Microstructural, Magnetic and Electrical Properties of Ni2FeGa Heusler Alloys

Ni2FeGa polycrystalline alloys are synthesized by arc melting into single phase beta structure and two phase mixture of gamma-phase (fcc) and austenite (L-21). Annealing improves atomic ordering and beta transforms to L-21 ordered structure. Effect of alloy composition and processing condition on different phase formation, microstructural, magnetic and electrical properties are discussed. The alloy undergoes first order austenite to martensitic phase transformation at 225 K with low hysteresis of 10 K. The resistivity exhibits a jump upon martensite transformation. This increase in resistivity is being attributed to the change in effective mass of electron upon martensite transformation. The temperature dependent resistivity curve for both austenite and martensite varies linearly with alpha T suggesting strong electron-phonon scattering. The slope of temperature dependent resistivity curve is higher in case of austenite than that of martensite and is attributed to the increasing role of electron-phonon scattering at high temperature.