Magnetic complex permeability (imaginary part) dependence on the microstructure of a Cu-doped Ni–Zn-polycrystalline sintered ferrite

Abstract

In this study, the effective complex magnetic permeability-imaginary part (μeff'') of a Cu doped-NiZn polycrystalline ferrite used as EMI suppressor has been quantitatively related to microstructural parameters. It has been observed that μeff'' strongly depends on average grain size (G) of the compact, but also on its relative density ϕ: the higher grain size and density the higher μeff''. A mathematical relationship between μeff'' and average grain size and densification has been proposed and tested, accurately reproducing the experimental results. The use of densification concept allows to compare the wide range of microstructures tested and includes a lower value of relative density (estimated around 0,56) below which μeff'' is virtually zero. The grain boundary thickness (δ) has been estimated around 2 nm which is in agreement with experimental results reported in this work and with those found in literature.