Reversibility and irreversibility of magnetocaloric effect in a metamagnetic shape memory alloy under cyclic action of a magnetic field

We have studied adiabatic temperature change Delta T-ad in a Ni50Mn36Co1Sn13 metamagnetic shape memory alloy. An irreversible character of Delta T-ad has been observed in the vicinity of the reverse martensitic transformation. In this region, cyclic application of the magnetic field converts comparatively large inverse magnetocaloric effect (MCE) with Delta T-ad(max)=-0.8 K to a weaker conventional MCE (Delta T-ad(max)=0.3 K). The crossover of Delta T-ad has been attributed to the irreversible character of the magnetic field-induced transformation and the closeness of the martensitic transformation and Curie temperature of the austenitic phase T-C(A). (C) 2010 American Institute of Physics. [doi: 10.1063/1.3476348]