Mechanically induced disorder and crystallization process in Ni-Mn-In ball-milled alloys
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Date
2016-12-25Author
Sánchez Alarcos, Vicente
Recarte Callado, Vicente
Pérez de Landazábal, José Ignacio
Larumbe, Silvia
Caballero Flores, Rafael
García Martínez, José Ángel
Rodríguez Velamazán, José Alberto
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Journal of Alloys and Compounds 689 : 983-991 (2016)
Abstract
[EN] High mechanical deformation has been induced in a Ni-Mn-In metamagnetic shape memory alloy by means of ball milling. The evolution of both the martensitic transformation and the magnetic properties associated to the microstructural variations has been characterized. The as-milled nanometric particles display an amorphous structure with a frustrated magnetic state compatible with a canonical spin-glass. On heating, an abrupt crystallization process occurs around 500 K leading to a cubic B2 structure, which, in turn, does not show martensitic transformation. Modified Arrott plots point to competing long- and short-range magnetic couplings in the B2 structure. On further heating, a relaxation process takes place above 700 K concurrently with a B2-L21 atomic ordering, giving rise to an anomalous two-step thermal expansion. The combined effect of both processes makes possible the subsequent occurrence of a martensitic transformation, which takes place at the same temperature than in the bulk. The large relative-cooling-power linked to the magnetocaloric effect at the martensitic transformation in the annealed powder makes it interesting for practical applications of magnetic refrigeration at nanoscale.