Magnetic and electrical transport properties of Heusler shape-memory alloy Ni₂FeGa

Magnetic shape-memory materials have attracted considerable attention owing to their stability, magnetic field-induced controllability, and superior thermo-mechanical performance. These properties render them exciting application potential in robotics, electro-mechanical systems, aerospace, and medical devices. In this talk, we will report structural, magnetic, and electronic properties of a Heusler ferromagnetic shape memory alloy Ni₂FeGa. We fabricate the alloy ribbons by using a melt spinning process. The alloy possesses a well-defined γ-phase (austenite) structure at room temperature, inferred from the x-ray diffraction measurements. Moreover, the alloy ribbons undergo a first-order austenite-to-martensitic phase transition near 150 K, as indicated by the temperature-dependent electronic and magnetization measurements. We observe a 8% reduction in resistivity as the alloy ribbon transforms from the magnetically hard martensitic to the soft austenitic phase. This resistance change is large for a shape-memory alloy. We also record a negative magnetoresistance (MR) of the alloy ribbons and the MR shows a structure-phase dependence. These electronic and magnetic properties of the Ni₂FeGa alloy grants it great potential for spintronic applications.