Characterization of FeCo particles synthesized via co-precipitation, particle growth using flux treatment and reduction in hydrogen gas

•FeCo particles synthesized via Fe/Co:1/1, flux treated, and reduction.•Spherical or slightly elongated shape with size of approximately 30-200 nm.•Composition with Fe60Co40 determined from D-spacing of (110) peak.•Coercive force of 90 kA/m and saturation magnetization of 150 Am2/kg.

The possibility of high coercive force in FeCo particles was examined focusing on distortion introduced in the particles. The particles were synthesized via co-precipitation of Fe and Co ions, heat-treatment in potassium bromide flux for particle growth, and reduction using hydrogen gas. The particle shape was spherical or a slightly elongated with the size of approximately 30-200 nm, and the composition with approximately Fe60Co40 was determined from the d-spacing of (110) peak. The coercive force of approximately 90 kA/m was obtained in particles with the saturation magnetization of approximately 150 Am2/kg. The coercive force was higher than those in reported FeCo particles with same level of saturation magnetization. As one of the reason of high coercive force, we expected the possibility of occurrence of magnetic anisotropy based on the anisotropic distortion generated between FeCo alloy and surface oxides in a slightly elongated particles.