Abstract
We report results on the structural and microwave properties and magnetic phase transitions in polycrystalline Sr3Co2Fe24O41 hexaferrite synthesized by sol-gel auto-combustion and acting as a filler in a composite microwave absorbing material. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves revealed a change in the magnetization behavior at 293 K. The reflection losses in the 1–20 GHz range of the Sr3Co2Fe24O41 powder dispersed homogeneously in a polymer matrix of silicon rubber were investigated in both the absence and presence of a magnetic field. In the latter case, a dramatic rise in the attenuation was observed. The microwave reflection losses reached the maximum value of 32.63 dB at 17.29 GHz in the Ku-band. The sensitivity of the microwave properties of the composite material to the external magnetic field was manifested by the appearance of new reflection losses maxima. At a fixed thickness tm of the composite, the attenuation peak frequency can be adjusted to a certain value either by changing the filling density or by applying an external magnetic field.
Highlights
In recent years, intensive efforts have been focused on the development of optimized electronic equipment, such as antennas, modems, mobile phones, magnetic recorders, etc., operating in the microwave, mainly gigahertz, range
We report on the structural, magnetic and microwave properties of a Sr3 Co2 Fe24 O41 material synthesized by sol-gel auto-combustion with sugar as a fuel, and on its use as a filler in a polymer matrix to form a composite performing as a microwave antireflection material
Unlike the preparation of M-type hexaferrites ((Ba,Sr)Fe12 O19 ) by “wet chemistry”, the complexity of the Z-type hexaferrite structure imposes the need of a progressive transformation through intermediate ferrites before achieving the final structure
Summary
Intensive efforts have been focused on the development of optimized electronic equipment, such as antennas, modems, mobile phones, magnetic recorders, etc., operating in the microwave, mainly gigahertz, range. Operation at such frequencies may encounter serious problems arising when the transmission/emission of electromagnetic (EM) signals from an unwanted source is jamming through electromagnetic interference (EMI) the electronic devices functioning in a similar frequency range [1]. Among the most commonly used magnetic materials are the ferrites, which are structurally classified as spinels, garnets and hexaferrites.
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