Hierarchical Dendrite-Like Magnetic Materials of Fe₃O₄, γ-Fe₂O₃, and Fe with High Performance of Microwave Absorption

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Iron-based microstructured or nanostructured materials, including Fe, γ-Fe 2 O 3, and Fe 3 O 4, are highly desirable for magnetic applications because of their high magnetization and a wide range of magnetic anisotropy. An important application of these materials is use as an electromagnetic wave absorber to absorb radar waves in the centimeter wave (2−18 GHz). Dendrite-like microstructures were achieved with the phase transformation from dendritic α-Fe 2 O 3 to Fe 3 O 4, Fe by partial and full reduction, and γ-Fe 2 O 3 by a reduction−oxidation process, while still preserving the dendritic morphology. The investigation of the magnetic properties and microwave absorbability reveals that the three hierarchical microstructures are typical ferromagnets and exhibit excellent microwave absorbability. In addition, this also confirms that the microwave absorption properties are ascribed to the dielectric loss for Fe and the combination of dielectric loss and magnetic loss for Fe 3 O 4 and γ-Fe 2 O 3 .