Shape-optimized ferromagnetic particles with maximum theoretical microwave susceptibility

摘要: This paper uses a shape-dependent form of Snoek's relation to show that the geometry soft ferromagnetic objects can be chosen maximize their linear susceptibilities at microwave frequencies. Composites made with such fill critical void in frequency range (1 20 GHz) where thin films or spherical do not yield maximum susceptibility allowed by relation. The relatively small intrinsic anisotropies materials necessitate use shape anisotropy susceptibility. Our results used determine optimum and theoretical achievable given frequency. enhancement factor 10-100 obtained 1-20 GHz (0.3-7 for low loss applications) using oblate spheroids aspect ratios between 10 1000. Keeping thickness below skin depth will require lateral dimensions /spl sim/1-1000 mu/m. Fabrication measurements are discussed companion paper.