Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb)
Autor(a) principal: | |
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Data de Publicação: | 2020 |
Tipo de documento: | Tese |
Idioma: | eng |
Título da fonte: | Biblioteca Digital de Teses e Dissertações da USP |
Texto Completo: | https://www.teses.usp.br/teses/disponiveis/43/43134/tde-18122020-021258/ |
Resumo: | In the geometrically frustrated magnets, competing magnetic interactions together with the lattice structure inhibit the system of establishing long-range order. The tetrahedral arrangement of the magnetic R ions in the pyrochlores R2M2O7 manifests the development of intriguing magnetic states which have been investigated vastly in the literature. However, the physical properties of the R ions in frustrated magnets are strongly affected when structural disorder is introduced. Recently, research probing disorder has provided interesting insights in XY pyrochlores, spin ices and spin liquids. In this work, we study the dilution of the nonmagnetic sublattice of M (Ti/Sn) in the pyrochlores Er2Ti2-xSnxO7 (x=0-2), and the defect-fluorites R2Zr2O7 (R = Dy, Ho and Tb) in which the R moments randomly reside on a sublattice together with the nonmagnetic Zr ions. The erbium compounds possess a strong local planar anisotropy, and with the dilution of the M sublattice, we study the evolution of the magnetic moment for all the x compositions starting from the 2 to the Palmer-Chalker configuration trough a specific-heat analysis. In-field experiments suppress the long-range order transition and the H-T phase diagram exhibits two different trends for small and high x values. Ac magnetic susceptibility and specific heat studies have been performed in the disordered-fluorites R2Zr2O7. Antiferromagnetic correlations and similar magnetic moment were found in Dy2Zr2O7 and Ho2Zr2O7, different from the ferromagnetic interactions in spin ices Dy2Ti2O7 and Ho2Ti2O7. Magnetic specific heat revealed a correlation broad peak around 2 K for the disordered fluorites as well as no Pauling\'s residual entropy was observed, contrary to the pyrochlore spin ices. Disorder in both fluorites preclude the development of spin-ice correlations and exhibit fluctuating spins; with a significant amount of susceptibility, which do not freeze into a canonical spin glass. Neutron scattering in Dy2Zr2O7 confirms no long-range order and antiferromagnetic correlations which remain dynamic down to 40 mK. These correlations extend over the length of 6.6 A and with an external field of 4 T expand to 23.6 A. Tb2Zr2O7 presents no long-range order and exhibits spin fluctuations down to 100 mK. Dynamic measurements display a frequency-dependent maximum and different models to its shift temperature reveal a canonical spin-glass transition around 2.2 K. |
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Biblioteca Digital de Teses e Dissertações da USP |
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Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb)Magnetismo geometricamente frustrado no pirocloro Er2Ti2-xSnxO7 e nas fluoritas desordenadas R2Zr2O7 (R = Dy, Ho, Tb)Disordered FluoritesFluoritas DesordenadasGeometrically Frustrated MagnetismMagnetos Geometricamente FrustradosPiroclorosPyrochloresIn the geometrically frustrated magnets, competing magnetic interactions together with the lattice structure inhibit the system of establishing long-range order. The tetrahedral arrangement of the magnetic R ions in the pyrochlores R2M2O7 manifests the development of intriguing magnetic states which have been investigated vastly in the literature. However, the physical properties of the R ions in frustrated magnets are strongly affected when structural disorder is introduced. Recently, research probing disorder has provided interesting insights in XY pyrochlores, spin ices and spin liquids. In this work, we study the dilution of the nonmagnetic sublattice of M (Ti/Sn) in the pyrochlores Er2Ti2-xSnxO7 (x=0-2), and the defect-fluorites R2Zr2O7 (R = Dy, Ho and Tb) in which the R moments randomly reside on a sublattice together with the nonmagnetic Zr ions. The erbium compounds possess a strong local planar anisotropy, and with the dilution of the M sublattice, we study the evolution of the magnetic moment for all the x compositions starting from the 2 to the Palmer-Chalker configuration trough a specific-heat analysis. In-field experiments suppress the long-range order transition and the H-T phase diagram exhibits two different trends for small and high x values. Ac magnetic susceptibility and specific heat studies have been performed in the disordered-fluorites R2Zr2O7. Antiferromagnetic correlations and similar magnetic moment were found in Dy2Zr2O7 