| Summary: | Cobalt ferrite nanoparticles of different stoichiometries synthesized by a sol–gel autocombustion method were used as a starting material to obtain high-moment Fe<sub>50</sub>Co<sub>50</sub> and Fe<sub>66</sub>Co<sub>34</sub> metal nanoparticles by topochemical hydrogen reduction. Structural and magnetic investigations confirmed the formation of FeCo nanoparticles with crystallite sizes of about 30 nm and magnetization at 0.5 T of ~265 Am<sup>2</sup>/kg (0 K), which was larger than the expected bulk value, likely because of the incorporation in the body-centered cubic (bcc) FeCo structure of the residual C atoms present on the surface of the oxide particles. Temperature-dependent magnetization measurements in the H<sub>2</sub> atmosphere were also performed to investigate in detail the reduction mechanism and the effect of an external magnetic field on the process efficiency.
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