M. Šoka

HOPKINSON EFFECT STUDY IN SPINEL AND HEXAGONAL FERRITES

Hopkinson Effect Study in Spinel and Hexagonal Ferrites The magnetic susceptibility shows a Hopkinson peak just below the Curie temperature TC when heating the selected hexagonal and spinel ferrite samples. It is proposed that this peak can be associated with a transition from stable magnetic state to super-paramagnetic relaxation above the blocking temperature up to the TC. The Hopkinson effect results are compared with SEM micrographs of both studied hexagonal and spinel ferrites.

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.

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.

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.

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.

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 ...