Confined magnetic vortex motion from metal-organic frameworks derived Ni@C microspheres boosts electromagnetic wave energy dissipation

Abstract

Magnetic domain structure plays an important role in regulating the electromagnetic properties, which dominates the magnetic response behaviors. Herein, unique magnetic vortex domain is firstly obtained in the Ni nanoparticles (NPs) reduced from the Ni-based metal-organic frameworks (MOFs) precursor. Due to both the high symmetry spheres and boundary restriction of graphited carbon shell, confined magnetic vortex structure is generated in the nanoscale Ni core during the annealing process. Meanwhile, MOFs-derived Ni@C assembly powders construct special magnetic flux distribution and electron migration routes. MOFs-derived Ni@C microspheres exhibit outstanding electromagnetic (EM) wave absorption performance. The minimum reflection loss value of Ni@C–V microspheres with vortex domain can reach −54.6 ​dB at only 2.5 ​mm thickness, and the efficient absorption bandwidth up to 5.0 ​GHz at only 2.0 ​mm. Significantly, configuration evolution of magnetic vortex driven by the orientation and reversion of polarity core boosts EM wave energy dissipation. Magnetic coupling effect among neighboring Ni@C microspheres significantly enhances the magnetic reaction intensity. Graphitized carbon matrix and heterojunction Ni–C interfaces further offer the conduction loss and interfacial polarization. As result, MOFs-derived Ni@C–V powders display unique magnetic vortex, electronic migration network, and high-performance EM wave energy dissipation.