Mariana Usakova

Analysis of Magnetic Properties of Substituted Li Ferrites

Substituted Li ferrites with chemical composition Li_0.5+0.5 <i>t</i> -0.5<i>x</i>Fe_2.5-1.5 <i>t</i>-0.5<i>x</i>Ti<i>t</i>Zn<i>x</i>O₄, where <i>x</i> = 0.20 and <i>t</i> = 0.35, 0.45, 0.55 with additions of 0.005 Bi₂O₃ and 0.05 MnO₂ were synthesized by ceramic method and from solutions of metallic salts and citric acid. The intrinsic and extrinsic magnetic properties were measured and are discussed from the point of view of the substituting element content as well as the grain size. The magnetic polarization, Curie temperature, saturation induction, susceptibility, and coercivity were measured and the Mossbauer spectra of certain samples have been analyzed. According to the requirements in specific applications, the properties of LiZnTi ferrite can be improved by means of proper substitution of selected ions and processing technology.

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.

Analysis of Selected Be-Substituted NiZn Ferrites

Polycrystalline NiZn ferrites with the chemical formula (Ni_0.3Zn_0.7)_1- <i>x</i>Be<i>x</i>Fe₂O ₄with Be substituent ion <i>x</i>=0, 0.05, 0.1, and 0.25 have been prepared by the ceramic method. The intrinsic and certain extrinsic magnetic properties such as the coercivity <i>H</i> _c, initial permeability ¿<i>i</i>and hysteresis loops of the ferrites have been measured and discussed from the point of view of the substituting element contents as well as the grain size. The MO¿ssbauer spectra of certain samples have been analysed as well. According to the requirement of specific applications the properties of NiZn, ferrite have to be improved by means of proper substitution of selected ions and processing technology.

Effect of lanthanum substitution on structural and magnetic properties of nickel zinc ferrites

The purpose of the presented research is to investigate the effect of La3+ ions substitution for Fe3+ ions in Ni0.42Zn0.58LaxFe2-xO4 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) ferrite compositions prepared by the innovated glycine-nitrate process based on auto-combustion method. Structural and magnetic properties of examined samples were estimated by the analysis of X-ray spectra, EDAX spectrum, SEM micrographs, thermomagnetic characteristics, magnetic hysteresis loops and complex permeability spectra.

Influence of iron substitution by selected rare-earth ions on the properties of NiZn ferrite fillers and PVC magneto-polymer composites

Nickel-zinc ferrites are very important soft magnetic materials from the point of view of diverse technical applications (such as, e.g., various electronic devices and components) for their high magnetic permeability and permittivity, low core loss, high resistivity, high Curie temperature as well as mechanical strength and chemical stability. Due to their good absorbing properties, they can be used as microwave absorbing and shielding materials with the aim of decreasing the environmental pollution caused by non-ionizing microwave radiation. The ferrite material incorporated into the polymer matrix creates qualitatively new magneto-polymer composite material taking benefits from both components. The properties typical for polymers (elasticity, mouldability, etc.) are combined with good high-frequency magnetic parameters, thus allowing to utilize these materials, e.g., in high-frequency applications where especially flexibility of composite materials plays a key role. Small amounts of selected rare-earth ...

Analysis of Microstructural Changes in Soft Magnetic Materials Based on Direct Evaluation of Magnetization Process Dynamics

A correlation between thermal aging and the dynamics of magnetization processes (especially domain wall motions) in standard steel sheet materials were studied. The response of magnetic quantities, e.g., the flux density and/or induced voltage, to artificial aging induced by annealing of the samples at 753 K for aging time ta ranging from 0 to 60 h was investigated. Ring-shaped samples were magnetized with defined exciting field having special waveform shape allowing direct observation of transients associated with sudden change of waveform attributes (e.g., slope). The parameters of observed first-order exponential-like transient curves were demonstrated to be influenced by heat treatment of the samples. Obtained results allow the application of suggested procedure as a promising new method for nondestructive inspection of various ferromagnetic construction materials.

Magnetic properties of Ni ferrites substituted by divalent Zn, Cu and Co ions

Substituted Ni ferrite samples with chemical composition Ni_1-x-y-zZn_xCu_yCo_zFe₂O₄, where x = 0.4, 0.5 and 0.6, y = 0.1, z = 0.01 and 0.02 were prepared by classical ceramic technology at the temperature of 1200°C. The influence of divalent Zn, Cu and Co ions substitution on the magnetic properties of spinel Ni ferrites was studied. The magnetic properties, such as the Curie temperature, coercive field, remanent magnetic flux density, hysteresis loop area as well as the amplitude and initial permeability were investigated by means of thermo-magnetic analysis and magnetisation curves measurements at low frequencies.