Effect of annealing temperature on the magnetic and microwave absorption of FeNi alloy

FeNi alloys were synthesized by hydrothermal reduction method. The effects of different annealing temperatures on magnetic properties and microwave absorption properties were investigated. As the annealing temperature increases from 150 °C to 700 °C, the saturation magnetization of FeNi alloys increases from 83.61 to 103.24 A·m2·kg−1, and the coercivity decreases from 12.18 to 0.68 kA·m−1. FeNi alloy changes from semi-hard magnetic behavior to typical soft magnetic behavior. The optimum reflection loss (RL) of the FeNi alloy (700 °C) is −28.36 dB at 3.84 GHz. Especially, the effective absorption bandwidth (RL < −10 dB) of FeNi alloy (700 °C) is up to 3.26 GHz. These results suggest that the FeNi alloys could be a desirable S-band operational microwave absorber.