Dependence of the martensitic transformation and magnetic transition on the atomic order in Ni-Mn-In metamagnetic shape memory alloys

Abstract

The analysis of atomic order and its influence on the magnetic and structural properties of Ni-Mn-In metamagnetic shape memory alloys has been performed. The effect of the different thermal treatments on the magnetic and structural transformation temperatures, as well as on the thermodynamics of the martensitic transformation, has been made by calorimetric measurements. The evolution of the degree of long-range atomic order with temperature has been determined by neutron diffraction experiments, thus confirming the effect of thermal treatments on the atomic order. Calorimetric and structural results allow thermal treatments to be directly related to atomic order, and to allow the effect of the atomic order on the martensitic and magnetic transformations in Ni-Mn-In alloys to be quantified. The thermodynamics of the martensitic transformation depends on the atomic order as indicated out by its influence on the transformation entropy. In addition, a correlation between the transformation entropy and changes in the magnetic-field-induced transformation temperatures has been found through the evolution of the atomic order. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.