Effects of boron contents on magnetic properties of Fe-Co-B thin films

Effects of B on the magnetic properties and high frequency characteristics of the Fe₇Co₃ based thin films were investigated through the microstructural analysis. It was found that B addition was very effective in increasing anisotropy field and resistivity and in decreasing coercivity without much loss of saturation magnetization. These enhancements were shown to be strongly related to grain size, grain morphology and preferred orientations. As a result, a Fe₅₅Co₂₈B₁₇ film with small dispersion angle of ∼0.5° showed the ferromagnetic resonance frequency of 3.3 GHz and a linear effective permeability of ∼350 up to 2 GHz.