Magnetic spectra analysis of dielectrics

Method of magnetic spectroscopy is used to analyze and to interpret the experimental data obtained by magnetic measurement of the complex permeability spectra of Mg ferrite and NiZn ferritepolymers. Ferritepolymers were prepared from various concentration of NiZn ferrite particles as a soft magnetic fillers dispersed in PVC polymer matrix. Effect of the filler content on the permeability spectra of NiZn ferritepolymers was examined and compared with presented sintered ferrite samples. The variations of permeability and relaxation frequency due to ferrite filler concentration in composite are presented and discussed from point of view the magnetization processes in samples

High-Frequency Absorbing Performances of Carbonyl Iron/MnZn Ferrite/PVC Polymer Composites

We have prepared composite materials with a mixture of carbonyl iron (CI) and manganese-zinc ferrite (MnZn) as filler and polyvinylchloride (PVC) as polymer matrix, and then electromagnetic wave absorption properties of CI/MnZn/PVC composites have been studied in the frequency range from 10 MHz to 6.5 GHz. Increasing carbonyl iron loading (to the detriment of MnZn ferrite) results in the rise of permeability and magnetic resonance loss (especially in GHz frequency range) which leads to the shift of absorption peak towards lower frequency and to the decrease of matching thickness. On the contrary, increasing MnZn ferrite loading (to the detriment of carbonyl iron) results in higher absorption bandwidth. The obtained results indicate that the prepared flexible composites may be useful as thin and/or wideband microwave absorbers

High-frequency EMI noise suppression by polymer-based composite magnetic materials

The complex permeability and EM-wave absorption properties of hybrid polymer-based composite magnetic materials (with MnZn and LiZn ferrite fillers and PVC matrix) prepared with constant total filler content (65 vol%) and particle size (0-250 mm) have been investigated in the 1-1000 MHz frequency range. Within this filler concentration the permeability of composites changed continuously with the change of ferrite filler content ratio between two types of ferrite fillers. The observed relaxation type of permeability dispersion was due to the domain wall and natural ferromagnetic resonance phenomena and was also attributed to the high damping of spin motion. Measured values of permeability were used to determine the EM-wave absorption properties (return loss RL, matching frequency fm, matching thickness dm and bandwidth Df for RL £ -20 dB). The calculation of these properties was based on a model of single-layered absorber backed by a perfect conductor using transmission-line and EM-field theory. The composite with the volume fraction ratio of hybrid MnZn:LiZn ferrite filler set to 0.5:0.5 has shown a return loss of -57 dB (> 99 % power absorption) at fm = 714 MHz with the -20 dB bandwidth of Df = 232 MHz for an absorber thickness of 7.79 mm. The prepared composites can fruitfully be utilized for suppression of conducted and/or radiated EMI noise especially in wireless and portable electronic equipments

The influence of particle size and substituent contents on the magnetic properties of Be or Cu substituted NiZn ferrites

Polycrystalline NiZn ferrites with the chemical formula (Ni0.3Zn0.7)1−xMexFe2O4 where Me being Be or Cu and x=0.05, 0.1 and 0.25 have been prepared by a ceramic method. Certain magnetic properties such as the coercivity Hc, initial permeability m i, real part of the complex permeability m’ and saturation magnetization Ms of the ferrites have been measured and discussed from the point of view of the substituting element type and contents as well as the average particle size

Microstructural and magnetic characteristics of divalent Zn, Cu and Co-doped Ni ferrites

Divalent zinc, copper and cobalt doped nickel ferrites with the chemical formula Ni_{1-x-y-z}Zn_{x}Cu_{y}Co_{z}Fe₂O₄ where x values ranging from 0.4 to 0.6, y=0.1, z=0.01 and 0.02 have been synthesized by conventional ceramic method. The effect of Zn²⁺, Cu²⁺ and Co²⁺ ions substitution on the selected microstructural and magnetic characteristics have been investigated to examine the utility of prepared ferrite materials for high-frequency applications. X-ray diffraction measurements confirmed the single-phase spinel cubic structure in all the samples and modifications in lattice parameter according to the ionic radii size of doped ions. The net magnetic moment, given by the differences between the magnetic moments of A and B sublattice, increased with raising substitution of Ni²⁺ ions. The measured frequency dispersion of complex permeability was discussed in terms of the changes in chemical composition, microstructure and the associated processes of resonance and/or relaxation due to domain wall movements and damping of spin rotations contributing to the fall of permeability and rise of magnetic losses

