Ferrite System Research Articles

Tunability of localization length in naphthalene sulfonic acid doped polyaniline/nickel ferrite composite nanorods system

Tunability of key length scales including nanodimensionality, mean free path, localization length, and cyclotron radius gives opportunities to fabricate nanodevices with new functionalities. Herein, in order to tune localization length, composite nanorods (CNRs) of 2-naphthalene sulfonic acid doped polyaniline (PANI-NSA) and nickel ferrite nanoparticles (NiFe2O4 NPs) are synthesized via an in situ chemical polymerization method. The nanorods’ structure and the incorporation of the NiFe2O4 NPs into the PANI-NSA matrix are envisaged by various characterization techniques. The presence of a hysteresis loop with minor coercivity and remanence suggests the ferrimagnetic property of PANI-NSA/NiFe2O4 CNRs at room temperature. Investigation of electrical resistivity as a function of temperature in the absence of an external magnetic field establishes quasi-one-dimensional variable range hopping conduction mechanism of the PANI-NSA/NiFe2O4 CNR samples. CNR samples with two different loadings of NiFe2O4 NPs demonstrate substantial amounts of magnetoresistance (MR) at all the temperatures (300–50 K) studied. Intriguingly, a transition from positive to negative MR is observed with an increase in temperature from 200 to 300 K for CNR samples with less amount of NiFe2O4 (CNRs 1), whereas MR is positive for CNRs with higher loading of NiFe2O4, throughout the studied temperatures. Positive and negative MR behaviors of the CNR samples are quantitatively elucidated in terms of wave function shrinkage and forward interference models. Deduced localization length from the forward interference regime for CNRs 1 is about one order of magnitude larger than that in the wave function shrinkage regime. Thus, tuning of localization length can be achieved qualitatively through appropriate loading of NiFe2O4 NPs.

Magnetization reversal, magnetic anisotropy and ordering studies on quenched copper-ferri-aluminates

The magnetic properties of thermally quenched spinel ferrite system, CuAlxFe2-xO4 (x = 0.0, 0.2, 0.4 and 0.6), have been investigated by means of DC magnetization, hysteresis loop characteristics and thermal variation of low field ac susceptibility measurements. The system possesses a tetragonally distorted spinel structure and exhibits a non-collinear spin arrangement. The magnetic characteristics suggest that the ferrites are low anisotropy compounds, the negative magnetization observed for x = 0.6 composition at the compensation temperature T = 22 K is due to the copper ion moment with a net effect antiparallel to that of the Fe3+ ions with different temperature dependence giving rise to a compensation effect. The low-temperature anomalies on the zero field cooled curves are due to the coexistence and interplay between the ferrimagnetic long-range ordering and short-range ordering in the system.

Observation of diffusion behavior between Cr2O3 and calcium ferrite based on diffusion couple method at 1373 K

The existence of Cr2O3 has an effect on the quality of high-chromium vanadium-titanium magnetite sinter. In order to investigate the influence of Cr2O3 on the quality of sinter in the solid-phase reaction stage of sintering process, the solid-phase reactions of Cr2O3-calcium ferrite (CF) system at 1373 K in air at different times were studied by diffusion couple method. The change of diffusion interface and the migration of Ca, Cr and Fe were observed by emission scanning electron microscopy. The results show that in the process of diffusion, the diffusion thickness of Ca2+ in CF layer was 10.22 μm, and that of Ca2+ in Cr2O3-CF diffusion couple was 57.65 μm at 1373 K for 8 h. The relationship between the thickness of the product layer and time at 1373 K for 0 h–20 h was obtained. The diffusion of Ca2+ to the Cr2O3 layer is the driving force of the solid phase reaction, and the diffusion of Ca2+ in the ferrite layer is the limiting link of the solid phase reaction, the order of magnitude of diffusion coefficient of Cr2O3-CF diffusion couple was 10−11 cm2 s−1. Ca2+ in calcium ferrite is likely to combine with Cr3+ to form CaCr2O4. The production of calcium ferrite will be reduced when Cr2O3 is present in sintering material. Meanwhile, the solid phase product CaCr2O4 in the diffusion process has the properties of high melting point and difficult reduction. The shortage of liquid phase due to high melting point and the difficulty in reduction may affect the quality of sinter.

Superparamagnetic Behavior at Room Temperature through Crystal Chemistry Modification and Particle Assembly Formation: Zinc and Nickel Ferrite Systems

Zinc and nickel ferrites were prepared through a solvothermal method with different microstructures: as assemblies of particles and not forming assemblies. By means of Raman spectroscopy, the catio...

