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Carbon-coated Fe and Co nanocapsules have been synthesized by a chemical vapor condensation process using carbon monoxide as carrier gas. The characterization and magnetic properties of carbon-coated Fe and Co nanocapsules are investigated and compared. The core/shell structure of the Fe(C) nanocapsules is similar to that of the Co(C) nanocapsules, consisting of an amorphous shell and a metallic core. The phases of the Co(C) nanocapsules are composed of f.c.c.-Co, h.c.p.-Co and cobalt carbides regardless of the decomposition temperature and the CO gas flow rate. The phases of the Fe(C) nanocapsules change with changing decomposition temperature and CO gas flow rate. The majority phases of the Fe(C) nanocapsules are alpha-Fe and Fe3C when the decomposition temperature is between 500 and 1000 degreesC, but for 700 degreesC only Fe3C exists alpha-Fe, gamma-Fe and Fe3C phases coexist after preparation at 1100 degreesC. The saturation magnetization of the Co(C) nanocapsules increases with increasing decomposition temperature, while that of the Fe(C) nanocapsules is less dependent on the phases formed. The cobalt nanocapsules reach 90% of the value of the saturation magnetization of bulk cobalt, while the iron nanocapsules obtained at 400 and 1100 degreesC reach 75 and 33 % of the saturation magnetization of bulk iron. The carbon-coated Fe and Co nanocapsules are shown to be ferromagnetic with a ratio of the remnant magnetization to saturation magnetization M-r/M-s of 0.3-0.4. (C) 2003 Elsevier B.V. All rights reserved.