Abstract:

Crystal structure, tetragonal distortion, magnetism, electronic structure and pressure response of Mn2NiAl were calculated by means of first\|principles method based on the density functional theory. The calculation results show the equilibrium structure of Mn₂NiAl in the cubic austenitic phase is the MnMnNiAl structure with Mn atoms occupying  A and B   non-equivalent positions. In the process of transform from a cubic to a tetragonal structure, Mn2NiAl alloys exhibit a stable martensitic phase in c/a≈1.24. In both the austenite and martensite phases, the contribution of Mn atoms  to the total moments for  Mn2NiAl is the largest, the magnetic moments of Mn(A) and Mn(B) atoms are inequality and antiparallel couple. The direct d-d exchange interactions between Mn(A) and Mn(B) atoms are weak because of the small overlap of d-projected DOS of Mn(A) and Mn(B) atoms nearby the Fermi level, but the intra-atomic interactions in Mn atoms are strong, this is the reason why the Mn2NiAl alloys show ferrimagnetism.

Key words: first-principles, electronic structure, ferrimagnetism, martensitic phase