The magneto-structural transformation and the associated magnetic entropy change were studied in the ferromagnetic shape memory alloys Ni 2Mn0.75Cu0.25Ga and Ni2MnGa 0.88Cu0.12 by using magnetization measurements performed around the martensite transformation temperature TM and the Curie temperature TC. The direct transition from the paramagnetic austenite phase (PM phase) to the ferromagnetic martensite phase (FM phase) was observed in both alloys. In a magnetic field of 2.0 T, the Ni2Mn 0.75Cu0.25Ga and Ni2MnGa0.88Cu 0.12 alloys showed large magnetic entropy changes of -ΔS M = 15.2 J/kg K at 302 K and -7.5 J/kg K at 333 K, respectively. The magnetic entropy change of Ni2Mn0.75Cu0.25Ga is larger than that of the polycrystalline Ni2.19Mn0.81Ga alloy. Theoretical calculations were also performed, and they agreed well with the experimental determinations of -ΔSM.
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