Magnetic and microwave absorption properties of core/shell FeCo-based nanocomposites synthesized by a simple wet chemical method

FeCoB nanocomposites coated with FeCo-oxide layers were synthesized by a simple wet chemical method. Postannealing treatment was carried out from 400 °C to 600 °C. TEM observations show that the FeCoB particles have an average diameter of several tens of nanometer. The FeCoB nanoparticles are coated with 3 nm thick FeCo-oxide layers, exhibiting good core/shell structure. X-ray diffraction analysis demonstrates that the samples have bcc FeCo structure. A maximum saturation magnetization of 173.9 emu/g and a minimum coercivity of 169.1 Oe are obtained. Microwave absorption measurements show that the as-synthesized FeCoB nanocomposites exhibit a minimum reflection loss (RL) of -29.3 dB at the frequency of 13.2 GHz. Bandwidths of 4.1 GHz (11.0-15.1 GHz) for an RL of -20 dB and 7.4 GHz (9.1-16.5 GHz) for an RL of -10 dB are estimated, respectively.