Abstract
AbstractThe complex permeability of Cu‐doped nickel‐zinc polycrystalline ferrites is strongly dependent on microstructure, particularly, on relative density () and average grain size (). In this study, a mathematical model, able to fit the measured magnetic permeability spectra from 106 to 109 Hz, is proposed and validated for a width range of average grain sizes (3.40–23.15 μm) and relative densities (0.83–0.96). To the authors’ knowledge, domain‐wall motion and spin rotation contributions to magnetic permeability have been integrated jointly with the microstructure for the first time in the proposed model, highlighting the relative influence of each magnetizing mechanism and microstructure on the magnetic permeability at different angular frequencies.
Highlights
Ferrites are considered nowadays the leading electromagnetic interference absorbers (EMI), due to its good chemical stability, high resistivity, and excellent electromagnetic properties and cost effective
In polycrystalline ferrites, two kinds of magnetizing mechanisms contribute to magnetic permeability: spin rotation and domain-wall motion,[4,5,6,7,13,16,17,18,19] and, usually, the higher the angular frequency of the magnetic field, the lower the influence of the domain-wall motion mechanism.[13,14,16,18]
As shown in this figure, the real part of the magnetic complex permeability decreases with frequency while peaks in the imaginary part, highlighting the strong influence of this second with frequency dispersion
Summary
Ferrites are considered nowadays the leading electromagnetic interference absorbers (EMI), due to its good chemical stability, high resistivity, and excellent electromagnetic properties and cost effective. Ferrites used as EMI applications are classified into two generic types: NiZn and MnZn ferrites. The Cu-doped NiZn ferrites are the most widely used because of their large range of applications in the higher MHz angular frequencies, for example, communication components, microwave devices, multilayer chip inductors, energy storage, sensors, etc. MnZn ferrites, even with high permeability values, are limited to angular frequencies ranged from kHz to MHz.[1,2,3,4,5,6,7,8,9,10]. The magnetic properties of ferrites are mainly determined by their chemical composition and microstructure (e.g., grain size, bulk density, porosity, etc), which in turn, depends on the process variables, such as shaping method and sintering cycles (mainly sintering temperature, dwell time, and atmosphere composition).[2,11]
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