First-principle investigations of the magnetic properties and possible martensitic transformation in Ni2MnX (X=Al, Ga, In, Si, Ge and Sn)

• Both austenitic and martensitic Ni2MnX alloys are found to be ferromagnets.
• The energy difference between the martensitic and austenitic phases is negligible.
• The total moment in martensitic phase is close to corresponding to austenitic phase.

The magnetic and electronic properties of Ni2MnX (X=Al, Ga, In, Si, Ge and Sn) Heusler alloys have been studied by using the first-principle projector augmented wave potential within the generalized gradient approximation. The possible non-modulated martensitic transformation in these six alloys has been investigated. Both austenitic and martensitic Ni2MnX (X=Al, Ga, In, Si, Ge and Sn) Heusler alloys are found to be ferromagnets. In martensitic phase, the energies minimum occurs at c/a=0.99 for Ni2MnX (X=Al, In, Ge and Sn), and the energy minimum occurs at c/a=1.02 for Ni2MnSi. But there is a negligible energy difference ΔE (<6 meV/cell) between the austenitic and martensitic phases for each alloy. Meanwhile, around c/a=1, an anomaly is observed in the E-c/a curve, which is related to a very slightly tetragonal distortion trend in Ni2MnX (X=Al, In, Si, Ge and Sn). The energy difference ΔE between the austenitic and martensitic phases for Ni2MnGa is as large as 99 meV/cell, so it is more likely to realize martensitic transformation in it.