Relation Between High-Frequency Properties and Direction of Anisotropy Magnetic Field in Magnetic Thin Film for RF Inductor Applications

A relation between high-frequency properties, and angle θ of the easy axis in soft magnetic film and ac applied field was investigated in order to fabricate the film for RF spiral inductor without a localized EMI (Electro-Magnetic Interference). This relationship was measured using a soft CoFeSiO/SiO₂ granular multilayer magnetic thin film and simulated by using LLG (Landau-Lifshitz-Gilbert) micromagnetic simulator. The measured and calculated frequency dependence of the film´s complex relative permeability, μ_r^´ and μ_r^´´, compared well with 10% mean error. The real part of complex relative permeability μ_r^´ was dependent on approximately sin²θ . The ferromagnetic resonance (FMR) frequency, f_r, and the FMR half-width, Δf_r were not dependent on the angle, θ . They were estimated to be 2.54 GHz and 0.3 GHz, respectively. These results are significant for the design of various magnetic thin film spiral inductors in RF integrated circuits without localized EMI.