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.