Otimização das propriedades magnetocalóricas das ligas de Heusler Ni50Mn34,5In15,5 pela adição de Ga
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2011-12-16
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Guimarães, Carlos Eduardo Alves
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Universidade Federal do Espírito Santo
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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
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GUIMARÃES, Carlos Eduardo Alves. Otimização das propriedades magnetocalóricas das ligas de Heusler Ni50Mn34,5In15,5 pela adição de Ga. 2011. Dissertação (Mestrado em Física) – Universidade Federal do Espírito Santo, Vitória, 2011.