Vortex-state Fe3O4 nanorings/graphene composites: composition-structure dual-regulation strategy for enhanced microwave absorption

Magnetic structure engineering and dielectric hybridization are a dual-regulation strategy to overcome the inherent constraints of magnetic materials, resulting in good impedance matching and improved microwave absorption properties. Herein, vortex-state Fe3O4 nanorings with controllable aspect ratio were integrated with lightweight graphene to systematically investigate the effects of Fe3O4-graphene component ratio and Fe3O4 nanorings aspect ratio on the electromagnetic parameters and microwave absorption properties. The particular ring-shaped Fe3O4 forms magnetic vortex structure that break Snoek’s limit, introducing broad natural resonance (0.8-10 GHz) and improved magnetic loss in the gigahertz range. Meanwhile, adjusting the aspect ratio of Fe3O4 nanorings and component of Fe3O4/graphene enables the tailored manipulation of interfacial polarization and dielectric dissipation mechanisms. The synergistic interplay between geometric anisotropy engineering and component optimization establishes an ideal impedance matching condition, culminating in exceptional microwave attenuation performance. For example, a remarkable reflection loss (RL) of -55.7 dB can be achieved with an ultrathin thickness of 1.6 mm, and an effective absorption bandwidth (RL≤-10 dB) of 5.66 GHz at only 2.0 mm. This work substantiates that morphological magnetic structure design combined with dielectric hybridization are viable strategies for developing high-performance magnetic microwave absorption absorbents in the gigahertz range.