Variation Of Initial Permeability Research Articles

Structure, electromagnetic and dielectric properties of Ti-substituted lithium--zinc ferrite

Li0.35+0.5xZn0.3TixFe2..35–1.5xO4 (x = 0–0.4) ferrites waere prepared via a solid-state method. XRD refinement results show that diamagnetic Ti4+ ions enter octahedral lattice and replace Fe3+ at B site, resulting in the redistribution of B sublattice magnetic moment and ultimately reducing saturation magnetization. This mechanism is analyzed from the perspective of ion occupying distribution and substitution law. Globus relation is used to qualitatively analyze the law of initial permeability change with temperature and titanium content, and the main influencing factors are revealed. The variation of initial permeability and permeability loss with frequency and its causes have been explored, which are attributed to domain wall displacement, domain rotation and various resonance effects, especially domain wall resonance. The dominant characteristics and main influencing parameters of the three types of power losses in different frequency bands were studied quantitatively, and the transition law of the main mechanism of power losses with the change of frequency was explored. The variation of dielectric properties with frequency, titanium content and temperature was studied and analyzed utilizing polarization mechanism and Koops model.

Structural and magnetic properties of V2O5-Na2SiO3 added Li0.5Fe2.5O4 spinel ferrite ceramics prepared by high energy ball milling

Spinel lithium ferrite ceramics inherently possess useful properties like high resistivity, saturation magnetization and Curie temperature, rectangular hysteresis loop and low dielectric and magnetic losses. They find widespread applications in high frequency electronic devices. Attempting an enhancement in the properties of interest, lithium ferrites were prepared by adding V2O5 and Na2SiO3 additives. Samples having Li0.5 Fe2.5O4 + (0.1) V2O5 + (x) Na2SiO3 as representative formula where x = 0.0, 0.05, 0.10, 0.15, 0.20, 0.25 were prepared by the ceramic technique using high energy ball milling. The prepared samples were calcined at 650 °C for 1h and sintered at 950 °C for 1h. XRD was done on the sintered samples and it is found that the samples possessed single phase with spinel structure. From the XRD data various structural parameters were evaluated. The microstructure of these samples was studied from the SEM micrograph. The room temperature frequency variation of initial permeability and permeability loss were measured in the range 5MHz to 40MHz using an impedance Analyzer. The results of these measurements are discussed in the paper.

Co2+ substituted Mg\u2013Cu\u2013Zn ferrite: Evaluation of structural, magnetic, and electromagnetic properties

We report the synthesis of Co2+ substituted Mg–Cu–Zn ferrite via citrate gel combustion process and thereby its structural, transport, and magnetic properties for the use in electromagnetic energy absorption application. The polycrystalline ferrite system is investigated by interplay of stoichiometric composition with Mg0.25–xCoxCu0.25Zn0.5Fe2O4 (0 ⩽ x ⩽ 0.25). Structural investigations using X-ray diffraction (XRD) and selected area electron diffraction (SAED) reveal the formation of spinel structure with linear growth of lattice constant due to Co2+ substitution. The microstructural analysis (TEM and SEM) depicts the dense microstructure with the average grain size of 0.42–1.25 μm. The elemental analysis (EDS) confirms the elemental composition of the as-prepared ferrite with respect to the initial concentrations of the synthetic composition used. The observed variations in initial permeability (μi) and magnetic moment (nB) are explained based on deviation in saturation magnetization (Ms), anisotropy constant (K1), density values, and exchange interaction. The temperature dependence of DC resistivity confirms the semiconducting behavior of the as-prepared ferrite material, with an increase in the DC resistivity by an incorporation of cobalt. Furthermore, the effects of adding Co2+ on the Curie temperature, frequency dependent dielectric properties of the ferrite material are also discussed.

