Synthesis and characterization of magnetic FeNi3 particles obtained by hydrazine reduction in aqueous solution

Ferromagnetic FeNi3 nanoparticles have been successfully synthesized via hydrazine reduction in aqueous solution at room temperature. The X-ray and transmission electron microscopy (TEM) analyses have shown that Fe2+ could be reduced into Fe with the assistance of Ni2+ in the solution. When the molar ratio of Fe2+ to Ni2+ is equal to 1/3, Ni2+ and Fe2+ were completely reduced into Fe and Ni, resulting in the formation of (FCC) FeNi3 phase. As-synthesized FeNi3 particles are of AuCu3 type structure and are nearly spherical-shaped with diameter about 50–200 nm. The particles are stable in the air and exhibit typical ferromagnetic properties. The saturation magnetization (Ms) reaches about 110 emu/g and coercivity is 100 Oe or so. The coercivity was decreased to 18 Oe after being quenched from above 550 to 25 °C.