Ferrite System Research Articles

Effect of Sm3+ substitution on dc electrical resistivity and magnetic properties of Ni–Co ferrites

Sm3+ substituted Ni–Co ferrite materials have been developed with the chemical compositions Ni0.5Co0.5Fe2-xSmxO4 for x = 0.0, 0.02, 0.04, and 0.06 by solid-state method. A spinel with a single-phase cubic structure was found through XRD analysis. Crystallite size and lattice parameter fluctuation with Samarium content, decreasing with Sm3+ doping. When Sm3+ is doped, SEM shows a uniform distribution of grains with increasing agglomeration, and the grain size decreases with samarium concentration. Two peaks of absorption mode FTIR spectra show their spinel nature. The samples' negative temperature coefficient measured by the two probe method indicates their semiconducting nature. The DC electrical resistivity of the Ni–Co ferrite system was found to increase from 5.99 × 103 (Ω-cm) to 9.89 × 109 (Ω-cm) as an increase in Sm concentration. VSM measurement gives the saturation magnetization for the concentration up to x = 0.04 decreased and then increased for x = 0.06. All these properties show our samples' higher applicability in various electronic devices.

Synthesis of Nickel-Zinc Ferrite Nanoparticles by the Sol-Gel Auto-Combustion Method: Study of Crystal Structural, Cation Distribution, and Magnetic Properties

Spinel ferrite nanocomposites of Ni1–xZnxFe2O4 (x = 0.25 and 0.75) were synthesized by sol-gel auto-combustion and annealed between 250°C and 1000°C. A single-phase spinel structure was found through X-ray diffraction (XRD). The crystallite size is in the range of 17.55–66.98 nm, and lattice parameters are in the range of 8.351–8.434 Å. X-ray analysis revealed a slight shift of the peaks towards shorter angles when the zinc concentration increased from 0.25 to 0.75. XRD measurements revealed the metal ion distribution in the spinel ferrite system. For each sample, XRD data were used to compute structural characteristics such as lattice spacing, lattice constant, crystallite size, oxygen position parameter, tetrahedral and octahedral ionic radii, and bond lengths. Energy dispersive spectroscopy (EDS) spectra and field emission-electron scanning microscope (FESEM) were used to evaluate the elemental content and morphology. EDS analysis confirmed the presence of expected elements in the samples and confirmed the high doping rate of more than 180% of Zn ions in Ni ferrite. The evaluated particle sizes were determined to be 79.2 and 118.4 nm for zinc content of 0.25 and 0.75, respectively. The nearly spherical shape of the nanoparticles was shown in the transmission electron microscope (TEM). The magnetic moment, remanent, coercivity, and saturation magnetization were calculated by using vibrating sample magnetometer (VSM) results. The saturation magnetization magnitudes showed the influence of cation distribution.

Flux Method Growth and Structure and Properties Characterization of Rare-Earth Iron Oxides Lu1−xScxFeO3 Single Crystals

Perovskite rare-earth ferrites (REFeO3) have attracted great attention for their high ferroelectric and magnetic transition temperatures, strong magnetoelectric coupling, and electric polarization. We report on the flux method growth of rare-earth iron oxide Lu1−xScxFeO3 single crystals through a K2CO3-B2O3-Bi2O3 mixture as a flux solution, and give a detailed characterization of the microstructure, magnetism, and ferroelectric properties. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) measurements revealed that the obtained single crystals can be designated to three different crystal structures of different chemical compositions, that is, Lu0.96Sc0.04FeO3 (perovskite phase), Lu0.67Sc0.33FeO3 (hexagonal phase), and Lu0.2Sc0.8FeO3 (bixbyite phase), respectively. Magnetic measurements indicate that the perovskite Lu0.96Sc0.04FeO3 is an anisotropic hard ferromagnetic material with a high Curie transition temperature, the bixbyite Lu0.2Sc0.8FeO3 is a low temperature soft ferromagnetic material, and the hexagonal Lu0.67Sc0.33FeO3 exhibits multiferroic properties. Lu0.67Sc0.33FeO3 possesses a weak ferromagnetic transition at about 162 K. We further investigate the ferroelectric domain structures in hexagonal sample by scanning electron microscope and the characteristic atomic structures in ferroelectric domain walls by atomically resolved scanning transmission electron microscope. Our successful growth of perovskite Lu1−xScxFeO3 single crystals with distinct crystal structures and stochiometric Lu-Sc substitutions is anticipated to provide a useful ferrites system for furthering exploitation of their multiferroic properties and functionalities.