Sonochemical Synthesis of CoFe2-xNdxO4 Nanoparticles: Structural, Optical, and Magnetic Investigation

This investigation deals with CoFe2-xNdxO4 (x ≤ 0.2) nanoparticles (NPs) fabricated by sonochemically. The purity of all products was verified via X-ray powder diffraction. The crystallite size of the samples was calculated as less 12 nm. The spectral analyses also confirmed the presence of spinel ferrites. Both morphology and chemical purity of the spinel ferrite systems were confirmed by SEM, EDX, and elemental mapping analyses. The analyses of magnetization versus applied magnetic field, M(H), were performed. The following magnetic parameters like saturation magnetization Ms, squareness ratio (SQR = Mr / Ms), magnetic moment nB, coercivity Hc, and remanence Mr have been evaluated. The M(H) curves revealed the soft ferromagnetic nature for all CoFe2-xNdxO4 NPs. It is showed that the Nd3+ substitutions significantly affect the magnetization data. A decreasing trend in the Hc, Ms, nB, and Mr values was detected with Nd3+ substitution.

Cerium doped MgFe2O4 nanocomposites: highly sensitive and fast response-recoverable acetone gas sensor

We report a facile synthesis of Cerium doped MgFe2O4 nanocomposite ferrite and its usability as gas-sensor via simple and robust synthesis approach of glycine-combustion-process. The route utilizes metal nitrates (Ce, Mg, Fe -nitrates) and glycine, in aqueous solution. The involved sol-gel concept was explained on the basis of zwitterion characteristic of glycine. The analysis of the developed ferrite was done in two different ways – i) effect of Ce-doping concentration, and ii) effect of sintering temperature. With the ferrite system MgFe2-xCexO4, the doping concentration of Ce was varied from 0.04 to 0.12 with the step x = 0.04, and sintering was done at two different temperatures i.e. 973K and 1173K. As-produced composite system was examined for their gas response towards reducing gases such as LPG, ethanol, acetone and ammonia. The material displayed excellent gas sensing properties towards acetone for wide operating temperature range of 575–675 K. The XRD analysis revealed nanocrystallinity with crystallite size in the range of 28–34 nm. Microstructural analysis confirmed the porous morphology due to auto-ignition during the combustion reaction. The present investigations confirm the produced MgFe2-xCexO4 is a promising candidate for fabricating high performance acetone sensor.

Structural, morphological and optomagnetic properties of GO/Nd/Cu-Mn ferrite ternary nanocomposite

Graphene oxide (GO)/neodymium (Nd)/Cu 0·5 Mn 0·5 Fe 2 O 4 ternary nanocomposite was prepared by sonochemical method and modified Hummer's method. The crystal structure and structural parameter of Cu 0·5 Mn 0·5 Fe 2 O 4 (CMF) nanoferrites were changed with the addition of Nd 3+ and GO. Raman active modes of the GO and ferrite system were observed from Raman spectra. The surface oxidation state (C 1s, O 1s, Cu 2p, Mn 2p, Fe 2p, and Nd 3 d) and their respective binding energies of the prepared nanocomposite were discussed. Different surface morphologies were acquired for CMF, Cu 0·5 Mn 0·5 Fe 1.85 Nd 0.15 O 4 (CMNF), GO, and GO/Cu 0·5 Mn 0·5 Fe 1.85 Nd 0.15 O 4 (GCMNF) ferrite nanocomposites. The absorption of the Cu-Mn nanoferrite (red region) shifted into the blue region with the addition of Nd 3+ and GO. The magnetic parameters were changed with doping of Nd into CMF and GO in CMNF nanoferrite. It was found that the high anisotropy energy values of the CMNF and GCMNF ferrite nanocomposites could be used for electromagnetic wave-absorbing application.

The influence of reagents ball milling on the lithium ferrite formation

In this work, the effect of ball milling of Li2CO3 and Fe2O3 reagents on the Li0.5Fe2.5O4 ferrite formation was studied by thermogravimetric and differential scanning calorimetric measurements using non-isothermal heating and cooling modes. In the latter case, the analysis was carried out with a magnetic field applied in order to estimate the Curie temperature of the synthesized ferrite. The mechanical milling of both individual Li2CO3/Fe2O3 reagents and their mixture was performed with an AGO-2C planetary mill using steel vials and balls. Samples with different bulk densities, which were compacted from non-milled and milled powders by pressing with different compaction pressures, were investigated. The results showed that the mechanical milling of powder reagents separately does not cause a significant change in the reactivity of the ferrite system. Only milling of the Li2CO3/Fe2O3 mixture makes it possible not only to increase the reactivity of powders, but also to exclude additional compaction of samples before synthesis.

