Structural and Magnetic Studies of CoFe2O4 Ferrite, CoFe2O4/CoFe2 Nanocomposites and CoFe2 Nano-alloy

Nanoferrite of CoFe2O4 was synthesized using the glycol-thermal method at 200 ∘C for 6 h. The nanocomposites and nano-alloy were produced by the reduction of the ferrite using different amounts of activated charcoal at 900 ∘C for 3 h in high-purity flowing argon atmosphere. Complete reduction yields the nano-alloy phase while partial reduction produces the nanocomposites. XRD measurements of the nanoferrite showed a single-phase spinel structure with an average crystallite size of about 10 nm. The CoFe2 nano-alloy was obtained at an activated charcoal molar ratio of nC=6. The HRTEM of all the reduced samples showed clear differences. 57Fe Mössbauer spectra measurements of the reduced samples showed the transformation of the spinel structure to the composite and alloy phase. Mössbauer fits showed that Fe 3+ was reduced to Fe 2+ with lower magnetic hyperfine fields observed in the reduced samples. Magnetization measurements for reduced samples show significant enhancement. The coercivity of the fully reduced samples of the nanoferrite was observed to be less dependent on temperature.