Estudo de propriedades físicas de oxi-boratos assistido pela análise do perfil de densidade eletrônica obtido através do Método da Entropia Máxima

• Ano de defesa: 2007
• Autor(a) principal: Sarrat, Felipe dos Santos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Programa de Pós-graduação em Física; Física
• Palavras-chave em Português: Método de entropia máxima; Análise de perfil; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://app.uff.br/riuff/handle/1/19152

In this thesis is proposed a new tool for the analysis of physical properties of materials, based on the conjoint use of the Ligand Field Theory, of the Theory of Antiferromagnetism and of an alternative method for obtaining electron densities of crystals, known as the Maximum-Entropy Method. This tool is shown by a study which aims the explanation of the origin of the three-dimensional antiferromagnetic ordering of the pyroborate Mn2B2O5 and, for this purpose, the Maximum-Entropy Method has been employed in order to obtain the bias-free electron density configuration of the unit cell. The conjoint analysis of the electron density maps and the magnetic measurements of the magnetization derivatives as a function of the applied magnetic field has led to the identification of the magnetic unit cell and the determination of a hierarchy of exchange interactions responsible for the observed long-range magnetic order, together with the values of these exchange interactions and the corresponding overlapped magnetic orbitals. The Maximum-Entropy Method also has been employed for the examination of the validity of the interpretation of transport properties of the ludwigite Fe3O2BO3, given in a previous Mössbauer spectroscopy study made on this material.