First-principles study of martensitic transformation and magnetic properties of carbon doped Ni–Mn–Sn Heusler alloys

• The results show that the martensitic transformation can be realized in all series of carbon doped Ni2Mn1.5Sn0.5 − xCx alloys with tetragonal ratio of 1.34, 1.40,1.42 and 1.44, respectively for x=0.125,0.25,0.375 and 0.5x=0.125,0.25,0.375 and 0.5.
• The total energy difference between austenitic and martensitic phases increases with increasing carbon content, which implies the enhancement of the martensitic phase transition temperature (TMTM).
• The DOS peak at the Fermi level almost disappearing in the tetragonal phase near the Fermi level is the evidence of triggering martensitic transformation which due to the structural Jahn–Teller effect.
• The electron density difference shows the enhancement of bonding between Mn and carbon atoms with the distortion taken place.

The magnetic properties, structural stabilities and martensitic transformation of carbon doped Ni–Mn–Sn Heusler alloys are investigated by means of ab initio calculations in framework of the density functional theory. The results of calculations have shown that the martensitic transformation can be realized in all series of carbon doped Ni2Mn1.5Sn0.5 − xCx alloys with tetragonal ratio of 1.34, 1.40,1.42 and 1.44, respectively for x=0.125,0.25,0.375 and 0.5x=0.125,0.25,0.375 and 0.5. The DOS peak at the Fermi level almost disappearing in the tetragonal phase near the Fermi level is the evidence of triggering martensitic transformation which is due to the structural Jahn–Teller effect. We have also found that the difference between the austenitic and martensitic phases increases with increasing carbon content, which implies an enhancement of the martensitic phase transition temperature (TMTM). Besides, the electron density difference shows the enhancement of bonding between Mn and carbon atoms with the distortion taken place.