Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)

Detalhes bibliográficos
Autor(a) principal: Souza, Marcos Vinicios de
Data de Publicação: 2013
Tipo de documento: Dissertação
Idioma: por
Título da fonte: Repositório Institucional da UFS
Texto Completo: https://ri.ufs.br/handle/riufs/5290
Resumo: In this work, our initial efforts have been directed to study the behavior of the magnetization as a function of temperature, calculated according to the approximate method of the anisotropy constants and the resolution of a Hamiltonian (that includes the crystal field) as exemplified for the DyAl2 compound. Furthermore, we investigated the magneto-thermal characteristics of some members of the RX2 series (R: rare earth, X: Al, Ni), including spin reorientation (SR), by using a model Hamiltonian, that consists of localized magnetic moments interacting via exchange and crystal field interaction, in the molecular-field approximation. We studied how the SR depends on the direction of the application of magnetic field, the intensity of this field and temperature. For the magnetic calculations, the problem of self-consistency was solved by using a computational routine developed in the Fortran 90 programming language. We emphasize that special attention was directed to the crystal field, because of its high relevance to the anisotropic characteristics of the RX2 studied compounds. Thus, in our attempts to study the peculiarities of the rare earth elements, due to crystal field effects, we have not only considered the intensity change, but the direction change of the applied field. In the cases of both Er+3 and Tb+3 compounds, we obtained second-order or continuous magnetization behavior along the polar angle axis. We stressed that the crystal field terms plays an important role in the first order spin reorientation for Dy+3 and Ho+3 compounds. First, it can be revealed by the discontinuity in the Cartesian components of the magnetization vector as a function of the polar angle. Second, the discontinuity is of great importance in the calculation of latent heat associated to the spin reorientation in the case where the first order transitions were observed. Finally, we were able to separate the first and second order contributions of the anisotropic magnetic entropy change, which is the main result of this work.
id UFS-2_3526f7e5dc28b048aee02b03b0a5b208
oai_identifier_str oai:ufs.br:riufs/5290
network_acronym_str UFS-2
network_name_str Repositório Institucional da UFS
repository_id_str
spelling Souza, Marcos Vinicios dehttp://lattes.cnpq.br/3515829175424514Plaza, Edison Jesús Ramírezhttp://lattes.cnpq.br/88226405996629912017-09-26T18:27:12Z2017-09-26T18:27:12Z2013-03-01https://ri.ufs.br/handle/riufs/5290In this work, our initial efforts have been directed to study the behavior of the magnetization as a function of temperature, calculated according to the approximate method of the anisotropy constants and the resolution of a Hamiltonian (that includes the crystal field) as exemplified for the DyAl2 compound. Furthermore, we investigated the magneto-thermal characteristics of some members of the RX2 series (R: rare earth, X: Al, Ni), including spin reorientation (SR), by using a model Hamiltonian, that consists of localized magnetic moments interacting via exchange and crystal field interaction, in the molecular-field approximation. We studied how the SR depends on the direction of the application of magnetic field, the intensity of this field and temperature. For the magnetic calculations, the problem of self-consistency was solved by using a computational routine developed in the Fortran 90 programming language. We emphasize that special attention was directed to the crystal field, because of its high relevance to the anisotropic characteristics of the RX2 studied compounds. Thus, in our attempts to study the peculiarities of the rare earth elements, due to crystal field effects, we have not only considered the intensity change, but the direction change of the applied field. In the cases of both Er+3 and Tb+3 compounds, we obtained second-order or continuous magnetization behavior along the polar angle axis. We stressed that the crystal field terms plays an important role in the first order spin reorientation for Dy+3 and Ho+3 compounds. First, it can be revealed by the discontinuity in the Cartesian components of the magnetization vector as a function of the polar angle. Second, the discontinuity is of great importance in the calculation of latent heat associated to the spin reorientation in the case where the first order transitions were observed. Finally, we were able to separate the first and second order contributions of the