CoFe2O4/Fe magnetic nanocomposite: exchange coupling behavior and microwave absorbing property

In this research, a CoFe2O4/Fe magnetic nanocomposite was successfully produced through mechanical alloying. The effects of different Fe concentrations (10, 30, and 50 wt %) and milling time (1, 3, 5, and 10 h) on the characteristics of the nanocomposite samples were systematically investigated. Single-phase CoFe2O4 nanoparticles were produced with a mean particle size of 60 nm and a saturation magnetization of 76 emu/g. The FESEM and HRTEM images confirm the heterostructure and particle size reduction of the CoFe2O4/30 wt% Fe nanocomposite after milling for 5 h. Also, the STEM-EDX signals of this nanocomposite sample revealed a uniform elemental distribution after 5 h of milling. The single-phase-like hysteresis loop and switching field distribution curves of 3-h milled nanocomposites containing 10 and 30 wt% Fe, revealed exchange coupling in the nanocomposite samples. This result was confirmed by simultaneous enhancements of the maximum energy product (BH)max and the remnant magnetization/saturation magnetization ratio (Mr/Ms). The (BH)max value of the CoFe2O4/10 wt% Fe nanocomposite after 3 h milling was 2.7 MGOe, which was about 1.8 times higher than that of single-phase CoFe2O4 nanoparticles. An epoxy-based nanocomposite fabricated with CoFe2O4/Fe segments exhibited magnetic losses in the X-band frequency range. The maximum reflection loss (−27 dB at 11.2 GHz frequency) for the CoFe2O4/30 wt% Fe nanocomposite milled for 10 h was 8 times greater than that of pure CoFe2O4 nanoparticles.