Entropy change linked to the martensitic transformation in metamagnetic shape memory alloys Original Research Article

The magnetic contribution to the martensitic transformation entropy change plays a crucial role in the transition properties of metamagnetic shape memory alloys. This contribution leads to a common dependence of the total entropy change at the structural transformation, ΔStr, on the normalized temperature difference image (where image is the Curie temperature of the austenitic phase and Ttr is the transformation temperature) whose main feature is a decrease in ΔStr with increasing image. A phenomenological model based on a Bragg–Williams approximation has been proposed to describe the observed behaviour in terms of the evolution of the magnetic contribution to the total entropy change. The proposed approximation provides a good fitting between predicted and experimental entropy changes obtained for different Ni–Mn-based alloy systems.