Abstract
In this paper, we investigate the high frequency performance of Co90Zr10/SiO2/Co90Zr10 trilayers. It is demonstrated that the in-plane isotropic microwave performance is theoretically derived from the solution of the Landau-Lifshitz-Gilbert equation and experimentally achieved in that sandwich structured film. The valuable isotropic behavior comes from the superposition of two uncouple ferromagnetic layers in which the uniaxial magnetic anisotropic fields are equivalent but mutually orthogonal. Moreover, the isotropic microwave performance can be tuned to higher resonance frequency up to 5.3 GHz by employing the oblique deposition technique. It offers a convenient and effective way to achieve an unusual in-plane isotropic microwave performance with high permeability in GHz, holding promising applications for the magnetic devices in the high frequency information technology.
Highlights
Soft magnetic materials with isotropic high permeability (IHP) at working frequency are crucial components in modern information technology because of their extensive applications to improve the performance of magnetic devices such as micro-transformers, planar inductors and core materials of writing head[1,2,3]
As the frequency response of the permeability is almost flat up to a rolloff frequency, associated with ferromagnetic resonance, when a microwave magnetic field h is applied perpendicular to the in-plane uniaxial magnetic anisotropy (IPUMA) field HK, the resonance frequency fr and initial permeability μin of the magnetic thin films can be adjusted by HK as
We report the achievement of an in-plane IHP with resonance frequency higher than 5 GHz in a convenient FM1/NM/FM2 (FNF) film, in which two ferromagnetic layers (FMi, i = 1, 2) are decoupled by a non-ferromagnetic interlayer (NM)
Summary
Considering a microwave magnetic field h applied in the plane of the FNF film as shown, the complex susceptibility of the film comes from weighted average of complex susceptibility of FM1 and FM2, written as χ′(ω, θ) = ∑ pi χ′i, i=1. The microwave susceptibility of precession of magnetization, which can be described by LLG equation[47], so the susceptibility of FMi layer (χ′i and χ′′i) can be derived from LLG equation, and given by χ′i (ω, θ). As μ′ = 1 + χ′(ω, θ) and μ′′ = χ′′(ω, θ), the complex permeability is generally angular dependent. An angular independent complex permeability of the FNF film can be derived as μ′ (ω).
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