Microwave permeability of flake-shaped FeCuNbSiB particle composite with rotational orientation

Flake-shaped FeCuNbSiB particles were fabricated by ball milling the annealed ribbons. The composites of flake particles/paraffin wax were prepared with and without rotational orientation in an applied magnetic field. The complex permeability of the composites was measured in the frequency range of 0.1–18 GHz. The oriented composite showed higher permeability and resonance frequency compared with the unoriented one, while its value of (μ0−1)fr reached 128.9 GHz and exceeded the Snoek’s limit. Considering random and uniform distribution of the flake planes of the particles in the unoriented and oriented composites, respectively, the real part and imaginary part of the complex permeability of the composites were calculated using the Landau–Lifshitz–Gilbert equation and Bruggeman’s effective medium theory. The calculated results were basically in agreement with the experimental data.