Phase Stability, Magnetic Properties, and Martensitic Transformation of Ni2-xMn1+x+ySn1-y Heusler Alloy with Excess Mn by First-Principles Calculations

The phase stability, magnetic properties, martensitic transformation, and electronic properties of the Ni2-xMn1+x+ySn1-y system with excess Mn have been systematically investigated by the first-principles calculations. Results indicate that the excess Mn atoms will directly occupy the sublattices of Ni (Mn-Ni) or Sn (Mn-Sn). The formation energy (E-f) of the austenite has a relationship with the Mn content: E-f = 135.27(1 + x + y) - 293.01, that is, the phase stability of the austenite decreases gradually with the increase in Mn content. According to the results of the formation energy of austenite, there is an antiparallel arrangement of the magnetic moment between the excess and normal Mn atoms in the Ni2-xMn1+x+ySn1-y (x = 0 or y = 0) system, while the magnetic moment direction of the normal Mn atoms arranges antiparallel to that of Mn-Ni atoms and parallel to that of Mn-Sn atoms in the Ni2-xMn1+x+ySn1-y (x, y not equal 0) system. The martensitic transformation occurs in some Ni2-xMn1+x+ySn1-y (x, y not equal 0) alloys with large magnetic moments of ferrimagnetic austenite. Besides, the valence electrons tend to distribute around the Ni or Mn-Ni atoms and mainly bond with the normal Mn atoms. The results of this work can lay a theoretical foundation for further development of the Ni2-xMn1+x+ySn1-y system as the potential ferromagnetic shape memory alloys.

Automated summary

The Ni2-xMn1+x+ySn1-y system with excess Mn was systematically investigated using first-principles calculations. The results showed that the excess Mn atoms occupied the sublattices of Ni or Sn, and the phase stability of the austenite decreased with an increase in Mn content. The alloys with large magnetic moments of ferrimagnetic austenite underwent martensitic transformation. Valence electrons mainly distributed around Ni or Mn-Ni atoms and bonded with normal Mn atoms. The findings provide a theoretical foundation for further development of the Ni2-xMn1+x+ySn1-y system as potential ferromagnetic shape memory alloys.