Microwave complex permeability of Fe3O4 nanoflake composites with and without magnetic field-induced rotational orientation

Magnetite (Fe₃O₄) nanoflakes with widths of 100-200 nm and thicknesses of 10-80 nm were prepared by a hydrothermal synthesis method. Fe₃O₄ nanoflake composites with and without magnetic field-induced rotational orientation of flake planes of Fe₃O ₄ nanoflakes in paraffin binder were fabricated using 35 wt. Fe ₃O₄ nanoflakes. The rotationally oriented composite showed higher permeability and resonance frequency than the nonoriented one, and its value of (μ 0 - 1) f r reached 214.8 GHz and exceeded the Snoeks limit. Considering a uniform and a random distribution of flake planes of Fe ₃O₄ nanoflakes in the oriented and nonoriented composites, respectively, the complex permeability of both composites was calculated using the Landau-Lifshitz-Gilbert equation and the Bruggemans effective medium theory in the 2-18 GHz microwave frequency range.