Giant entropy change at the co-occurrence of structural and magnetic transitions in the Ni2.19 Mn0.81 Ga Heusler alloy

We have studied the isothermal entropy change around a first-order structural transformation and in correspondence to the second-order Curie transition in the ferromagnetic Heusler alloy Ni2.15Mn0.85Ga. The results have been compared with those obtained for the compositionNi2.19Mn0.81Ga, in which the martensitic structural transformation and the magnetic transition occur simultaneously. With a magnetic field span from 0 to 1.6T, the magnetic entropy change reaches the value of 20J/kgK when transitions are co-occurring, while 5 J/kgK is found when the only structural transition occurs.