Magnetic properties of metastable bcc phase in Fe64Ni36 alloy synthesized through polyol process

Abstract

The equilibrium FeNi alloy exhibits the bcc phase in a narrow composition less than 5 at.% Ni. Fe64Ni36 was obtained through instant chemical reduction employing polyol process and compared with Fe5Ni95 alloy. X-ray diffraction revealed bcc and fcc phases for the Fe-rich and Ni-rich FeNi compositions, respectively. The metastable bcc FeNi transformed to the fcc phase on annealing at 700 °C, whereas the Ni-rich alloy retained its fcc phase. Electron microscopic examination revealed spherical morphology for Fe64Ni36 alloy with an average size of 72 nm compared with flake-like morphology for the Fe5Ni95. The thermomagnetic analysis revealed a Curie temperature of 567 and 359 °C for the as-synthesized Fe and Ni-rich phases, respectively. An increase in Curie temperature by 30 °C was observed in both the compositions on annealing. Room temperature hysteresis loop measurements showed a saturation magnetization of 117 emu/g for bcc Fe64Ni36 alloy which increased to 165 emu/g for the fcc Fe64Ni36. The reaction kinetics involved in polyol process has enabled us to synthesis and investigate the magnetic properties of metastable bcc phase in the Fe64Ni36 composition.