Investigation of Room Temperature Mössbauer Spectroscopy and Initial Permeability Properties of Al3+ Substituted Cobalt Ferrites

In the present work, Al[Formula: see text] substituted cobalt ferrites (CoFe[Formula: see text]AlxO4, [Formula: see text], 0.4, 0.6, 0.8) have been synthesized via standard solid-state reaction technique. The incorporation of Al[Formula: see text] ions in cobalt ferrite has been shown to play an important role in modifying the magnetic properties. The room temperature (300[Formula: see text]K) [Formula: see text]Fe Mössbauer spectra reveals that the studied samples show two characteristic ferromagnetic zeeman sextets at A and B-sites at lower Al[Formula: see text] ion concentration (i.e., up to [Formula: see text]). However, a paramagnetic relaxation has been noted for higher Al[Formula: see text] substitution (for [Formula: see text] and 0.8) samples. The dependence of the Mössbauer parameters such as isomer shift, quadrupole splitting, line width and magnetic hyperfine field on Al[Formula: see text] ion concentration has also been noted. The variations in initial permeability over a wide frequency range (125[Formula: see text]kHz to 30[Formula: see text]MHz) at 300[Formula: see text]K have been recorded. The fairly constant values of initial permeability and the low values of the relative loss factor of the order of 10[Formula: see text] to 10[Formula: see text] over the wide frequency range are the important findings of the present work. The observed low values of relative loss factor at high frequencies suggest that the studied ferrites are promising materials to be used in microwave applications.

Multiferroic properties of microwave sintered PbFe12−xO19−δ

The effect of iron deficiency on the structural, electrical, ferroelectric and magnetic properties of nano PbFe12-xO19-δ (where x=0.0, 0.25, 0.50, 0.75, 1.0) hexaferrites prepared by sol-gel auto combustion and processed by microwaves are investigated. X-ray analysis confirms single phase magneto-plumbite phase formation. The surface morphology is studied from Field Emission Scanning Electron Microscope. Further, optical properties are investigated using Fourier Transform Infrared spectra and UV–visible spectra. AC electrical conductivity is estimated as a function of temperature and frequency in the range of room temperature (RT) to 500°C and 100Hz to 5MHz. AC electrical conduction analysis shows that conduction is mainly due to small polaron hopping mechanism. The variation of polarization with applied electric field exhibits hysteresis loop confirming the ferroelectric nature. The initial permeability studies with varying temperature reveals that the Curie transition temperature for the present series is around 400°C. Variation of initial permeability with frequency ranging from 100 to 5MHz shows a constant value (except for x=0.0) opening avenues for high frequency applications.

Spin canting observation and cation distribution in CoFe2−xInxO4 (0.0 ⩽ x ⩽ 1.0) ferrites through low temperature–high field Mössbauer spectral study

In the present work, In3+ substituted cobalt ferrites (CoFe2−xInxO4, x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) have been synthesized via solid-state reaction technique. The Rietveld fitted X-ray diffraction patterns confirm the formation of single phase cubic spinel structure with space group Fd3¯m for all the samples, with additional slight traces of secondary phase for x=0.6, 0.8 and 1.0 samples. The low temperature (5K)–high field Mössbauer (5T) spectra are analyzed in detail for probing the magnetic properties of Fe based In3+ substituted cobalt ferrites. The canted spin structures associated with Fe3+ ions both at A- and B-sites in the presence of external magnetic field of 5T have been noticed in all the samples. A fair agreement is obtained between the experimental integrated intensity ratios of 57Fe Mössbauer spectra at A- and B-sites and those calculated on the basis of cation distribution. The effect of In3+ substitution on various Mössbauer parameters viz hyperfine field distribution, isomer shift, quadrupole splitting and the line width has also been noticed. The magnetization measurements performed at low temperature also reveal the canted spin structures in all the samples. The variations in initial permeability over a wide range of frequency (125kHz–30MHz) at 300K have also been recorded. The initial permeability study reveals the occurrence of resonance phenomenon at very high frequencies which widens the area of utility of considered ferrites in the larger operational frequency range for various industrial applications.

