Magnetostriction and complex permeability of [Fe62Co19Ga19/Py]5/glass multilayered films

Abstract

[Fe62Co19Ga19(x)/Py(40–x)]5/glass multilayered films, where x=0, 5, 10, 15, 20nm, y=x(nm)/40(nm), and 0≤y≤1, were made by the magnetron sputtering method at room temperature. The total number of combined [Fe–Co–Ga/Py] unit-layers was five. The total film thickness (tf) was fixed at 200nm. We have performed two kinds of experiments on these films: (i) the saturation magnetostriction (λS) measurement, and (ii) the complex permeability (μ=μR–jμI) experiment to find the resonance frequency (fR) as a function of external magnetic field (HE). By definition, the microwave power absorption Pabs at ferromagnetic resonance (FMR) for a metallic conductor is written as Pabs=[(μR2+μI2)1/2+μI]1/2. We define the half-width of the absorption peak Δf as Δf ≣ ΔfS+ΔfA, where ΔfS and ΔfA are the symmetric and asymmetric parts in Δf. The degree of asymmetry, ΔfA/Δf, of each absorption peak is associated with the structural and/or magnetic inhomogeneity in the film. The main findings from this study are summarized as follows: (A) maximum λS occurs in the y=1 film, and as y increases, λS increases; (B) biasing field for magnetostriction decreases greatly by adding Py layers; (C) the magnetostriction sensitivity remains almost constant in the range 0.4<y ≦ 1; (D) μR increases, as y decreases. Thus, from this study we conclude that among all the [Fe62Co19Ga19/Py]5/glass films, the [Fe62Co19Ga19(30)/Py(10)]5/glass film should be the most suitable for applications in nano-magnetic switching devices.