Broad UHF ferromagnetic resonance of iron rich-aluminum pulsed laser deposited thin films

The magnetic susceptibility of Fe–Al off-normal pulsed laser deposited thin films was measured at ultra high frequencies, UHF. Different Fe1−x–Alx films from pure Fe to x=0.2 Al were prepared. The films were ≈40nm thick and non-crystalline peaks were detected by the X-ray diffractometry studies. The magnetization of the films remained between 2.0 and 1.8T for composition less than or equal to 20% Al. A magnetic anisotropy, from Hk≈18Oe for pure Fe to Hk≈130Oe for 20% Al was measured. These samples exhibited a well-defined ferromagnetic resonance at frequencies between ≈2.0GHz and 3.8GHz depending on composition. The broad resonance peaks had a width, at half maximum, wh, in the interval from 2.5GHz to 4.0GHz depending on Al content. After fitting the magnetic hysteresis loops using a simple distribution of anisotropy values, we used the Landau–Lifshitz–Gilbert equation to fit the UHF magnetic susceptibility. From this last fit we obtained a high damping coefficient value (≈4 times higher than that corresponding to Co or CoFe films), explaining this broad ferromagnetic resonance of these Fe1−x–Alx films.