Characteristics of magnetic properties of substituted hexagonal ferrites

The samples of barium hexaferrite BaFe12-2x(Me1Me2)xO19 with x from 0.0 to 0.6 were prepared by various methods. The cationic preference of mainly divalent Me1 = Zn, Co, Ni, Sn ions and tetravalent Me2 = Ti, Zr, Ir, Sn, Ru ions and their combinations in substituted Ba ferrites was investigated. The substitutions were performed to reduce the grain size and high magnetic uniaxial anisotropy field of the M-type Ba ferrite without affecting the magnetic polarisation. The goal is to reach the properties of ferrite proper for high-density magnetic recording and microwave absorption devices. Magnetic properties were determined as a function of the substitution level x. The specific saturation magnetic polarisation Js–m and remanence Js–r increased with small x due to the substitution of non-magnetic and less magnetic ions in 4f1 and 4f2 sites. The steep decrease of coercivity Hc with increasing x may be caused by the Co2+ preference of 4f2 site and Ti4+or Zr4+ ions preference of 2b and slightly in 4f1 sites. The temperature coefficient of the coercivity TKHc was very low (0.01kA.m–1.oC–1) for the Co-Zr substitutions and positive for the rest of samples

Kompozyty oparte na kauczuku EPDM napełnione ferrytem strontu

Strontium ferrite was compounded with ethylene-propylene-diene monomer rubber (EPDM) to prepare rubber magnetic composites. Traditional sulfur as well as peroxide curing system were applied for cross-linking of the rubber matrices. The main objective of the work was to investigate the influence of magnetic filler content and type of curing system on the cross-linking, magnetic and physical-mechanical properties of the prepared composites. The results of the study revealed that EPDM based magnetic composites can be efficiently prepared by applying of both, sulfur and peroxide curing systems. Slightly higher values of tensile strength were found to have composites cured with peroxide curing system, what can be attributed to the suitable combination of dicumyl peroxide and co-agent (i.e. ethylene glycol dimethacrylate). The application of strontium ferrite into both type composites leads to a significant improvement of the remanent magnetic induction.Do kauczuku etylenowo-propylenowo-dienowego (EPDM) wprowadzono ferryt strontu w celu uzyskania magnetycznych kompozytów gumowych. Do wulkanizacji mieszanek kauczukowych użyto zarówno tradycyjnych siarkowych, jak i nadtlenkowych zespołów sieciujących. Głównym celem pracy było zbadanie wpływu zawartości magnetycznego napełniacza oraz rodzaju zespołu wulkanizującego na właściwości magnetyczne i fizyko-mechaniczne otrzymanych materiałów kompozytowych. Wyniki uzyskanych badań potwierdziły możliwość efektywnego otrzymywania kompozytów gumowych zarówno poprzez wulkanizację siarkową, jak i nadtlenkową. Nieznacznie większą wytrzymałość na rozciąganie kompozytów usieciowanych za pomocą nadtlenkowego zespołu wulkanizującego można przypisać odpowiedniej kombinacji nadtlenku dikumylu i koagenta (tzn. dimetakrylanu glikolu etylenowego). Zastosowanie ferrytu strontu w obu rodzajach kompozytów przyczyniło się do znacznego zwiększenia szczątkowej indukcji magnetycznej

Effect of Filler Mixture Ratio on Permeability of Multicomponent Soft Magnetic Composites

Composites with hybrid LiZnTi ferrite/FeSiAl alloy filler and PVC polymer matrix were synthesized by thermal pressing process. The influence of the mixture ratio of hybrid filler on the frequency dispersion of complex permeability of the composites has been studied. The dispersion of permeability varied from resonance type to relaxation one with the configuration change from LiZnTi/PVC composite to FeSiAl/PVC one and was mainly due to the magnetic resonance phenomena such as domain wall and spin precession resonance and due to the eddy current effect

Complex Permeability of LiZn/MnZn/PVC Composite Materials

The effect of particle content, size, and the fraction ratio of the double LiZn/MnZn ferrite filler in hybrid LiZn/MnZn/PVC composites on the frequency dispersion of complex permeability has been studied in the 1 MHz-3 GHz frequency range. The obtained relaxation type of permeability dispersion is due to the domain wall resonance, the natural ferromagnetic resonance, and the relaxation of magnetization rotation. The permeability and resonance/relaxation frequency of composites seem to be strongly affected by the change of particle content and fraction ratio of the double ferrite filler rather than by particle size