Ab initio study of properties of Co- and Cu- doped Ni-Mn-Ga alloys

The influence of Co and Cu doping on Ni-Mn-Ga alloy is investigated using the first-principles exact muffin-tin orbital method in combination with the coherent-potential approximation. The energy difference between the austenite (A) and the nonmodulated (NM) martensite ΔEA-NM depends linearly on the Cu concentration and distribution, with a minimum for all Cu at Mn sites and a maximum for all Cu at Ga sites. For alloys simultaneously doped by Co in Ni sublattice and Cu in Mn or Ga sublattice, the effects of the individual dopants on ΔEA-NM and (c/a)NM and are almost independent. The alloy with composition Ni46Co4Mn24Ga22Cu4 exhibits decreased equilibrium (c/a)NM and increased ΔEA-NM in comparison with Ni50Mn25Ga25, which is in agreement with the previous experimental results.