Rastislav Dosoudil

Frequency dispersion of permeability in ferrite polymer composites

The permeability spectra of sintered MnZn ferrite and magnetopolymers prepared by mixing the ferrite particles with polymer have been studied. The experimental data have been compared with predictions of magnetic circuit model described for dynamic conditions. The applied model analyses the effect of the demagnetising field due to shape and size of ferrite particles.

Composite material with substituted Li ferrite for high-frequency applications

Abstract Magnetic composites using polymer polyvinylchloride (PVC) matrix and Li ferrite of chemical formula Li 0.525 Fe 1.825 Ti 0.35 Zn 0.30 O 4 (LTZF) with treated additions of MnO 2 and Bi 2 O 3 as a magnetic filler, were prepared. The substituted Li ferrite was processed by a conventional solid state reaction and the magnetic parameters, measured on the compact sintered and composite specimens, are presented. The effect of filler quantity on magnetocomposite complex permittivity and microwave absorption has been studied in X-band frequency range.

Influence of Co–Ti substitution on coercivity in Ba ferrites

Abstract Polycrystalline BaCo x Ti x Fe 12−2 x O 19 samples with 0⩽ x ⩽1.2 ions per formula units were prepared by modified citrate precursor method with the initial ratio of Ba:Fe equal to 1:10.8. The cationic site preferences of Co 2+ and Ti 4+ in Co–Ti substituted Ba ferrite were investigated by magnetic measurements and Mossbauer spectroscopy. The coercivity H c , specific magnetic polarisation J s-m ( J s-r ) and Curie temperature T c is decreasing with increasing Co–Ti substitution. The variation of these parameters can be explained by the replacement of the Fe 3+ ions in the 2b and 4f 2 sites, and by splitting the 12k site on the two magnetically non-equivalent sublattices (12k and 12k′), which reduces the effective uniaxial anisotropy of Ba ferrite.

Magnetic permeability study of composite magnetopolymers

The aim of the work is present results of granulometry influence study on the effective permeability of composites with MnZn ferrite filler in the polymer matrix. The frequency dependencies of complex permeability components were measured and discussed with proposal model based on hysteresis and relaxation process.

Microstructure and Performance of Natural Rubber Based Magnetic Composites

Rubber magnetic composites were prepared by incorporation of strontium ferrites in natural rubber-based elastomer matrix. The work was aimed at the evaluation of magnetic filler influence on physical-mechanical, magnetic and thermal properties of prepared composites. The study was also dedicated to the investigation of microstructure and evaluation of interactions between strontium ferrites and natural rubber. The observed parameters are dependent on the type of ferrite and on the content of applied ferrite, too. Surface modification of ferrite leads to the improvement of interfacial conditions and adhesion between the rubber matrix and the magnetic filler.

Magnetic and Structural Properties of Nickel Zinc Ferrites Doped With Yttrium

The aim of this paper is to investigate the effect of Y³⁺ ions substitution for Fe³⁺ ions in Ni_0.42Zn_0.58Y_xFe_2-xO₄(x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) compounds, synthesized by means of ceramic technique, on the magnetic properties and magneto-chemical composition and structure. It was achieved by the X-ray spectroscopy, analysis of the behavior of susceptibility with changing temperature, magnetic hysteresis loop measurement, and complex permeability spectra.

Influence of the Synthesis Method of Filler on Permeability and Microwave Absorption Properties of Ferrite/Polymer Composites

Li0.575Zn0.4Ti0.55Fe1.475O4 ferrite with the addition of 0.005 Bi2O3 and 0.05 MnO2 was synthesized by the ceramic process and the glycine-nitrate process (GNP), and then used as filler in PVC polymer-based composites with variable filler volume loadings (45, 55, and 65 vol%). X-ray diffraction, scanning electron microscopy, and impedance measurement were used to analyze the structural, magnetic, and microwave absorption properties of prepared materials. The single-phase spinel structure of the ferrites was confirmed by XRD analysis. The ferrite synthesized by GNP achieved a fine-grained and more uniform microstructure. Frequency dispersion of the permeability of the composites was observed in the microwave frequency region, which was due to domain wall and natural ferromagnetic resonance. The improved return loss (RL) and the bandwidth for RL ≤ -20 dB of the composites with filler prepared by GNP are considered to be related to the increased permeability in the gigahertz band (over 1 GHz) and to a broader magnetic loss.

Magnetic Properties Analysis of Rare-Earth Substituted Nickel Zinc Ferrites

The raw compounds with the chemical composition Ni_0.42Zn_0.58Me_xFe_2-xO₄ where Me = Eu, Gd, La (x = 0, 0.01, 0.02, 0.04, 0.06) were synthesized by means of the ceramic technique. The magnetic properties and magneto-chemical composition and structure of various doped nickel zinc ferrites were estimated by X-ray spectroscopy, EDAX analysis, and study of the behavior of susceptibility with changing temperature, complex permeability spectra, and magnetic hysteresis loop measurement.

Influence of peroxide curing systems on the performance of natural rubber-based magnetic composites

Rubber magnetic composites were prepared by incorporation of strontium ferrite into natural rubber-based continuous matrix. The prepared rubber compounds have model character and besides the rubber and the filler, they contained only ingredients of peroxide curing system, dicumyl peroxide as curing agent, and ethylene glycol dimethacrylate as co-agent. The work was focused on the evaluation of curing system composition and magnetic filler content on curing process, cross-link density, physical–mechanical and magnetic properties of tested materials. The achieved results revealed that the evaluated properties are dependent on the composition of curing system and on the content of ferrite too. Ferrite incorporated in the rubber matrix imparts magnetic properties to the composites considerably. In addition, the improvement of physical–mechanical properties with doping content of ferrite was observed.

Changes of Ni-Zn Properties by Substitution of Zn With Cu and Co Ions

The effect of partial substitutions of Zn²⁺ ions with Cu²⁺ and Co²⁺ ions in Ni_0.33Zn_0.67Fe₂O₄ ferrite were investigated on magnetic properties. Fine particles of Ni_0.33Zn_0.67-xMe_x, ferrites with Me = Cu²⁺/Co²⁺ were prepared by the self-propagated combustion method. Variation of temperature dependences of the magnetic susceptibility χ(T) with composition is discussed and possible magnetic mechanism is investigated. Grain size is one of the factors determining the magnetic properties of ferrite materials. The chemical and structural changes of ferrite during substitution treatment are analyzed also using Mossbauer spectrum and SEM. Initial permeability varies with ion content x in ferrite materials, which is attributed to the variation of grain size.