Abstract: Fe_0.13[Co₂₀Ni₈₀]_0.87 alloy fine fibers were prepared by organic-gel thermal reduction process using citric acid and metal salts as raw materials. The structure and morphologies of the gel precursors and fibers derived from thermal reduction of these precursors were characterized by FTIR, XRD, TG/DSC and SEM. The magnetic properties for the as-prepared alloy fibers were examined by vibrating sample magnetometer(VSM). The results show that Fe_0.13[Co₂₀Ni₈₀]_0.87 alloy fibers are characterized with thin diameters between 0.3 and 2.0 μm, with high aspect (length over diameter) ratio, dense and smooth surfaces. The crystalline size of the alloy fibers are mainly influenced by the thermal reduction temperature and are in the range of 20 to 50 nm with a corresponding reduction temperature range of 300 to 700 ℃. The magnetic properties of the alloy fibers are largely affected by the carbon content and crystalline sizes of the alloy fibers. With increasing thermal reduction temperature, the coercivity decreases while the saturation magnetisation value of the alloy fibers dramatically increases at lower reduction temperatures. The alloy fibers prepared at reduction temperature of 700 ℃ have a saturation magnetisation value of 120 A∙m²/kg and a coercivity value of  10.4 kA/m, respectively.

Key words: organic gel-thermal reduction method; nanocrystalline; Fe_0.13[Co₂₀Ni₈₀]_0.87 alloy fibers; ferromagnetic properties