Broadband microwave absorption enhancement in FeCoNiCrMn HEAs through optimal MgO incorporation

High-entropy alloys (HEAs) demonstrate exceptional potential as electromagnetic wave absorbers owing to their tunable electromagnetic properties and compositional adaptability. Here, we investigate FeCoNiCrX (X = Cu, Mn, Mo, Al, Y) high-entropy alloys synthesized by vacuum induction melting-gas atomization. The FeCoNiCrMn system shows optimal microwave absorption performance, achieving a minimum reflection loss (RL) of −37.39 dB at 16.32 GHz (5.5 mm thickness) and an effective absorption bandwidth (EAB < −10 dB) of 1.52 GHz (16.48–18 GHz) at 5 mm. Surface engineering through MgO incorporation (1.0 wt%) further improves impedance matching, yielding a composite with RL min = -35.13 dB at 13.76 GHz (2 mm thickness) and 84 % broader EAB (2.8 GHz, 13.52–16.32 GHz) compared to pristine HEAs. The enhancement results from optimized dielectric-magnetic coupling and interfacial polarization, providing a strategic approach for designing thickness-adaptive microwave absorbers.