Specific heat and entropy change during martensitic transformation in Ni50Mn50-xGax ferromagnetic shape memory alloys

Specific heat was systematically measured for Ni50Mn50-xGax ferromagnetic shape memory alloys near the martensitic transformation temperatures. Martensitic and intermediate transformations and magnetic transitions in the parent and martensite phases were directly observed via specific heat measurements. Entropy change during the intermediate transformation was successfully estimated by direct measurement. Entropy change during the martensitic transformation was also analyzed; it generally decreases with decreasing Ga concentration. Anomalous behavior of the entropy change during martensitic transformation was observed near the magnetic transitions, and was found to attributable to the magnetic contribution by a qualitative examination based on the results of specific heat measurements. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.