anisotropic magnetic entropy change, which is the main result of this work.Neste trabalho, nossos esforços iniciais foram direcionados a estudar o comportamento da magnetização em função da temperatura, calculado segundo o método aproximativo das constantes de anisotropia e da resolução de um hamiltoniano (que inclui o campo cristalino) como exemplificado para o composto DyAl2. Além disto, investigamos as características magneto-térmicas de alguns integrantes da série RX2 (R: Terra rara; X: Al, Ni), incluindo a reorientação de spin (RS), usando um hamiltoniano modelo que consiste de momentos magnéticos localizados interagentes via interações de troca e de campo cristalino, na aproximação do campo molecular. Estudamos como a RS depende da direção de aplicação do campo magnético, da sua intensidade e da temperatura. Para os cálculos magnéticos, o problema da auto consistência foi solucionado utilizando uma rotina, computacional desenvolvida na linguagem computacional Fortran 90. Ressaltamos que, uma atenção especial foi direcionada ao campo cristalino, por conta da sua alta relevância sobre as características anisotrópicas dos compostos RX2 estudados. Portanto, em nossas tentativas para estudar as peculiaridades dos elementos terras raras, devido aos efeitos do campo cristalino, não consideramos somente a mudança na intensidade, mas a variação na direção do campo aplicado. No caso dos compostos Er+3 e Tb+3, obteve-se um comportamento da magnetização de segunda ordem ou contínuo face à mudança do ângulo polar. Salientamos que os termos de campo cristalino desempenham um papel fundamental na reorientação de spin de primeira ordem para Dy+3 e Ho+3. Primeiro, tal transição pode ser revelada por uma descontinuidade nas componentes cartesianas do vetor de magnetização em função do ângulo polar. Segundo, a descontinuidade é de grande importância para o cálculo do calor latente associado à reorientação spin nos casos em que foram observadas as transições de primeira ordem. Finalmente, foi possível separar as contribuições de primeira e segunda ordem da variação de entropia magnética anisotrópica, o qual é o principal resultado deste trabalho.application/pdfporReorientação de spinTerras rarasCampo cristalinoAnisotropiaMagnetismoMateriais magnéticosTeoria do campo cristalinoCorrentes elétricasEletrostáticaTerras-rarasTroca de SpinParticulas de spinReorientation of spinRare EarthsCrystalline FieldAnisotropyCrystal field theoryEarths, RareElectric currentsElectrostaticsMagnetic materialsMagnetismSpin exchangeCNPQ::CIENCIAS EXATAS E DA TERRA::FISICAEstudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisPós-Graduação em Físicainfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFSinstname:Universidade Federal de Sergipe (UFS)instacron:UFSORIGINALMARCOS_VINICIOS_SOUZA.pdfapplication/pdf3755069https://ri.ufs.br/jspui/bitstream/riufs/5290/1/MARCOS_VINICIOS_SOUZA.pdfcc2aed4cbeecf0bd8c598ade5c44b011MD51TEXTMARCOS_VINICIOS_SOUZA.pdf.txtMARCOS_VINICIOS_SOUZA.pdf.txtExtracted texttext/plain137361https://ri.ufs.br/jspui/bitstream/riufs/5290/2/MARCOS_VINICIOS_SOUZA.pdf.txt3d2dd529bb9625b0c6c31a2c5060d50cMD52THUMBNAILMARCOS_VINICIOS_SOUZA.pdf.jpgMARCOS_VINICIOS_SOUZA.pdf.jpgGenerated Thumbnailimage/jpeg1336https://ri.ufs.br/jspui/bitstream/riufs/5290/3/MARCOS_VINICIOS_SOUZA.pdf.jpge025fed2d7b50c60e97c57fb1993039cMD53riufs/52902017-11-29 20:05:34.682oai:ufs.br:riufs/5290Repositório InstitucionalPUBhttps://ri.ufs.br/oai/requestrepositorio@academico.ufs.bropendoar:2017-11-29T23:05:34Repositório Institucional da UFS - Universidade Federal de Sergipe (UFS)false
dc.title.por.fl_str_mv Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
title Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
spellingShingle Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
Souza, Marcos Vinicios de
Reorientação de spin
Terras raras
Campo cristalino
Anisotropia
Magnetismo
Materiais magnéticos
Teoria do campo cristalino
Correntes elétricas
Eletrostática
Terras-raras
Troca de Spin
Particulas de spin
Reorientation of spin
Rare Earths
Crystalline Field
Anisotropy
Crystal field theory
Earths, Rare
Electric currents
Electrostatics
Magnetic materials
Magnetism
Spin exchange
CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
title_short Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
title_full Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
title_fullStr Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
title_full_unstemmed Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
title_sort Estudo da reorientação de spin nos compostos RX2 (R = terra rara; X: Al, Ni)
author Souza, Marcos Vinicios de
author_facet Souza, Marcos Vinicios de
author_role author
