Electronic Structures and Structural Transition Temperature of Shape Memory Alloys Ni_2+xMn_1-xGa

Abstract

The Heusler type alloys Ni2+xMn1-xGa are shape memory alloys and the phase transition temperature between a tetragonal and a cubic structure becomes higher with increasing Ni composition. To investigate the characteristic properties, the electronic structures of Ni2+xMn1-xGa were calculated for the cubic and the tetragonal structure. We found that the total energy difference between the cubic and the tetragonal structure becomes larger with increasing x, that is, the tetragonal structure becomes more stable. This tendency suggests the fact that the phase transition temperature becomes higher by substituting Mn with Ni in Ni2+xMn1-xGa.