Preparation and properties of Sr(CrMnFeCoNi)3O4 and Sr(MgAlTiCrFe)12O19 high entropy strontium ferrite systems and valance state analysis

Two high-entropy ferrite ceramic systems, Sr(CrMnFeCoNi)12O19 and Sr(MgAlTiCrFe)12O19, were designed according to AB12O19 composition and synthesised using elevated-temperature solid phase reaction. The B-site was loaded with five atoms in equal proportions. We focused on preparing high-entropy hexagonal magnetoplumbite strontium ferrites. However, spinel structure significantly formed in the Sr(CrMnFeCoNi)12O19 system. The extruded strontium outside the lattice pulled out a part of chromium, causing phase separation and element segregation. The strontium extrusion outside the lattice and non-formation of hexagonal ferrite, which was reported for the first time, could be attributed to the electrovalence change in the elements. First-principles calculation of the (CrMnFeCoNi)3O4 spinel system was used to analyse the band structure and density state. After entropy engineering design, it was mutated into a wide direct band gap (2.3 eV at 0 K). Although the non-magnetic elements reduced the magnetic performance, they significantly improved the mechanical performance with a flexural strength of 208.7 ± 0.9 MPa. These results may contribute to the element selection and preparation of high-entropy strontium ferrites.

FTIR and Electrical Properties of Cr Substituted Li0.5Fe2.5−xO4 Synthesized Using Sol-Gel Auto Combustion

The highly desirable properties of lithium ferrite and various metal ion substituted lithium ferrite make it a useful material for many electronic and magnetic applications. This research used a simple sol-gel auto-combustion method for the synthesis of Cr substituted Li0.5Fe2.5O4 ferrite. Here, in the B-site, Fe3+ ions were swapped by non-magnetic Cr3+ ions at different concentrations. All the samples of Cr substituted Li0.5Fe2.5O4 were confirmed through X-ray diffraction patterns to have a single-phase spinel-type structure with cubic symmetry, which was thereafter confirmed by its refinement through Rietveld. An increase in the substitution of Cr3+ instead of Fe3+ ions in the spinel ferrite system results in an increased nanocrystalline size. The average crystallite size decreased from 30 nm to 10 nm with an increase in Cr3+ content. Analogous particle size was evaluated through transmission electron microscopy (TEM) analysis. Fourier transform infrared spectroscopy (FTIR) provides an overview of the structural distortion of the lithium ferrite lattice with the substitution of Cr3+ ions. The Semiconducting (NTCR) nature of the Cr substituted Li0.5Fe2.5O4 nanoparticles was confirmed through the temperature-dependent DC resistivity. The evaluated trend of the dielectric properties (ε′, ε″, and tan δ) strengthens the facts observed in the electrical conduction mechanism.

Annealing temperature dependence of crystalline structure and magnetic properties in nano-powder strontium-substituted cobalt ferrite

Strontium-substituted cobalt ferrite nanoparticles were synthesised via the co-precipitation method. Thermogravimetric analysis (TGA) showed that the relative reduction of the mass was supported by the available strontium cations. X-ray diffraction analyses clarified that single-phase nanoparticles were obtained and indicated that the strontium cations substituted metal cations in the cobalt ferrite nanoparticle system. The crystallite size increased on increasing the annealing temperature. By contrast, the crystalline stress decreased on increasing the annealing temperature. Furthermore, the saturated magnetisation decreased with an increased annealing temperature. Finally, the annealing temperature dependence of the coercive field is shown in this paper and the highest coercive field, HC, of 2.76 kOe is obtained for Sr0.1Co0.9Fe2O4 nanoparticles with an annealing temperature of 1000 °C. Here, the Sr2+ cations facilitate the high value of the anisotropic magnetic realisation for the whole annealing temperature treatment.

