Magnetic‐Field‐Annealing‐Induced Short‐Range Order in High‐Entropy Alloys for Enhanced Electromagnetic Response

The growing demand for microwave absorbers in 5G/6G technologies motivates processing routes that balance matching thickness, attenuation, and temperature response. Here, magnetic field annealing (MFA) is investigated in rGO-supported FeCoNi, FeCoNiCr, and FeCoNiCrCu compositionally complex alloys at 0, 0.5, and 0.95 T. Among the investigated FeCoNiCr samples, the 0.5 T sample exhibits a favorable combination of dielectric and magnetic responses. Reflection loss yields a minimum of -72.30 dB at 1.59 mm, and a maximum effective absorption bandwidth of 4.40 GHz. At 85°C, the maximum bandwidth is 4.08 GHz, corresponding to 92.7% retention of temperature-specific maxima. Local microscopy, field-associated atomistic modeling, and fixed-composition electronic-structure calculations support an interpretation of the electromagnetic response in terms of Co-centered chemical correlations. Finally, flexible antennas and strain sensors based on this composite demonstrate stable wearable responses, validating this SRO strategy from atomic design to device integration.