Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters
Autor(a) principal: | |
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Data de Publicação: | 2019 |
Tipo de documento: | Tese |
Idioma: | por |
Título da fonte: | Manancial - Repositório Digital da UFSM |
Texto Completo: | http://repositorio.ufsm.br/handle/1/16501 |
Resumo: | In magnetic systems, frustration - which refers to the inhability to satisfy all the interactios simultaneously - has ravealed a rich phenomenology. In particular, disorder and geometrical features are possible sources of frustration. Systems that combine these two sources generally give rise to a number of challenging problems. In the present work, we approach the interplay between geometrical frustration (GF) and bond disorder, focusing in the rich phenomenology underlying the cluster spin glass (CSG) phase stabilization. In order to deal with this problem we considered the van Hemmen and the Sherrington-Kirkpatrick cluster models, as well as cluster mean-field methods. Our studies focused on the J1-J2 square, the antiferromagnetic kagome and the checkerboard Ising lattices with intercluster disorder. In the square and kagome lattices, we studied the CSG onset at low levels of disorder in geometrically frustrated systems, which is a problem with great experimental motivation. Our results indicate that the increase in frustration (by tuning J2=J1) reduces the minimum amount of disorder needed to stabilize the CSG in the square lattice. Moreover, for the kagome lattice, we found that an infinitesimal disorder leads to a CSG ground-state. This result can be compared to the experimental findings for the Co3Mg(OH)6Cl2 compound, that is pointed out as an experimental realization of the Ising kagome antiferromagnet. Moreover, we investigate the effects of GF on the onset of reentrant transitions. In this study, we considered a model with disorder between clusters in the presence of an external longitudinal magnetic field. Our results indicate that cluster magnets are prototypes for the observation of inverse freezing. Besides, at weak disorders, we observed the onset of field-induced CSG phases, indicating that cluster antiferromagnets are also candidates for field-induced glassy phases. |
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Efeitos de frustração geométrica em antiferromagnetos desordenados com clustersEffects of geometrical frustration on disordered antiferromagnets with clustersClustersAntiferromagnetosDesordemFrustraçãoVidro de SpinAntiferromagnetsDisorderFrustrationSpin GlassCNPQ::CIENCIAS EXATAS E DA TERRA::FISICAIn magnetic systems, frustration - which refers to the inhability to satisfy all the interactios simultaneously - has ravealed a rich phenomenology. In particular, disorder and geometrical features are possible sources of frustration. Systems that combine these two sources generally give rise to a number of challenging problems. In the present work, we approach the interplay between geometrical frustration (GF) and bond disorder, focusing in the rich phenomenology underlying the cluster spin glass (CSG) phase stabilization. In order to deal with this problem we considered the van Hemmen and the Sherrington-Kirkpatrick cluster models, as well as cluster mean-field methods. Our studies focused on the J1-J2 square, the antiferromagnetic kagome and the checkerboard Ising lattices with intercluster disorder. In the square and kagome lattices, we studied the CSG onset at low levels of disorder in geometrically frustrated systems, which is a problem with great experimental motivation. Our results indicate that the increase in frustration (by tuning J2=J1) reduces the minimum amount of disorder needed to stabilize the CSG in the square lattice. Moreover, for the kagome lattice, we found that an infinitesimal disorder leads to a CSG ground-state. This result can be compared to the experimental findings for the Co3Mg(OH)6Cl2 compound, that is pointed out as an experimental realization of the Ising kagome antiferromagnet. Moreover, we investigate the effects of GF on the onset of reentrant transitions. In this study, we considered a model with disorder between clusters in the presence of an external longitudinal magnetic field. Our results indicate that cluster magnets are prototypes for the observation of inverse freezing. Besides, at weak disorders, we observed the onset of field-induced CSG phases, indicating that cluster antiferromagnets are also candidates for field-induced glassy phases.Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPqEm sistemas magnéticos, a frustração - associada à incapacidade de satisfazer todas as interações simultaneamente - tem revelado uma grande riqueza fenomenológica. Em particular, desordem e características geométricas são possíveis fontes de frustração. Sistemas que coadunam estas duas fontes geralmente dão origem a uma série de problemas desafiadores. No presente trabalho, abordamos a relação entre frustração geométrica (FG) e interações desordenadas, focando na rica fenomenologia subjacente ao aparecimento da fase vidro de spin com clusters (VSC). Dentre as técnicas consideradas estão as abordagens com clusters dos modelos de van Hemmen e de Sherrington-Kirkpatrick, bem como teorias de campo médio com clusters. Através desses métodos, investigamos modelos de spins de Ising nas redes quadrada J1-J2, kagome e checkerboard na presença de desordem intercluster. No estudo das redes quadrada e kagome, focamos no aparecimento da fase VSC em baixos níveis de desordem em sistemas frustrados, problema este com grande motivação experimental. Nossos resultados para a rede quadrada indicam que o aumento da frustração (através do ajuste da relação J2=J1) reduz a desordem mínima necessária para a estabilização da fase VSC na rede quadrada. Um resultado particularmente interessante ocorre na rede kagome, na qual uma desordem infinitesimal leva a um estado fundamental VSC. Esses resultados podem ser comparados às observações experimentais para o composto Co3Mg(OH)6Cl2, que é apontado como uma realização da rede kagome de Ising antiferromagnética. Além disso, investigamos os efeitos de FG no aparecimento de reentrâncias