Magnetostructural transitions and adiabatic temperature variation in polycrystal and single-crystal Ni2MnGa alloys

The magnetocaloric response of off-stoichiometric Ni2MnGa polycrystal and single-crystal samples with a Curie temperature coincident with the martensitic transition temperature was investigated. The direct measurement of temperature change (?Tad) during an adiabatic transformation under a maximum field variation ?H = 5.6×106 A/m (7 T) was performed. The polycrystalline sample shows a maximum ?Tad ? 1.5 K at a temperature close to the structural transition. The value of ?Tad and the 20 K span of the ?Tad peak encourage further studies of the effect of microstructure on the magnetocaloric response of Ni2MnGa.