Vortex tuning magnetization configurations in porous Fe₃O₄ nanotube with wide microwave absorption frequency

The design and optimization of one-dimension (1D) magnetic material are of great importance for the energy conversion, storage and spin electron devices, which remain a huge challenge. Herein, 1D porous Fe₃O₄ nanotubes (NTs) have been fabricated via a combined process of electrospinning and calcination. In the electrospinning precursors, by regulating the content ratio between two types of polyvinyl pyrrolidone with different molecular weight, porous Fe₃O₄ NTs with vortex-domain configuration have been fabricated. Based on the unique 1D nanotube structure encapsulated with multi-domains, the composite Fe₃O₄ NTs exhibit high complex permeability (μʹ, μʺ) values, and hold both strong magnetic storage and dissipation capacity. Our Fe₃O₄ NTs exhibit excellent microwave absorption (MA) performance with the maximum reflection loss value of −57.1 dB and the efficient absorption bandwidth of 12.0 GHz. The generated magnetic vortices make the crucial contribution to the spin-wave resonance which improves the MA dissipation under high-frequency. Related magnetic flux line distribution and magnetic domain moment were confirmed by the electron holography and micro-magnetic simulation, respectively, providing the deep insight to the microwave absorption mechanism.