Local atomic structure of martensitic Ni2+xMn1-xGa:: An EXAFS study

The local atomic structure of Ni2+xMn1-xGa with 0 <= x <= 0.16 alloys was explored using Mn and Ga K-edge extended x-ray-absorption fine-structure (EXAFS) measurement. In order to study the atomic re-arrangements that occur upon martensitic transformation, room-temperature and low-temperature EXAFS were recorded. The changes occurring in the L2(1) unit cell and the bond lengths obtained from the analysis enables us to determine the modulation amplitudes over which the constituent atoms move giving rise to the shuffling of the atomic planes in the modulated structure. The EXAFS analysis also suggests the changes in hybridization of Ga-p and Ni-d orbitals associated with the local symmetry breaking upon undergoing martensitic transition.