and Ho2Zr2O7, different from the ferromagnetic interactions in spin ices Dy2Ti2O7 and Ho2Ti2O7. Magnetic specific heat revealed a correlation broad peak around 2 K for the disordered fluorites as well as no Pauling\'s residual entropy was observed, contrary to the pyrochlore spin ices. Disorder in both fluorites preclude the development of spin-ice correlations and exhibit fluctuating spins; with a significant amount of susceptibility, which do not freeze into a canonical spin glass. Neutron scattering in Dy2Zr2O7 confirms no long-range order and antiferromagnetic correlations which remain dynamic down to 40 mK. These correlations extend over the length of 6.6 A and with an external field of 4 T expand to 23.6 A. Tb2Zr2O7 presents no long-range order and exhibits spin fluctuations down to 100 mK. Dynamic measurements display a frequency-dependent maximum and different models to its shift temperature reveal a canonical spin-glass transition around 2.2 K.Nos magnetos geometricamente frustrados, a competição entre interações magnéticas, em conjunto com a geometria da rede, inibem o estabelecimento de uma ordem de longo alcance. O arranjo tetraédrico dos íons magnéticos R nos pirocloros R2M2O7 tem apresentado interessantes estados magnéticos, e muitos deles têm sido discutidos vastamente na literatura. Entretanto, as propriedades físicas dos íons R nos magnetos frustrados são fortemente modificadas na presença de desordem estrutural. Recentemente, a inclusão de desordem tem providenciado novas perspectivas no estudo dos pirocloros XY, nos gelos de spin e nos líquidos de spin. Neste trabalho, nós estudamos a diluição da subrede não magnética de M (Ti/Sn) nos pirocloros Er2Ti2-xSnxO7 (x = 0 - 2), e as fluoritas desordenadas R2Zr2O7 (R= Dy, Ho e Tb), que possuem seus íons R e Zr localizados aleatoriamente na mesma subrede. Os compostos de érbio apresentam uma anisotropia planar de spin; nós estudamos a evolução do momento magnético, começando no 2, até a configuração Palmer-Chalker para diferentes valores x do Er2Ti2-xSnxO7, usando dados de calor específico. Experimentos de susceptibilidade magnética ac e de calor específico foram realizados nas fluoritas desordenadas R2Zr2O7; interações antiferromagnéticas e valores de momento magnéticos parecidos foram determinados no Dy2Zr2O7 e Ho2Zr2O7, divergindo das interações ferromagnéticas nos gelos de spin Dy2Ti2O7 e Ho2Ti2O7. A contribuição magnética ao calor específico apresenta um máximo associado a correlações em 2 K nas fluoritas desordenadas e uma ausência da entropia residual, de maneira oposta aos pirocloros gelos de spin. A desordem estrutural nas fluoritas exclui a possibilidade de correlações do tipo gelo de spin; esses compostos exibem flutuações de spin, junto com uma considerável quantidade de susceptibilidade, sem apresentar um estado canônico de vidro de spin. Espalhamento de nêutrons no Dy2Zr2O7 confirmam a ausência de ordem de longo alcance e a existência de correlações magnéticas que se mantêm dinâmicas em 40 mK; essas correlações se estendem por 6.6 A e na presença de campo magnético de 4 T, elas crescem até 23.6 A. Tb2Zr2O7 não apresenta ordem de longo alcance e temos flutuações de spin abaixo de 100 mK. Medidas dinâmicas apresentam um máximo com dependência na frequência aplicada. A mudança da posição do máximo foi ajustada usando diferentes modelos, mostrando uma transição para um estado canônico de vidro de spin em 2.2 K.Biblioteca Digitais de Teses e Dissertações da USPFreitas, Rafael Sá deRamón, Jonathan Gustavo Acosta2020-12-01info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisapplication/pdfhttps://www.teses.usp.br/teses/disponiveis/43/43134/tde-18122020-021258/reponame:Biblioteca Digital de Teses e Dissertações da USPinstname:Universidade de São Paulo (USP)instacron:USPLiberar o conteúdo para acesso público.info:eu-repo/semantics/openAccesseng2021-01-23T02:35:02Zoai:teses.usp.br:tde-18122020-021258Biblioteca Digital de Teses e Dissertaçõeshttp://www.teses.usp.br/PUBhttp://www.teses.usp.br/cgi-bin/mtd2br.plvirginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.bropendoar:27212021-01-23T02:35:02Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)false |
dc.title.none.fl_str_mv |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) Magnetismo geometricamente frustrado no pirocloro Er2Ti2-xSnxO7 e nas fluoritas desordenadas R2Zr2O7 (R = Dy, Ho, Tb) |
title |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) |
spellingShingle |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) Ramón, Jonathan Gustavo Acosta Disordered Fluorites Fluoritas Desordenadas Geometrically Frustrated Magnetism Magnetos Geometricamente Frustrados Pirocloros Pyrochlores |
title_short |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) |
