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 similar to 0.5degrees showed the ferromagnetic resonance frequency of 3.3 GHz and a linear effective permeability of similar to350 up to 2 GHz.