Magnetic studies on LiFe5−xMnxO8 (0 ⩽ x ⩽ 0.9) ferrites

A systematic investigation of Mn doped lithium ferrites with composition formula, LiFe5−xMnxO8 (x=0.0–0.9) have been undertaken mainly to explore the magnetic properties with possible underlying mechanism. The materials were prepared by sol–gel method and structural characterization was carried out by X-ray diffraction and scanning electron microscopy measurements. The room-temperature magnetic properties such as saturation magnetization, initial permeability, quality factor, etc. of these ferrites were analyzed as a function of Mn ion concentration. The value of saturation magnetization is found to decrease with increasing Mn concentration and the reason for underlying mechanism is discussed. The variations in initial permeability, quality factor with frequency, including the observed resonance phenomena around 3MHz frequencies in these materials have been qualitatively explained. The results revealed that the Mn concentration was strongly influence the Curie temperature of Mn doped lithium ferrites.

Microstructure and magnetic studies of Mg–Ni–Zn–Cu ferrites

Soft Mg–Ni–Zn–Cu spinel ferrites having general chemical formula Ni x Mg 0.5− x Cu 0.1Zn 0.4Fe 2O 4 (where x = 0.1, 0.2, 0.3, 0.4 and 0.5) were prepared by standard double sintering ceramic method. The samples were characterized by X-ray diffraction at room temperature. The X-ray diffraction (XRD) study revealed that lattice parameter decreases with increase in Ni content, resulting in a reduction in lattice strain. The electrical and magnetic properties of the synthesized ferrites have been investigated as a function of temperature. The variation of initial permeability and AC susceptibility with temperature exhibits normal ferrimagnetic behavior. The variation of initial permeability with frequency is studied. The Curie temperature ( T C) in the present work was determined from initial permeability and AC susceptibility. The Curie temperature increases with Ni content.

Studies on initial permeability and loss factor in Ni–Zn ferrites synthesized by oxalate precursors

Abstract Ni X Zn 1− X Fe 2 O 4 ferrites with ( X = 0.28–0.40 in step of 0.2) have been synthesized by oxalate precursor method and investigated for their, initial permeability and loss factor measurements. Initial permeability has been observed to increase with the increase in Ni 2+ up to X = 0.32, beyond which it decreases. The variation of initial permeability has been explained by considering the factors such as grain size, saturation magnetization and anisotropy constant. Thermal variation of initial permeability reveals a peak height in μ i – T curves which tends to increase with increase in Ni 2+ content. μ i – T curves also exhibit thermal hysteresis, which reveals the inverse relationship between the difference in heating and cooling curves at which hysteresis falls between Hopkinson peak and T c with value of initial permeability. Loss factor values are small which is attributed to high density of the samples and processing techniques.

Influence of Cd 2+ and Cr 3+ substitutions on the magnetization and permeability of magnesium ferrites

Magnetization and permeability of polycrystalline ferrites with general formula Cd x Mg 1− x Fe 2− y Cr y O 4 ( x=0, 0.2, 0.4, 0.6, 0.8, 1.0; y=0, 0.05 and 0.10) were studied. Study of saturation magnetization reveals that the Neel's two-sublattice model exists upto x=0.4, for y=0, 0.05 and 0.1 and a three-sublattice model ( YK-model) is predominant for x>0.4 and y=0, 0.05 and 0.10. The saturation magnetization and magnetic moment were found to decrease with the increase in Cr 3+ contents, which is attributed to the dilution of B–B site interaction. Variation of initial permeability with temperature revealed the long-range ferromagnetic ordering in the compounds with x=0.4. The sample with x⩽0.4 and y=0, 0.05 and 0.10 showed peaking behavior near Curie temperature, which is attributed to the decrease of anisotropy constant K 1 to zero. Low-frequency dispersion of initial permeability suggests domain wall displacement. Addition of Cd 2+ resulted in a sharp decrease in Curie temperature. With the addition of Cr 3+, initial permeability was found to decrease.

