saturated Hall resistivity and Hall sensitivity increase. Electrical conductance increases and Hall resistivity decreases when the films are sandwiched with Cu. |
publishDate |
2012 |
dc.date.none.fl_str_mv |
2012-07-27 2017-05-09 2017-05-09 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
GOMES, Matheus Gamino. Extraordinary hall effect in SiO2/Co/CoO granular multilayers whith exchange-bias. 2012. 102 f. Tese (Doutorado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/3920 |
identifier_str_mv |
GOMES, Matheus Gamino. Extraordinary hall effect in SiO2/Co/CoO granular multilayers whith exchange-bias. 2012. 102 f. Tese (Doutorado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2012. |
url |
http://repositorio.ufsm.br/handle/1/3920 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf application/pdf |
dc.publisher.none.fl_str_mv |
Universidade Federal de Santa Maria BR Física UFSM Programa de Pós-Graduação em Física |
publisher.none.fl_str_mv |
Universidade Federal de Santa Maria BR Física UFSM Programa de Pós-Graduação em Física |
dc.source.none.fl_str_mv |
reponame:Manancial - Repositório Digital da UFSM instname:Universidade Federal de Santa Maria (UFSM) instacron:UFSM |
instname_str |
Universidade Federal de Santa Maria (UFSM) |
instacron_str |
UFSM |
institution |
UFSM |
reponame_str |
Manancial - Repositório Digital da UFSM |
collection |
Manancial - Repositório Digital da UFSM |
repository.name.fl_str_mv |
Manancial - Repositório Digital da UFSM - Universidade Federal de Santa Maria (UFSM) |
repository.mail.fl_str_mv |
atendimento.sib@ufsm.br||tedebc@gmail.com |
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1805922172336603136 |