STRUCTURE AND MAGNETIC PROPERTIES OF (Fe-Cu)@C NANOCOMPOSITES

Nanocomposites (Fe - Cu)@C with a metal core-carbon shell structure were obtained using the gas condensation method. An analysis of X-ray structural data and electron microscopic images has been carried out, which shows that the core of the composites is represented by a nonequilibrium Cu-Fe solid solution with a face-centered cubic (FCC) structure. The carbon content in the composites ranges from 19 to 24 wt %, most of the carbon forms the shell, and some carbon is dissolved in the core. The average particle size (including the shell), determined from the specific surface area, ranges from 6 to 9nm. Over the entire studied range of iron concentrations - from 33 to 83 at %, the composites exhibit ferromagnetic behavior in the temperature range from 2K to (300 - 600)K (depending on the composition). The temperature dependences of the magnetic susceptibility are interpreted within the framework of a model assuming the presence of carbon in the core of the particles. Presumably, it is the carbon dissolved in the core that stabilizes the FCC phase in the Cu- Fe system even with a high iron content (83 at % ).