Nano-Fe₃O₄ (magnetite nanoparticles) are excellent absorbing materials for electromagnetic (EM) waves, particularly microwaves, due to their magnetic loss and dielectric properties, often enhanced when combined with carbon materials (graphene, CNTs) or structured into composites (core-shell, hollow spheres) for better impedance matching, increased interfacial polarization, and lightweight designs, creating superior microwave absorbers for applications like stealth technology and EM shielding. 

Nano-Fe₃O₄ is highly effective, but its performance is dramatically boosted by combining it with carbon-based materials and designing complex architectures (hollow, core-shell) to optimize electromagnetic wave attenuation for practical applications.