title_full |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) |
title_fullStr |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) |
title_full_unstemmed |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) |
title_sort |
Geometrically frustrated magnetism in the pyrochlore Er2Ti2-xSnxO7 and in the disordered fluorites R2Zr2O7 (R = Dy, Ho, Tb) |
author |
Ramón, Jonathan Gustavo Acosta |
author_facet |
Ramón, Jonathan Gustavo Acosta |
author_role |
author |
dc.contributor.none.fl_str_mv |
Freitas, Rafael Sá de |
dc.contributor.author.fl_str_mv |
Ramón, Jonathan Gustavo Acosta |
dc.subject.por.fl_str_mv |
Disordered Fluorites Fluoritas Desordenadas Geometrically Frustrated Magnetism Magnetos Geometricamente Frustrados Pirocloros Pyrochlores |
topic |
Disordered Fluorites Fluoritas Desordenadas Geometrically Frustrated Magnetism Magnetos Geometricamente Frustrados Pirocloros Pyrochlores |
description |
In the geometrically frustrated magnets, competing magnetic interactions together with the lattice structure inhibit the system of establishing long-range order. The tetrahedral arrangement of the magnetic R ions in the pyrochlores R2M2O7 manifests the development of intriguing magnetic states which have been investigated vastly in the literature. However, the physical properties of the R ions in frustrated magnets are strongly affected when structural disorder is introduced. Recently, research probing disorder has provided interesting insights in XY pyrochlores, spin ices and spin liquids. In this work, we study the dilution of the nonmagnetic sublattice of M (Ti/Sn) in the pyrochlores Er2Ti2-xSnxO7 (x=0-2), and the defect-fluorites R2Zr2O7 (R = Dy, Ho and Tb) in which the R moments randomly reside on a sublattice together with the nonmagnetic Zr ions. The erbium compounds possess a strong local planar anisotropy, and with the dilution of the M sublattice, we study the evolution of the magnetic moment for all the x compositions starting from the 2 to the Palmer-Chalker configuration trough a specific-heat analysis. In-field experiments suppress the long-range order transition and the H-T phase diagram exhibits two different trends for small and high x values. Ac magnetic susceptibility and specific heat studies have been performed in the disordered-fluorites R2Zr2O7. Antiferromagnetic correlations and similar magnetic moment were found in Dy2Zr2O7 and Ho2Zr2O7, different from the ferromagnetic interactions in spin ices Dy2Ti2O7 and Ho2Ti2O7. Magnetic specific heat revealed a correlation broad peak around 2 K for the disordered fluorites as well as no Pauling\'s residual entropy was observed, contrary to the pyrochlore spin ices. Disorder in both fluorites preclude the development of spin-ice correlations and exhibit fluctuating spins; with a significant amount of susceptibility, which do not freeze into a canonical spin glass. Neutron scattering in Dy2Zr2O7 confirms no long-range order and antiferromagnetic correlations which remain dynamic down to 40 mK. These correlations extend over the length of 6.6 A and with an external field of 4 T expand to 23.6 A. Tb2Zr2O7 presents no long-range order and exhibits spin fluctuations down to 100 mK. Dynamic measurements display a frequency-dependent maximum and different models to its shift temperature reveal a canonical spin-glass transition around 2.2 K. |
publishDate |
2020 |
dc.date.none.fl_str_mv |
2020-12-01 |
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 |
https://www.teses.usp.br/teses/disponiveis/43/43134/tde-18122020-021258/ |
url |
https://www.teses.usp.br/teses/disponiveis/43/43134/tde-18122020-021258/ |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
|
dc.rights.driver.fl_str_mv |
Liberar o conteúdo para acesso público. info:eu-repo/semantics/openAccess |
rights_invalid_str_mv |
Liberar o conteúdo para acesso público. |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.coverage.none.fl_str_mv |
|
dc.publisher.none.fl_str_mv |
Biblioteca Digitais de Teses e Dissertações da USP |
publisher.none.fl_str_mv |
Biblioteca Digitais de Teses e Dissertações da USP |
dc.source.none.fl_str_mv |
reponame:Biblioteca Digital de Teses e Dissertações da USP instname:Universidade de São Paulo (USP) instacron:USP |
instname_str |
Universidade de São Paulo (USP) |
instacron_str |
USP |
institution |
USP |
reponame_str |
Biblioteca Digital de Teses e Dissertações da USP |
collection |
Biblioteca Digital de Teses e Dissertações da USP |
repository.name.fl_str_mv |
Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP) |
repository.mail.fl_str_mv |
virginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.br |
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1809090847605522432 |