Preparation and characterization of Sr-doped LaFeO3

The present work is intended to increase orthorhombic distortion in lanthanum ferrite system by incorporating Sr as a dopant in lanthanum ferrite (La1-xSrxFeO3) [x = 0.02, 0.04, 0.06, 0.08, 0.10]. The systems are synthesized via Sol-gel combustion method. Structure is confirmed by X-ray diffraction (XRD). The Rietveld refined XRD data confirms the orthorhombic crystal structure of LFO and LSFO belongs to space group Pbnm. Impedance modulus and Nyquist plot were studied from Impedance spectroscopy data. To check its potential as a dielectric, frequency dependence dielectric behavior was studied. Frequency-dependent dielectric constant showed dispersive behavior at low frequencies with low loss.

Metamagnetic effect in selected MnMg ferrite

A few studies are available on MnMg ferrites, but there is missing information about these ferrites from the point of view of metamagnetic nature. Therefore, in the present study, we have focused on metamagnetic properties of selected MnMg ferrite. The magnetic properties of ferrites having the formula Mn0·894Mg0·347Fe1·758O3.88 prepared by the ceramic technique have been studied. Magnetic measurement has been carried out for examined compound from low magnetic field up to critical field intensity 580 A/m. The composition indicated metamagnetic nature below critical field intensity. In adequate low applied field the formation and increasing of magnetic induction with temperature is caused by changes from canted triangular model to two sublattices model of ferrimagnetic spinel structure. This suggests the existence of canted spin structure in the MnMg ferrite system. Ferrimagnetic properties have been measured by hysteresis loop tracer technique for wide scale of temperatures. Barkhausen noise analysis demonstrated that the magnetizing is prevalently possessed with mechanism of the domain walls motion.

Magnetic characterization of self-assembled nanostructures in cobalt ferrites using first-order reversal curve (FORC) analysis

Magnetic ceramics are important for numerous technologically relevant applications with a detailed understanding of structure, property, and processing inter-relationships playing a critical role in tailoring magnetic properties. Spinel ferrites are a particularly interesting class of magnetic ceramics of chemical formula AB2O4, with applications including biomedical hyperthermia and high frequency electrical power conversion. In this contribution, we seek to investigate a unique class of Co-ferrites in which spinodal decomposition can produce a ferrite nanocomposite with chemistry and stress state fluctuating within the interior of crystalline grains on the nm-scale, resulting in corresponding fluctuations of intrinsic magnetic properties as well as exchange and magnetostatic interactions. Structural and magnetic characterization of spinel ferrite samples are carried out (1) in the as-milled state prior to thermal processing, (2) after chemical and structural homogenization with a thermal calcination step, and (3) in the spinodal decomposed state following a subsequent annealing treatment within the Co-ferrite miscibility gap. Of note is the formation of a wasp-waisted hysteresis loop which emerges for the spinodal decomposed Co-ferrite sample, indicative of more complex magnetization reversal processes at relatively large applied fields than for homogeneous Co-ferrite samples of similar particle size and identical nominal chemistry. First order reversal curve (FORC) analysis is applied to further characterize the magnetization response, and a conventional interpretation of observed features in the FORC contrast is presented to discuss potential dominant magnetization mechanisms. The work described here represents the first application of FORC to spinodal decomposed magnetic ceramics and provides a strong foundation for future investigations seeking to quantitatively describe the impacts of nm-scale chemical, structural, and magnetic fluctuations on magnetization processes in ferrite spinel nanocomposite systems.

Experimental Compressive Strength and Microstructure Analysis of Magnesium Fluxed Pellets

