Effects of C addition in Fe65Co35 and Fe9.5Co90.5 soft magnetic films

Fe65Co35 and Fe9.5Co90.5 thin films with carbon addition were deposited by reactive sputtering and investigated in terms of static and dynamic magnetic properties. The acetylene rate was adjusted in order to deposit nanocrystalline soft magnetic films, with a high saturation magnetization, a high resistivity, and a low coercivity. The transition of the crystalline structure to a nanocrystalline or amorphous arrangement-giving rise to soft magnetic properties-depended on the Fe/Co ratio and the C content. The lowest coercivity of 0.4 Oe was obtained for a Fe9.5Co90.5 film with 0.95% of C2H2, whereas a Fe65Co35 film with 0.75% of C2H2 exhibited a coercivity of 0.7 Oe. The microwave properties of the Fe65Co35 layers remained stable over this C2H2 content whereas the resonance frequency of the Fe9.5Co90.5 films decreased with the C2H2/Ar ratio. A difference in the manner that the carbon was incorporated, depending on the Fe/Co ratio, may explain the observed magnetic properties. (C) 2010 American Institute of Physics. [doi:10.1063/1.3356232]