Permeability and Magnetic Properties of Ferromagnetic NiFe/FeCoBSi Bilayers for High-Frequency Applications

In order to adjust the ferromagnetic resonance (FMR) frequency of thin NiFe films, ferromagnetic polycrystalline/amorphous NiFe/FeCoBSi bilayers using radio frequency magnetron sputtering were produced. Herein, the higher anisotropy field H_k of a ferromagnetic FeCoBSi was used to shift the FMR-frequency of the bilayer. Static and dynamic magnetic properties of the films were investigated by quasi-static magnetometry and by high frequency permeability measurements, respectively. The dynamic anisotropy field H_kdyn calculated from the FMR frequency of a single 100-nm NiFe-layer is shifted from mu₀H_kdyn=0.5 mT to mu₀H_kdyn=2.8 mT in a FeCoBSi(80 nm)/NiFe(20 nm) bilayer; whereas, the FMR frequency is congruently enhanced from 0.9 to 2.0 GHz. The permeability decreased from mu=2000 to mu=500. A linear dependence for the adjustment of the relevant magnetic parameters with NiFe:FeCoBSi ratio is demonstrated, opening the possibility to individually tailor magnetic properties of magnetic films for high-frequency applications