Magnetic-field-induced martensitic transformation in MnNiAl:Co alloys

Abstract

A series of Heusler-type MnNiCoAl alloys have been prepared, and the composition dependence of the martensitic transformation has been investigated. Due to the formation of a local Mn-Co-Mn ferromagnetic structure in the antiferromagnetic matrix, a large magnetization difference of 48 Am2/kg and a driving efficiency of 2.14 K/T can be observed in Mn50Ni32Co6Al12 sample in which a field-induced transformation can be realized. X-ray diffraction results further indicate that the high temperature phase has a high level of atomic disorder which causes an increase of the thermal hysteresis of the transformation when increasing Co content.