In this paper, Zhong Guan iron ore is used as raw material. By adjusting the content of lime, raw magnesium powder and bentonite, the effect law of different SiO₂, MgO content and alkalinity on the compressive strength of pellet ore under low silicon conditions was studied, And the pellet strength change law was systematically analyzed from the microscopic morphology and structure perspective. The results of the study show that increasing the roasting temperature and alkalinity can effectively improve the compressive strength of pellets. At low SiO₂ content, the pellet ore is mainly cemented by hematite continuous crystals and the change in strength is not obvious. With the increase of alkalinity, the amount of liquid phase of low silicon flux pellets increases during roasting, and the liquid phase of calcium ferrite system with strength higher than hematite eutectic appears, which improves the pellet strength; With the increase of MgO mass fraction, magnesium ferrite increases, which not only inhibits the formation of liquid phase in pellets, but also inhibits the oxidation of magnetite. Because the strength of magnesium ferrite system is greater than that of magnetite and hematite, the pellet strength increases, but too much magnesium ferrite will also affect the liquid phase bonding inside the pellet, lead to structural deterioration and reduce the pellet strength. Therefore, the compressive strength of pellet increases first and then decreases. The above study provides theoretical guidance and reference for the investigation of low-silica magnesia fluxed pellets.

Plug and Play Electrodeposition Cell: A Case Study of Bismuth Ferrite Thin Films for Photoelectrochemical Water Splitting

In the present study, we designed and fabricated a cost-effective miniaturized versatile electrochemical deposition cell, which is found to be at par performance as compared with conventional electrodeposition techniques. A case study is being undertaken for the electrodeposition of varied thicknesses of bismuth ferrite (BiFeO3) films on FTO glass substrates. X-ray diffraction (XRD) patterns confirm the structural perovskite phase of BiFeO3 (BFO). UV–visible absorption spectra and Tauc plot of BFO estimate the direct band gap which lies between 1.9 to 2.1 eV. The properties of the bismuth ferrite crystal system such as electronic band structure and density of states (DOS) are investigated theoretically. Photoelectrochemical (PEC) water splitting application is carried out to investigate the best performance of BFO films of varied thicknesses. The best performer (BFO15) working electrode yields a photocurrent density of ∼35 μA cm−2 at 0.2 V vs RHE under visible LED (light intensity of 100 mW cm−2) in neutral 0.5 M Na2SO4 electrolyte. Incident photon to current conversion (IPCE) measurements, electrochemical impedance spectroscopy (EIS), and Mott-Schottky characteristics confirm the best performance of BFO15 photocathode film.

Shielding performance of MnxNi0.8–xZn0.2Fe2O4 (0.1≤x≤0.7) for electromagnetic interference (EMI) in X-band frequency

A series of MnxNi0.8–xZn0.2Fe2O4 (0.1≤x≤0.7) nanoferrites were prepared by sol-gel auto combustion method. The TGA-DSC studies revealed the weight loss up to 700 °C and after no weight loss was found confirming the complete ferrite phase. Therefore, the as-burnt samples subjected to conventional sintering at 900 °C for 2h. The traces of XRD patterns revealed that formation of ferrite phase co-existed with secondary phases. The complex permittivity and permeability of present ferrite systems are found to be dependent of Mn2+ ion concentration. The real part of dielectric constant (ε′) for the all compositions are in the range of 5.184–6.951 at 8.2 GHz while it is 5.269–7.663 at 12.4 GHz. The values of ε′ at 8.2 GHz are slightly lower than the values at 12.4 GHz. The imaginary part of dielectric constant (ε″) was found to be in the range of 0.046–0.315 for all compositions over the entire range of X-band frequency (8.2–12.4 GHz). Compared to the variation of ε′, the variation of ε″ is more disorder. The number of semicircles in Cole-Cole plots is a witness of multiple di-electric relaxations of EM energy dissipation. The real part of magnetic permeability (μ′) is increasing, while imaginary part of magnetic permeability (μ″ ) is decreasing for all compositions as frequency is increasing from 8.2 to 12.4 GHz. Compared to the other ferrite compositions, the ferrite with low content of Mn2+ i.e. Mn0.1Ni0.7Zn0.2Fe2O4 ferrite system has higher value of μ″ and seems to be invariant over the entire X-band frequency range. The total effective shielding (SET) for all compositions is found to be in the range 37–12 dB. The highest values of SET 37 dB at 8.2 GHz and 28 dB at 12.4 GHz were reported for the ferrite composition Mn0.1Ni0.7Zn0.2Fe2O4. The shielding studies revealed that Mn–Ni–Zn ferrite systems are effectively suppressing electromagnetic interference (EMI) in X-band frequency. Comparatively, the ferrite system Mn0.1Ni0.7Zn0.2Fe2O4 is useful for the fabrication of EMI suppressor.

