Influence of thickness, Si and SiO2/Si substrate interfaces upon magnetization dynamics in RF sputtered Fe3O4 thin films

Abstract

The effect of film thickness (90–220 nm), Si and SiO2/Si substrate interfaces upon structural, micro-structural and dynamic magnetic properties of RF sputtered Fe3O4 films are investigated. Structural and micro-structural studies have confirmed the polycrystalline Fe3O4 growth with a α-Fe2O3 minority phase. A systematic grain growth with thickness suggests the presence of anti-phase boundary (APB) and corresponding competing magnetic interactions. The absence of Verwey phase transition and lower effective magnetization of 283–359 emu/cm3 are attributed to the APBs. The influence of APBs and impurity states upon the magnetization dynamics has been investigated with co-planar waveguide ferromagnetic resonance spectroscopy from 9 to 33 GHz frequency range. A higher Gilbert damping of ∼0.016 is noted for Fe3O4/Si films as compared to the lower damping of ∼0.002–0.004 for Fe3O4/SiO2/Si interfaces. Further, inhomogeneity, intrinsic Gilbert damping and two-magnon scattering contributions to the damping parameter are evaluated and discussed.