considerando modelos com desordem entre clusters antiferromagnéticos e a presença de campo magnético externo longitudinal. Nossos resultados indicam que magnetos com clusters são protótipos para a observação de congelamento inverso. Além disso, para níveis baixos de desordem, observamos o aparecimento da fase VSC induzida por campo externo, indicando que antiferromagnetos com clusters também são candidatos para a observação de fases vítreas induzidas por campo externo.Universidade Federal de Santa MariaBrasilFísicaUFSMPrograma de Pós-Graduação em FísicaCentro de Ciências Naturais e ExatasZimmer, Fábio Mallmannhttp://lattes.cnpq.br/6328420212181284Mombach, Jose Carlos Merinohttp://lattes.cnpq.br/7661373078999069Baierle, Rogério Joséhttp://lattes.cnpq.br/7565203547830128Tumelero, Milton Andrehttp://lattes.cnpq.br/0041450594172893Gusmão, Miguel Angelo Cavalheirohttp://lattes.cnpq.br/4913722698091490Schmidt, Mateus2019-05-09T14:44:34Z2019-05-09T14:44:34Z2019-01-11info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisapplication/pdfhttp://repositorio.ufsm.br/handle/1/16501porAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/info:eu-repo/semantics/openAccessreponame:Manancial - Repositório Digital da UFSMinstname:Universidade Federal de Santa Maria (UFSM)instacron:UFSM2019-05-10T06:02:28Zoai:repositorio.ufsm.br:1/16501Biblioteca Digital de Teses e Dissertaçõeshttps://repositorio.ufsm.br/ONGhttps://repositorio.ufsm.br/oai/requestatendimento.sib@ufsm.br||tedebc@gmail.comopendoar:2019-05-10T06:02:28Manancial - Repositório Digital da UFSM - Universidade Federal de Santa Maria (UFSM)false |
dc.title.none.fl_str_mv |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters Effects of geometrical frustration on disordered antiferromagnets with clusters |
title |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters |
spellingShingle |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters Schmidt, Mateus Clusters Antiferromagnetos Desordem Frustração Vidro de Spin Antiferromagnets Disorder Frustration Spin Glass CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
title_short |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters |
title_full |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters |
title_fullStr |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters |
title_full_unstemmed |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters |
title_sort |
Efeitos de frustração geométrica em antiferromagnetos desordenados com clusters |
author |
Schmidt, Mateus |
author_facet |
Schmidt, Mateus |
author_role |
author |
dc.contributor.none.fl_str_mv |
Zimmer, Fábio Mallmann http://lattes.cnpq.br/6328420212181284 Mombach, Jose Carlos Merino http://lattes.cnpq.br/7661373078999069 Baierle, Rogério José http://lattes.cnpq.br/7565203547830128 Tumelero, Milton Andre http://lattes.cnpq.br/0041450594172893 Gusmão, Miguel Angelo Cavalheiro http://lattes.cnpq.br/4913722698091490 |
dc.contributor.author.fl_str_mv |
Schmidt, Mateus |
dc.subject.por.fl_str_mv |
Clusters Antiferromagnetos Desordem Frustração Vidro de Spin Antiferromagnets Disorder Frustration Spin Glass CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
topic |
Clusters Antiferromagnetos Desordem Frustração Vidro de Spin Antiferromagnets Disorder Frustration Spin Glass CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
description |
In magnetic systems, frustration - which refers to the inhability to satisfy all the interactios simultaneously - has ravealed a rich phenomenology. In particular, disorder and geometrical features are possible sources of frustration. Systems that combine these two sources generally give rise to a number of challenging problems. In the present work, we approach the interplay between geometrical frustration (GF) and bond disorder, focusing in the rich phenomenology underlying the cluster spin glass (CSG) phase stabilization. In order to deal with this problem we considered the van Hemmen and the Sherrington-Kirkpatrick cluster models, as well as cluster mean-field methods. Our studies focused on the J1-J2 square, the antiferromagnetic kagome and the checkerboard Ising lattices with intercluster disorder. In the square and kagome lattices, we studied the CSG onset at low levels of disorder in geometrically frustrated systems, which is a problem with great experimental motivation. Our results indicate that the increase in frustration (by tuning J2=J1) reduces the minimum amount of disorder needed to stabilize the CSG in the square lattice. Moreover, for the kagome lattice, we found that an infinitesimal disorder leads to a CSG ground-state. This result can be compared to the experimental findings for the Co3Mg(OH)6Cl2 compound, that is pointed out as an experimental realization of the Ising kagome antiferromagnet. Moreover, we investigate the effects of GF on the onset of reentrant transitions. In this study, we considered a model with disorder between clusters in the presence of an external longitudinal magnetic field. Our results indicate that cluster magnets are prototypes for the observation of inverse freezing. Besides, at weak disorders, we observed the onset of field-induced CSG phases, indicating that cluster antiferromagnets are also candidates for field-induced glassy phases. |
publishDate |
2019 |
dc.date.none.fl_str_mv |
2019-05-09T14:44:34Z 2019-05-09T14:44:34Z 2019-01-11 |
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 |
http://repositorio.ufsm.br/handle/1/16501 |
url |
http://repositorio.ufsm.br/handle/1/16501 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.rights.driver.fl_str_mv |
Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ info:eu-repo/semantics/openAccess |
rights_invalid_str_mv |
Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
Universidade Federal de Santa Maria Brasil Física UFSM Programa de Pós-Graduação em Física Centro de Ciências Naturais e Exatas |
publisher.none.fl_str_mv |
Universidade Federal de Santa Maria Brasil Física UFSM Programa de Pós-Graduação em Física Centro de Ciências Naturais e Exatas |
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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1805922165450604544 |