Modulation of magnetoelectric coupling through systematically engineered spin canting in nickel–zinc ferrite

AbstractA nickel–zinc ferrite system, which is one of the well‐known versatile soft‐ferromagnetic oxides, was investigated in terms of magnetoelectric (ME) coupling at room temperature. Herein, we demonstrated that spin canting is manipulated through a composition‐induced structural transition from an inverse to a normal spinel structure, leading to modulation in the ME coupling. The ME coefficient was maximized at 60 at.% Zn substitution with a value of 0.1 mV/(Oe·cm), denoting ∼70% enhancement compared to that of the pure nickel ferrite. It was revealed that the interspin angle is enhanced along the octahedral site at up to ∼60 at.% Zn substitution, consistent with the composition level at the culmination of the ME coupling, evidenced by X‐ray diffraction profiles and magnetic hysteresis loops combined with density functional theory calculations. Given that this approach is based on a tractable fabrication method, this study is expected to be widely used in modulation of the ME coupling in spinel‐structured oxides.

Electrical and Dielectric Studies of the Cd‐Doped Co‐Ni Ferrites Synthesized by Solid State Reaction Method

AbstractThe present study reports the dielectric and DC resistivity studies of the Cd doped Co‐Ni ferrites synthesized by solid state reaction method. The XRD studies confirm the cubic spinel structure of the samples. The substitution of the cadmium in the ferrite system significantly influences the AC conductivity, involvement of the grain boundary involvement in conduction. The variations of dielectric constant and dielectric loss for all the samples are studied as a function of frequency and show an increase with doping concentration. The DC resistivity studies confirm the semiconducting nature of the synthesized ferrites. The activation energy is observed to be in the range of (0.534–0.629 eV).

Impact of Gd3+ and Nd3+ ions substitution on structural and magnetic properties of Co0.5Ni0.5Fe2O4 ferrite system

Co0.5Ni0.5(Gd/Nd)xFe2-xO4 (x ​= ​0.0 and 0.06) ferrites were prepared by the solid-state reaction method. These materials were characterized by XRD, FT-IR spectroscopy, and VSM techniques. The XRD analysis revealed the phase formation of all samples and their cubic spinel structure with the Fd-3m space group. Lattice constant was found to increase due to Gd and Nd ions substitution. However, the crystallite size was observed to decrease by the substitution effect. The FT-IR spectra showed the two vibrational frequency bands of the tetrahedral and octahedral sites. From the magnetic properties study, it was identified that the pure and Gd substituted Co0.5Ni0.5Fe2O4 ferrite showed a ferromagnetic behaviour. While the Nd substituted Co0.5Ni0.5Fe2O4 ferrite delivered a superparamagnetic behaviour. The substitution of Gd and Nd changed the values of the magnetic parameters of Co0.5Ni0.5Fe2O4 ferrite. An increase in the saturation magnetization (Ms) value was observed due to substitution of Gd and Nd in Co0.5Ni0.5Fe2O4 ferrite, indicating that Gd and Nd substitution strengthen the supermagnetic interactions in Co0.5Ni0.5Fe2O4 ferrite. The highest value of Ms was observed in Gd doped sample.

Theoretical Study of the Impedance Matching of the Ferrite Tuner System for ICRF Heating

A theoretical study on a ferrite stub tuner antenna system for ion cyclotron resonance frequency (ICRF) heating is discussed in this paper. High amounts of radio frequency power can be reflected at the antenna as a result of impedance mismatches arising from large changes in the plasma resistance during L- to H-mode transitions or edge localized modes. A fast-response ferrite stub tuner network has been proposed to mitigate these reflections by rapidly varying the impedance to match the rapid load changes on the ICRF antenna. This study numerically shows the influence relationship of the normalized mechanical length and the ratio of the ferrite part of two ferrite stubs on the regulating range of a biasing magnetic field of two stubs. A prematching stub can be used to reduce the standing-wave voltage on the ferrite tuners. The analysis of the ideal position and length of the prestub as well as the distance between the ferrite network and prestub are presented. Numerical simulations demonstrate that selecting ideal values for mechanical length and the ratio of the ferrite part of two ferrite stubs plays an important role in the impedance matching performance of the triple ferrite system during a large variation in plasma resistance.

