Enhanced Soft Magnetic Properties in N-Doped Amorphous FeCo Thin Film

Sputtered FeCoNx thin films with various nitrogen fractions are investigated in the quest of low lossy, soft magnetic thin films (SMFs) for high-frequency inductor core. 100 nm thick FeCoNx films were deposited in N2 + Ar environment (5 m torr) with increasing N2 volume percent, $x$ % = N2/(Ar + N2), up to 30%. While FeCo thin film is isotropic, the incorporation of nitrogen in the film exhibits a well-defined uniaxial magnetic anisotropy (UMA) as a result of reduced stress in the FeCoNx films. FeCoN17.5 thin film with UMA shows superior all-round soft magnetic properties (saturation flux density ~1.7 T, coercivity ~7.8 Oe, real permeability ~381.7 and resistivity $\sim 201 ~\mu \Omega \cdot $ cm). The study of the dynamic magnetic properties of FeCoNx ( ${x}$ = 15%, 17.5%, and 19%) films reveal two ferromagnetic resonance (FMR) peaks. Double resonance peaks in films with a high concentration of nitrogen might be related to FeCo and Fe-N multiphase in the films. Furthermore, the evolution of the real $\left ({\mu ^{\prime } }\right)$ and imaginary ( $\mu ^{\prime \prime }$ ) part of the permeability spectra in the presence of dc magnetic bias field is also examined.