High frequency performance of laminated soft magnetic films (NiFe, FeAlN, and amorphous CoFeBSi) in external fields

Thin film multilayers of different compositions (NiFe, FeAlN, and amorphous CoFeSiB) were prepared by sputter deposition. The ultrahigh frequency performance was studied using rf fields perpendicular to the in-plane easy axis. By applying external bias fields either along or perpendicular to the easy axis (perpendicular to the rf field excitation), the cutoff frequency of the different alloys can be shifted significantly to higher frequencies (>1 GHz) according to theory. On the other hand, it is possible from these measurements to identify different phenomenological damping of the material systems due to structural effects. Although FeAlN exhibits the highest saturation magnetization compared to NiFe and CoFeBSi, it shows a higher damping which is explained by nonideal structure.