Magneto alignment of Ni _0.5 Co _0.5 Fe ₂ O ₄ @graphene flakes for highly efficient low-frequency microwave absorption

Abstract The increasing deployment of low-frequency microwaves (L-band: 1–2 GHz, S-band: 2–4 GHz) in civilian and military applications has significantly intensified electromagnetic radiation pollution, posing growing risks to public health and the reliability of high-precision electronic systems. However, the development of highly efficient microwave absorbers for these low-frequency ranges remains a significant challenge. In this study, structurally controlled Ni _0.5 Co _0.5 Fe ₂ O ₄ @graphene/polyurethane composite films were fabricated via a magnetic field-induced alignment strategy. The resulting flexible composites exhibit enhanced complex permeability, high complex permittivity, and pronounced dielectric/magnetic loss capabilities, along with improved impedance matching at relatively low thicknesses and frequencies. As a result, when the film thickness is only 3.5 mm, magnetic field-induced structural ordering shifts the reflection loss ( RL ) peak from 2.67 GHz to 1.75 GHz and significantly improves the minimum RL from −32 dB to −55 dB, achieving an effective absorption bandwidth of 0.95 GHz. This work demonstrates that magnetic field regulation enables precise control over electromagnetic response, effectively tailoring the absorption characteristics toward lower frequencies while substantially enhancing overall performance. These findings provide a promising and scalable strategy for the design and fabrication of high-performance low-frequency microwave absorbing materials.