O efeito magnetocalórico nas ligas Heusler Ni54[Mn(1-x)Fex]19Ga27
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Data
2008-03-28
Autores
Sardinha, Farley Correia
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Universidade Federal do Espírito Santo
Resumo
In this work, magnetic entropy change of nonstoichiometric Ni54[Mn(1-x)Fex]19Ga27 Heusler alloys was experimentally verified by partial substitution (up to 50%) of the Mn atoms by magnetic Fe atoms. Such study was mainly concentrated in the magneto-structural transformation region, at low temperatures. The analysis of X-ray diffraction patterns indicate that the partial substitution of Mn atoms by Fe atoms causes predominance of the L21 -phase, however accompanied by spurious phases. The magnetization measurements as a function of the temperature in the low magnetic field reveals that, in all concentration range (0 x 0.5), the system presents a magnetic transition (Ferromagnetic Paramagnetic) at a temperature, TC, near the room temperature, when the material lay in the austenitic phase. Moreover, as many others Heusler alloys, the material undergoes a martensitic structural transition at low temperatures, TM. As the Fe concentration increases, the Curie temperature, TC, undergoes a little variation, increasing around 5%, while TM decreases slowly and monotonically. The magnetic entropy change, for a field of 5T, presents a maximum SM = - 9,3 J/kg.K, for x = 0.1, at a temperature of 250K, and than decreases for x 0.3, changing linearly with the maximum applied field.
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Magnetic refrigeration , Magnetocaloric effect , Heusler alloys , Refrigeração magnética , Efeito magnetocalórico , Ligas Heusler
Citação
SARDINHA, Farley Correia. O efeito magnetocalórico nas ligas Heusler Ni54[Mn(1-x)Fex]19Ga27. 2008. 93 f. Dissertação (Mestrado em Física) – Programa de Pós-Graduação em Física, Universidade Federal do Espírito Santo, Centro de Ciências Exatas e da Terra, Vitória, 2008.