Dielectric and Magnetic Study of NiCuZn Spinel Ferrites

The ferrite system having spinel structure with composition Ni1-x-yCuxZnyFe2O4; [(x = 0.3, 0.2), (y = 0.2, 0.3, 0.5)] has been amalgamated through solid-state reaction method and structural, dielectric and magnetic studies have been carried out. The Presence of tetrahedral and octahedral bands in FTIR spectra confirmed the proper phase formation of spinel ferrites. In low-frequency region dispersive behaviour has been shown by both dielectric constant (ε′) and tangent loss (tanδ) and they show nearly constant value at higher frequencies. This follows Maxwell-Wagner double layer model in which low conductive grain boundaries separate higher conductivity grains and in good agreement with Koop’s Model. The Nyquist plot shows depressed semi-circular arcs. The ac conductivity (σ ac) shows increasing trend with temperature and frequency both. The S parameter has been calculated from the fitted ac conductivity plot and used to explain conductivity mechanism. The samples show good magnetic behaviour. Maximum value of saturation magnetization has been observed for the sample having the highest Zn content. Magnetization versusTemperature plot implies towards non equilibrium magnetization below its reversibility temperature.

Kruskal’s simplification scheme in ferrite dynamics

In this work, we deal with the dynamics of a ferromagnet slab of zero conductivity under the influence of an external magnetic field and submitted to an electromagnetic wave perturbation as described by coupled complex-valued system equations. As a result, with the aid of the Painlevé analysis, we find that for the above ferrite system to support microwave excitations, the damping factor raised from the Landau–Lifshitz–Gilbert formalism ought to vanish while implying the existence of some set of infinite law of conservations. Following the underlying feature of Kruskal’s approach to generating in a straightforward manner some typical solutions, we henceforth discuss the physical implications of the traveling waveguide excitations.

Investigation on the formation, structural and photocatalytic properties of mixed Mn-Zn ferrites nanoparticles embedded in SiO2 matrix

The structure, morphology and photocatalytic features of the Mn-Zn ferrite nanoparticles embedded in SiO2 matrix produced by a modified sol-gel synthesis were investigated. The synthesis consists of mixing the metal nitrates, 1,4-butanediol and tetraethylorthosilicate, formation of the SiO2 matrix by gelation, formation of the metallic succinate precursors by heating the gel up to 200 °C and formation of the ferrite system by thermal treatment at higher temperatures. The formation of Mn-, Zn- and Fe-succinate precursors up to 200 °C and their decomposition into ferrites up to 400 °C was confirmed both by thermal analysis and Fourier-transform infrared spectroscopy. The X-ray diffraction provided information on the crystalline phases, crystallite size and lattice constant, while the morphology of the samples was investigated by transmission electron microscopy. The crystallite size increased (30.5–53.4 nm), while the energy band gap of the samples decreased (2.09−1.33 eV) with the increase of the Mn content in the ferrite; thus, the amount of manganese nitrate used in the synthesis could be an easy tailoring approach of the mixed Mn-Zn ferrites. All samples showed sonophotocatalytic activity, being able to degrade Rhodamine B under visible light irradiation, Mn0.3Zn0.7Fe2O4@SiO2 sample having the best sonophotocatalytic performance.

Element-specific magnetic hysteresis loops observed in hexagonal ErFeO3 thin films

We investigated the magnetic properties of multiferroic hexagonal ErFeO3 thin films by using x-ray magnetic circular dichroism (XMCD) and synchrotron Mössbauer spectroscopy. In order to reveal the element-specific magnetic properties, temperature-dependent XMCD experiments were conducted at the Fe L 2,3 and Er M 4,5-edges. Apparent magnetic hysteresis loops appear for both ions below the Néel temperature, which suggests the existence of ferromagnetism. The temperature evolutions of the coercive field and spontaneous magnetization for both ions show similar behavior. These results indicate that Fe ions influence the magnetism of Er ions. Our results deepen the understanding of the physical properties of hexagonal rare-earth ferrite system.