Kinetics and magnetic properties of sol–gel derived NiZn ferrite–SiO 2 composites

NiZn ferrite–SiO 2 composites are synthesized by a sol–gel method. The chemical and structural changes of gels during heat treatment are analyzed using DTA, infrared spectra (IR) spectra and XRD. Several kinetic models in predicting the formation of ferrite are assessed. The result indicates that the rate of ferrite formation in sol–gel derived composites is best represented by Blum and Li's equation, d x/d t=( k−x)/ t. Variation of initial permeability with composition is discussed and possible magnetic mechanisms are investigated. Grain size and the continuity of magnetic circuit are the main factors to determine magnetic properties of ferrite composite materials.

Microstructure and permeability studies of mixed Li-Cd ferrites

Some microstructure-related properties of Li 0.5− x/2 Cd x Fe 2.5− x/2 O 4 ferrites have been reported. SEM micrographs show an interesting grain growth mechanism. Grain size increases up to x=0.3 and then decreases very slowly beyond it. Saturation magnetisation also follows the same trend. But initial permeability shows continuous increase up to x=0.6 and is explained on the basis of non-magnetic grain-boundary model. The variation of initial permeability and AC susceptibility with temperature shows normal ferrimagnetic behaviour. The Curie temperature decreases continuously with x, which is attributed to the decrease in the strength of the A–B interaction.

Magnetic and microstructural properties of Sn/Nb substituted Mn–Zn ferrites

Saturation magnetisation, Curie temperature and initial permeability of Sn/Nb substituted Mn–Zn ferrites have been studied at room temperature. The influence of high valency cations on the microstructure has been studied. Grains of monodomain form are obtained and the variation of initial permeability with grain size is discussed in the light of recent studies on Mn–Zn ferrites, where initial permeability variation with grain size was explained on the basis of the Pankert model. The variation of saturation magnetisation and Curie temperature with dopant cation concentration is explained.

The variation of initial permeability of amorphous ribbons with frequency and annealing conditions

The published values of the initial permeability of amorphous ribbons have been obtained at a flux density of 50 G (5 mT), but it is shown in this study that these values are not the true initial permeability due to the curvature of the B/H characteristic below 20 G (2 mT). The true initial permeability of Metglas 2605SC type material (Fe 81 B 13.5 Si 3.5 C 2 ) and Vitrovac E6010 type material (Co 58 Fe 5 Ni 10 Si 11 B 16 amorphous ribbons has been measured, over the frequency range 20 Hz to 20 KHz for various annealing conditions, i.e. temperature from 325°C to 425°C, field and non-field conditions and atmospheres of air, nitrogen and hydrogen. For Metglas 2605SC type material at flux densities below 5 mT (50 G) lower magnetizing fields are necessary for materials annealed at the higher temperatures. Above 5 mT the optimum annealing temperatures depends upon the operating frequency of the material. The initial permeability of Metglas 2605SC type material is more sensitive to annealing temperature than to field conditions. For Vitrovac E6010 type material field annealing dominates the effect of annealing temperature. The highest values of true initial permeability are obtained for field anneals in hydrogen for both materials. These variations in initial permeability with frequency and annealing conditions are explained by considering the domain structure, stress conditions in the ribbon, domain wall anisotropy and the surface effects of the gas atmospheres.

Domain rotation and wall displacement contributions to permeability in YIG

The variation of initial permeability, μi, with temperature is studied in polycrystalline normal sintered (large grain size) and hot pressed (small grain size) YIG. The contributions to μi due to domain wall displacement and domain rotation are estimated based on Zener's relation for the temperature dependence of anisotropy. In polykristallinem, normal gesintertem (große Körner) und heiß gepreßtem (kleine Korngröße) YIG wird die Änderung der Anfangspermeabilität μi mit der Temperatur untersucht. Die Beiträge zu μi durch Domänenwandverschiebung und Domänendrehung wird mit der Zenerschen Beziehung für die Temperaturabhängigkeit der Anisotropie berechnet.

Variation of Initial Permeability with Direction in Single Crystals of Silicon-Iron

Variation of Initial Permeability with Direction in Single Crystals of Silicon-Iron