Phase transformation, thermoelastic and magnetic properties of Ni50Mn30Ga20−xCux ferromagnetic shape memory alloys

Effect of addition of Cu on phase transformation temperatures, enthalpy and entropy changes, Curie temperature, magnetization saturation were investigated in Ni-Mn-Ga ferromagnetic shape memory alloy. The results show that the Ni50Mn30Ga20−xCux alloys exhibit thermoelastic martensitic transformation. The martensitic and reverse martensitic transformation temperatures, enthalpy and entropy changes and thermal hysteresis increase with increase of Cu content. Martensite structure changes from 7 M with 0-0.5 at.% Cu to non-modulated T martensite when the content of Cu is more than 0.5 at.%. In addition, the Curie temperature almost remains unchanged at low-Cu content and subsequently decreases obviously. Magnetization saturation of alloys decrease with increasing Cu content since it is sensitive to ordered atomic arrangement.