Propriedades estruturais e magnéticas de compostos intermetálicos contendo terras raras

• Ano de defesa: 2016
• Autor(a) principal: Mercena, Samuel Gomes de
• Orientador(a): Duque, José Gerivaldo dos Santos
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Sergipe
• Programa de Pós-Graduação: Pós-Graduação em Física
• País: Brasil
• Palavras-chave em Português: Física; Terras-raras; Magnetismo; Metais; Compostos intermetálicos; Campos magnéticos; Sólidos; Ferromagnetismo; Antiferromagnetismo
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://ri.ufs.br/handle/riufs/5372

In this work, structural and magnetic properties of TRNi3Al9 (with TR=Er e Tb) and Er(Ni1−xCux)3Al9 intermetallic compounds are investigated. Single crystal samples were grown by the flux method which was efficient once we obtained single crystals with good quality for Er−Ni−Al, Tb−Ni−AL e Er−Ni−Cu−Al systems. The structural and magnetic characterizations of the samples were performed by the X-ray diffraction measurements and magnetic susceptibility measurements as a function of temperature and applied magnetic field, respectively. The analysis of X-ray diffraction results carried out via the Rietveld method for the TRNi3Al9 (with TR=Er e Tb) system show the formation of a single phase with crystal structure of type ErNi3Al9 which has trigonal symmetry belonging to the space group R32. In this particular case, the magnetization measurements as a function of temperature and magnetic field reveal the presence of a strong magnetic anisotropy due likely to crystal electric field (CEF) effects. In order to study the influence of the CEF on the physical properties of samples we have fitted the experimental data through a mean-field model. Moreover, the analysis of X-ray diffraction measurements allied to Rietveld refinement for Er(Ni1−xCux)3Al9 compounds shows a change of crystal symmetry from trigonal to tetragonal, as a function of the Cu concentration. However, the magnetic susceptibility measurements as a function of temperature show no significant changes in Néel temperature (TN) of compounds.