dc.contributor.author.fl_str_mv Souza, Marcos Vinicios de
dc.contributor.advisor1Lattes.fl_str_mv http://lattes.cnpq.br/3515829175424514
dc.contributor.advisor1.fl_str_mv Plaza, Edison Jesús Ramírez
dc.contributor.authorLattes.fl_str_mv http://lattes.cnpq.br/8822640599662991
contributor_str_mv Plaza, Edison Jesús Ramírez
dc.subject.por.fl_str_mv Reorientação de spin
Terras raras
Campo cristalino
Anisotropia
Magnetismo
Materiais magnéticos
Teoria do campo cristalino
Correntes elétricas
Eletrostática
Terras-raras
Troca de Spin
Particulas de spin
topic Reorientação de spin
Terras raras
Campo cristalino
Anisotropia
Magnetismo
Materiais magnéticos
Teoria do campo cristalino
Correntes elétricas
Eletrostática
Terras-raras
Troca de Spin
Particulas de spin
Reorientation of spin
Rare Earths
Crystalline Field
Anisotropy
Crystal field theory
Earths, Rare
Electric currents
Electrostatics
Magnetic materials
Magnetism
Spin exchange
CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
dc.subject.eng.fl_str_mv Reorientation of spin
Rare Earths
Crystalline Field
Anisotropy
Crystal field theory
Earths, Rare
Electric currents
Electrostatics
Magnetic materials
Magnetism
Spin exchange
dc.subject.cnpq.fl_str_mv CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
description In this work, our initial efforts have been directed to study the behavior of the magnetization as a function of temperature, calculated according to the approximate method of the anisotropy constants and the resolution of a Hamiltonian (that includes the crystal field) as exemplified for the DyAl2 compound. Furthermore, we investigated the magneto-thermal characteristics of some members of the RX2 series (R: rare earth, X: Al, Ni), including spin reorientation (SR), by using a model Hamiltonian, that consists of localized magnetic moments interacting via exchange and crystal field interaction, in the molecular-field approximation. We studied how the SR depends on the direction of the application of magnetic field, the intensity of this field and temperature. For the magnetic calculations, the problem of self-consistency was solved by using a computational routine developed in the Fortran 90 programming language. We emphasize that special attention was directed to the crystal field, because of its high relevance to the anisotropic characteristics of the RX2 studied compounds. Thus, in our attempts to study the peculiarities of the rare earth elements, due to crystal field effects, we have not only considered the intensity change, but the direction change of the applied field. In the cases of both Er+3 and Tb+3 compounds, we obtained second-order or continuous magnetization behavior along the polar angle axis. We stressed that the crystal field terms plays an important role in the first order spin reorientation for Dy+3 and Ho+3 compounds. First, it can be revealed by the discontinuity in the Cartesian components of the magnetization vector as a function of the polar angle. Second, the discontinuity is of great importance in the calculation of latent heat associated to the spin reorientation in the case where the first order transitions were observed. Finally, we were able to separate the first and second order contributions of the anisotropic magnetic entropy change, which is the main result of this work.
publishDate 2013
dc.date.issued.fl_str_mv 2013-03-01
dc.date.accessioned.fl_str_mv 2017-09-26T18:27:12Z
dc.date.available.fl_str_mv 2017-09-26T18:27:12Z
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/masterThesis
format masterThesis
status_str publishedVersion
dc.identifier.uri.fl_str_mv https://ri.ufs.br/handle/riufs/5290
url https://ri.ufs.br/handle/riufs/5290
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
dc.publisher.program.fl_str_mv Pós-Graduação em Física
dc.source.none.fl_str_mv reponame:Repositório Institucional da UFS
instname:Universidade Federal de Sergipe (UFS)
instacron:UFS
instname_str Universidade Federal de Sergipe (UFS)
instacron_str UFS
institution UFS
reponame_str Repositório Institucional da UFS
collection Repositório Institucional da UFS
bitstream.url.fl_str_mv https://ri.ufs.br/jspui/bitstream/riufs/5290/1/MARCOS_VINICIOS_SOUZA.pdf
https://ri.ufs.br/jspui/bitstream/riufs/5290/2/MARCOS_VINICIOS_SOUZA.pdf.txt
https://ri.ufs.br/jspui/bitstream/riufs/5290/3/MARCOS_VINICIOS_SOUZA.pdf.jpg
bitstream.checksum.fl_str_mv cc2aed4cbeecf0bd8c598ade5c44b011
3d2dd529bb9625b0c6c31a2c5060d50c
e025fed2d7b50c60e97c57fb1993039c
bitstream.checksumAlgorithm.fl_str_mv MD5
MD5
MD5
repository.name.fl_str_mv Repositório Institucional da UFS - Universidade Federal de Sergipe (UFS)
repository.mail.fl_str_mv repositorio@academico.ufs.br
_version_ 1802110726302597120