Microstructure and low-temperature phase transition in Ni2FeGa Heusler alloy

The microstructure features and structural phase transition in the Ni2FeGa alloy has been systematically investigated by means of transmission electron microscopy (TEM). A number of ordered states have been observed at room temperature; certain short-range orders are found to be in metastable states which are temperature sensitive and become invisible when annealed. In situ cooling TEM observations revealed evident structural changes along with the martensitic transition with Tc∼145 K. Low-temperature microstructure domains, superstructures and variations of monoclinic distortion have been analyzed in detail.