Ab initio-based investigation of phase transition path and magnetism of Ni–Mn–In alloys with excess Ni or Mn

Abstract

Herein, we have revealed the phase transition path and magnetic properties of Ni–Mn–In alloys with excess Ni or Mn (Ni24+xMn12In12-x, Ni24+xMn12-xIn12 and Ni24Mn12+xIn12-x) by using ab initio calculations. It is demonstrated that excess Ni atoms prefer to be adjacent to each other for the Ni24+xMn12In12-x alloys, whereas excess Ni (Mn) atoms tend to keep away from each other for the Ni24+xMn12-xIn12 and Ni24Mn12+xIn12-x alloys. The variation of the lattice constants, which are dominated by the atomic radius, are basically the same for the three alloy systems. Excess-Ni decreases the stability of the ferromagnetic austenite (FA) as well as the 6M and NM martensites. Meanwhile, the Curie temperature (TC) is reduced but the martensitic transformation temperature (TM) is increased due to the presence of excess-Ni. In comparison, excess-Mn destabilizes the FA phase, but stabilizes the 6M and NM phases. Excess-Mn has a similar impact on the increase of TM as that of excess-Ni, but has a weak effect on TC, but increases TM. The critical composition of the martensitic transformation and martensitic transition path are determined. The highest total magnetic moment of the FA phase appears with Mn-excess compositions whilst the smallest total magnetic moment is found with Ni-excess compositions. The changes of the total magnetic moments for the 6M and NM phases demonstrate an opposite trend to that of FA phase. The above results are expected to provide information for the prediction of phase diagram and magnetic properties of Ni–Mn–In alloys.