A series of (Fe0.67Co0.33)(1-x)Sm-x (0 <= x<0.25) thin films with thickness around 110 nm have been fabricated on silicon(111) substrates by magnetron co-sputtering at ambient condition with a 2.4 kA/m magnetic field applied in the film plane during deposition. With the Sm concentration increasing, FeCo grain size gradually decreases and FeCoSm film eventually becomes amorphous, while the isotropic magnetic property changes to in-plane uniaxial anisotropy as long as Sm is doped. The investigation of the angular dependence of coercivity and switching field indicates that the magnetization reversal mechanism of FeCoSm film is domain-wall depinning and coherent rotation when the applied field is close to the easy axis and hard axis, respectively. The anisotropy field and the resonance frequency of FeCoSm films can be tuned in the range of 15.0-109.5 kA/m and 5.2-11.8 GHz, respectively, by controlling the content of Sm, indicating that FeCoSm films have much potential in high-frequency applications. (C) 2012 Elsevier B.V. All rights reserved.