Otimização das propriedades magnetocalóricas das ligas de Heusler Ni50Mn34,5In15,5 pela adição de Ga

• Ano de defesa: 2011
• Autor(a) principal: Guimarães, Carlos Eduardo Alves
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Espírito Santo; BR; Mestrado em Física; Centro de Ciências Exatas; UFES; Programa de Pós-Graduação em Física
• Palavras-chave em Português: Magnetismo; Matéria condensada; Física; 53
• Link de acesso: http://repositorio.ufes.br/handle/10/7423

In this work, the magnetic entropy change was observed experimentally in the nonstoichiometric Heusler alloys Ni50Mn34,5(In1-xGax)15,5 with x = (0; 0,015; 0,03; 0,05; 0,075). The structural characterization of these alloys was carried by X-ray diffractometry. The magnetocaloric properties have been quantified by magnetization measurements as a function of the temperature and applied magnetic field. Magnetization measurement has shown a complex behavior due to the existence of the magneto-structural transitions in all Ga concentrations studied. The increasing of Ga concentrations in these samples resulted in an increase of the martensitic temperature, however, with no significant changes in the Curie temperature of austenite phase. The magnetization measurements as a function of the magnetic field have indicated the presence of metamagnetic transition.The inverse magnetocaloric effect was observed in all samples with structural transition of martensiticaustenitic type. Large magnetic entropy values observed for x=0,03 (36 J/kg.K) in an relatively low magnetic applied field (30 kOe) make the Ga-doped alloys good candidates for technological application as a solid refrigerant