高周波デバイス対応磁性ナノ粒子/ポリマー複合材料

摘要

Permeability and its upper-limitation frequency of superparamagnetic nanoparticle-based magneto-dielectric hybrid material were theoretically and experimentally investigated. The Landau-Lifshitz-Gilbert equation without any interaction between nanoparticles revealed that the blocking resonance frequency was able to exceed the ferromagnetic resonance frequency originating from the intrinsic magnetocrystalline anisotropy field by decreasing particle size, resulting in ultra-fast switching of superparamagnetic moment in the GHz range. The blocking resonance frequency for Fe nanoparticles could be increased to 130 GHz by reducing the particle size down to 1 nm. The experimental results for Fe_3O_4 and Fe nanoparticle assemblies supported the validity of our calculated results. Thus, superparamagnetic nanoparticle assemblies could be promising materials for high-frequency use over 10 GHz.