Effect of induced uniaxial magnetic anisotropy on ferromagnetic resonance frequency of Fe–Co alloy nanoparticle/polystyrene nanocomposite

An Fe–Co nanoparticle assembly with uniaxial nanostructure was successfully obtained as a nanocomposite with polystyrene, which was polymerized in a magnetic field, Hfix (50 kOe), from a mixture of the Fe–Co nanoparticles and styrene monomer. The easy axis of magnetization was parallel to Hfix and the uniaxial magnetic anisotropy field of the nanocomposite was estimated to be 2.5 kOe. The ferromagnetic resonance frequency of the nanocomposite reached 6.8 GHz, which was larger than that of the nanocomposite prepared without Hfix.