Crystal Structure, Phase Stability and Magnetic Properties of Cu-Doped Ni<sub>2</sub>MnGa Alloys from First-Principles Calculations

The effects of Cu addition on the crystal structure, phase stability and magnetic properties of Ni8Mn4-xGa4Cux (x=0, 0.5, 1, 1.5 and 2) ferromagnetic shape memory alloys are systematically investigated by first-principles calculations. The formation energy results indicate that the added Cu preferentially occupies the Mn sites in Ni2MnGa alloy. The formation energy results indicate that ferromagnetic austenite is more stable than the paramagnetic one. The ferromagnetic state becomes instable and paramagnetic state becomes more stable when Mn is gradual substituted by Cu. Furthermore, the electronic density of states gives rise to the difference in the magnetic properties.