Magnetismo observado por espectroscopia Mössbauer no supercondutor BaFe1,908 As2Ni0,092

• Ano de defesa: 2014
• Autor(a) principal: Cardoso, Fernando Lopes
• Outros Autores: [e-mail]
• Orientador(a): López Giménez, Ada Petronila
• Banca de defesa: Sosman, Lilian Pantoja , Fonseca, Raul José da Silva Câmara Mauricio da , Munévar Cagigas, Julián Andrés , Pedro, Sandra da Silva
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade do Estado do Rio de Janeiro
• Programa de Pós-Graduação: Programa de Pós-Graduação em Física
• Departamento: Centro de Tecnologia e Ciências::Instituto de Física Armando Dias Tavares
• País: Brasil
• Palavras-chave em Português: Supercondutividade; Magnetismo; Mossbauer, Efeito; Campos magnéticos; Pnictideos; Efeito Mössbauer; Campo magnético hiperfino
• Palavras-chave em Inglês: Superconductivity; Magnetism; Mossbauer effect; Magnetic fields; Pnictides; Hyperfine Magnetic Field
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA::SUPERCONDUTIVIDADE
• Link de acesso: http://www.bdtd.uerj.br/handle/1/23603

Superconductivity in magnetic materials remains a topic that intrigues scientists, as historically it was understood that magnetism breaks Cooper pairs and destroys superconductivity. In 2006, a compound based on iron was discovered that exhibits a superconducting phase. Since then, various iron-based compounds have been created, demonstrating the phenomenon of superconductivity. These new compounds represent a new type of unconventional superconductors and have sparked interest in the academic community because iron is a very abundant element on the planet. A new challenge is to understand how superconductivity interacts with magnetism; there is currently no unified theory explaining how this new range of compounds can exhibit coexistence or competition between superconductivity and magnetism. This study investigated a superconducting sample of BaFe0.908As2Ni0.092 using 57Fe Mössbauer spectroscopy at different temperatures. The spectra were fitted in two different ways, and the results were analyzed. A hyperfine magnetic field was determined, which arises at approximately 40 K, gradually increases to a maximum of 1.45 Tesla as the temperature decreases to about 18 K, after which it begins to decrease. It was observed that the maximum value of the hyperfine magnetic field coincides with the superconducting transition temperature. This behavior indicates the existence of competition between superconductivity and magnetism, as the onset of the superconducting phase disturbs the magnetic moments of iron, leading to a decay in the hyperfine magnetic field, which is accompanied by a decrease in the magnetic fraction of the sample.