Role of antisite disorder in the martensitic transition of Ni sub(2-x) Mn sub(1+x) Ga

Abstract

A systematic investigation of the structure and local structure of Ni sub(2-x) Mn sub(1+x) Ga alloys 0 less than or equal to x less than or equal to 1 reveals antisite disorder to be a possible reason for higher martensitic transformation temperature of Mn sub(2) NiGa as compared to Ni sub(2) MnGa. The antisite disorder between the Y and Z sublattices of the X sub(2) YZ Heusler structure results in segregation of Mn sub(3) Ga type defect phase and a Ni-rich Heulser phase with a higher e/a ratio. This Ni-rich Heusler phase appears to be responsible for the higher martensitic transformation temperature of the Mn sub(2) NiGa type Heusler alloys.