High frequency characteristics of FeCoN thin films fabricated by sputtering at various (Ar+N2) gas flow rates

Abstract

FeCoN soft magnetic thin films with various nitrogen contents were fabricated by varying the gas flow rates of the argon and nitrogen gas mixture used during reactive rf magnetron sputtering. It was found that the resistivity of FeCoN film increased up to 211 μ cm with increasing nitrogen content. The film produced at the gas flow rate of 7 sccm exhibited the best soft magnetic properties with small coercivity and relatively large saturation magnetization. The microstructure of the films was examined by high-resolution transmission electron microscopy and α″ -FeCo phase with very high saturation magnetization was observed in the films. The high-frequency properties of the FeCoN thin films were experimentally characterized and theoretically examined. The Hoffmann's ripple theory was used to explain the permeability spectra for the films with strong magnetization dispersion. We found that the ripple effect is responsible for the large damping in the films, and those films with larger coercivities have stronger magnetization dispersion. With the gas flow rate of the argon and nitrogen gas mixture increasing from 0 to 15 sccm, the low-frequency permeability decreased from 680 to 245 and the ferromagnetic resonance frequency increased from 2.09 to 2.99 GHz. © 2006 American Institute of Physics.