Undercooling growth and magnetic characterization of ferromagnetic shape memory alloy Ni2FeGa single crystals

Ni2FeGa single crystals have been grown in undercooling conditions provided by a glass-purification method. It has been found that trace amounts of γ phase embededin the single crystalline matrix preferentially orients in the 〈1 0 0〉 orientation along the growth direction. This γ phase generates directional residual stress and results in an anisotropic two-way shape memory effect. Large strains of −2.5% in the [0 0 1] and 1.5% in the [0 1 0] directions have been observed. This trace γ phase also improves the ductility of the material, thus the crystals could be plastically deformed at room temperature in the parent phase. The 〈1 1 0〉 and 〈1 1 1〉 orientations in Ni2FeGa alloy were identified as the easy and hard magnetization directions, respectively, in the parent phase by using low field M-T measurements.