Ferromagnetic resonance properties of Fe_81-xNi _xGa₁₉/Si(1 0 0) and Fe_81-yNi _yGa₁₉/glass films

Two series of Fe_81-xNi_xGa ₁₉/Si(1 0 0) and Fe_81-yNi_yGa ₁₉/glass films, where x or y = 0-26, were made by the magnetron sputtering method. The film thickness (t_f) was fixed at 100 nm. We have performed three kinds of experiments on these films: (i) the saturation magnetostriction (λ_S) measurement; (ii) the easy-axis and hard-axis magnetic hysteresis loop measurements; and (iii) the ferromagnetic resonance (FMR) experiment to find the resonance field (H_R) with an X-band cavity tuned at f_R = 9.6 GHz. The natural resonance frequency, f_FMR, of the Kittel mode at zero external field (H = 0) is defined as f_FMR ≒ ν[H_K4πM_S]^1/2, where γ = 2πν is the gyromagnetic ratio, H_K and 4πM_S are the uniaxial anisotropy field and saturation magnetization, and H_K << 4πM_S. The Gilbert damping constant, α, is calculated from the formula, α = [ν(ΔH)_S]/(2f_R), where (ΔH)_exp = (ΔH)_S + (ΔH)_A, (ΔH)_exp is the half-width of the absorption peak around the resonance field H_R, (ΔH)_S is the symmetric part of (ΔH)_exp, and (ΔH)_A is the asymmetric part. The degree of asymmetry, (ΔH)_A/(ΔH)_exp, is associated with the structural and/or magnetic inhomogeneities in the film. The main findings of this study are as follows: (A) f_FMR tends to decrease, as x or y increases; (B) α decreases from 0.052 to 0.020 and then increases from 0.020 to 0.050, as x increases, and α decreases from 0.060 to 0.013 in general, as y increases; and (C) λ_S reaches a local maximum when x = 22. We conclude that the Fe₅₉Ni₂₂Ga ₁₉/glass film should be the most suitable for application in magneto-electric microwave devices.