Phase transitions and magnetic properties of Cu and Fe doped Ni2Mn0.55Cu0.35Fe0.10Ga Heusler alloy

The phase transitions and associated magnetic properties of Ni2Mn0.55Cu0.35Fe0.10Ga have been studied by dc magnetization and electrical resistivity measurements. A tetragonal crystal structure was identified at room temperature by powder x-ray diffraction measurements. The temperature dependence of magnetization data obtained while heating revealed two distinct transitions at 338 K and 368 K. On cooling the transitions were observed at 334 K and 355 K. The lower temperature transition showed a thermal hysteresis of ≈4 K, while the higher temperature transition exhibited a thermal hysteresis of ≈13 K. The temperature dependence of the electrical resistivity and isothermal entropy changes obtained data indicated that the transition at 338 K is a second order transition while the one at 368 K is a first order phase transition. For a field change of 5 T, a maximum entropy change of −3.5 J kg−1 K−1 has been observed. The experimental data showed that for both heating and cooling the martensitic phase transition occurred in a paramagnetic state in Ni2Mn0.55Cu0.35Fe0.10Ga.