Entropy change linked to the magnetic field induced martensitic transformation in a Ni–Mn–In–Co shape memory alloy

Abstract

Experimental results on the temperature dependence of the entropy change induced by magnetic field in a Ni–Mn–In–Co ferromagnetic shape memory alloy have been analyzed. Different behaviors of the entropy change ΔS versus temperature have been observed, depending on the value of polarizing magnetic field. In addition, the magnetocaloric effect shows over certain temperature range, a limit value corresponding to the transformation entropy ΔStr. To explain the experimental results, a model, which takes into account the value of the martensitic transformation temperature shift and the transformation temperature range, has been proposed. The model allows to estimate the entropy change as a function of temperature and applied magnetic field from a few experimental data and therefore a first estimation of the refrigerant capacity of the system can be done.