Integration of ferromagnetic materials with electronic components represents a key solution to the enhancement of high frequency characteristics for recent miniaturized communication devices. In this study, Al element was introduced into FeCo binary alloy to form a ternary FeCoAl magnetic thin film by co‐sputtering technique followed by annealing in the presence of an external magnetic field. X‐ray diffraction results revealed that the FeCoAl films exhibited a solid solution microstructure of FeCo matrix with Al as the solute element. The saturation magnetization (Ms) of FeCoAl thin film still maintained a high value around 1780 emu/cm3. It was found that the FeCoAl system possessed a high permeability around 1000 and an uni‐axial anisotropic field (Hk) of 50 Oe. In addition, with the incorporation of Al element, the resonance frequency of the FeCoAl film reached 2.1 GHz. Hence, it is suggested that the FeCoAl magnetic thin film is a potential candidate for high frequency devices operated in GHz bands. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)