Influence of manganese on multiferroic and electrical properties of lanthanum ferrite nanoparticles

In the present work, we have successfully prepared pure and Manganese (Mn) doped single phase nanocrystalline LaFeO3 by using an auto combustion route. X-ray diffraction (XRD) study ensures the purity of phase whereas the transmission electron microscope (TEM) measurement confirms the nanocrystalline nature. The details of the DC and AC conduction mechanism are studied to illustrate the dielectric behavior and charge transfer mechanism. The DC resistivity increases with the doping concentration which has been illustrated by Mott’s variable range hopping (VRH) model. The AC conductivity mechanism as a function of frequency (20Hz ≤ f ≤ 1MHz) and temperature (303K ≤ T ≤ 573K) is explained by correlated barrier hopping (CBH) model. The dielectric constant and activation energy (AC) increase with Mn concentration whereas dielectric loss decreases. So, the leakage behavior decreases within the samples. The XPS spectra confirm that there is a rise of Fe2+ and Mn4+ ions in the samples with the doping concentration which may be responsible for the enhancement in magnetization. Mixed ferromagnetic (ferromagnetic and antiferromagnetic) order exists within the samples. As a result exchange bias arises. We have achieved the highest value of the coercive field (2.5 kOe) in Mn doped LaFeO3 system. The room temperature ferroelectric and magnetodielectric measurements indicate that the polarization and magnetodielectric coefficient increases significantly by virtue of Mn doping. Therefore, an enhancement of multiferroic and magnetodielectric properties has been achieved for chemically prepared nanocrystalline lanthanum ferrite (LaFeO3) system by virtue of Mn doping. All the observations indicate that these materials to be potential candidates in the emerging field of spintronics.

High performance ternary polyaniline-acetylene black-cobalt ferrite hybrid system for supercapacitor electrodes

A novel ternary polyaniline-acetylene black-cobalt ferrite hybrid system was synthesized and confirmed by XRD, FTIR, UV, SEM, EDS analysis. Ternary composite electrode (PACOF) and the corresponding symmetric supercapacitor had high specific capacitance of 747.64 and 282.35 F/g, respectively at 1 mA. The ternary electrode based symmetric system had 39.218 Wh/kg and 3042.77 W/kg of specific energy and specific power, respectively. The ternary system has the least charge transfer resistance value of 2.3 Ω. Ternary hybrid system has the highest specific capacitance retention (81%) after 6000 cycles. The superior performance of ternary composite was due to the synergistic effects between individual components.

Structural and magnetic properties of CuFe2O4 ferrite nanoparticles synthesized by cow urine assisted combustion method

Abstract Copper ferrite (CuFe2O4) nanoparticles were synthesized by sol–gel auto combustion method using cow-urine as a chelating agent. The obtained ferrite nanoparticles are heat treated at different temperatures (450 °C and 750 °C) in order to study their size dependent structural and magnetic properties. Energy Dispersive X-ray (EDX) spectra showed the maintenance of stoichiometry of elemental composition of ferrite system. Secondary phases of CuO and α-Fe2O3 are identified from the X-ray diffraction (XRD) patterns and these phases seem to be reducing with the heat treatment improving the ferrite phase of the sample. A systematic variation of structural parameters that is decrease of lattice parameter (8.379–8.369 A) and increase in average crystallite size (13.7–18.2 nm) have been found with the heat treatment. The average particle size estimated from Field Emission Scanning Electron Microscopy (FE-SEM) micrographs (14.5–22.3 nm) is slightly bigger than the average crystallite size estimated from XRD is due to the coalescence of crystallites which can be identified in FE-SEM micrographs. The obtained vibrational frequencies in the range of 550–450 cm−1 confirm the ferrite phase of copper ferrite. The splitting observed at the octahedral vibrational band is assigned to the secondary phase of α-Fe2O3. The saturation magnetization (Ms) is increasing with the heat treatment and highest value of Ms = 35.4 emu/g was reported. The results are discussed in terms of variation of particle sizes presuming the core–shell interactions.

Estimation of structural composition of the inverse spinel ferrites using 57Fe-Zero Field Nuclear Magnetic Resonance

We have demonstrated 57Fe Zero Field Nuclear Magnetic Resonance (ZFNMR) as a powerful tool in determining the structural composition of nickel-cadmium spinel ferrites of various compositions of Ni1-x Cdx Fe2O4 from x = 0 to1, which are synthesized via one-step auto combustion technique. The XRD measurements confirm the phase purity of all the samples. Vibrating Sample Magnetometry (VSM) measurements show that saturation magnetization (MS) increases initially (up to x = 0.3) and then decreases for higher concentrations of cadmium. The Fe3+ ions in the inverted spinel ferrite distribute equally among two possible sites (tetrahedral A and octahedral B) with different hyperfine fields. Therefore for x = 0 under the assumption that Ni enters B sites, 57Fe NMR of Fe3+ ions yield two signals of equal integral intensities in spectral lines corresponding to these sites. Thus, for the sample series Ni1-x Cdx Fe2O4, the contribution of Fe3+ nuclei varies for A and B sub-spectra with the substitution of a non-magnetic Cd2+ ion. By measuring the Fe3+ distribution on A and B sites which is determined from relative spectral areas of A and B NMR sub-spectra the cation distribution is estimated and has been verified by the binomial distribution. Further, XRD Rietveld refinement results are also in good agreement with the composition estimated by NMR technique and the ideal composition. We have demonstrated the usefulness of NMR technique to quantify the accurate composition of the mixed spinel ferrite systems using Ni-Cd ferrite as a test case. Further, the estimated inversion parameter (at around x = 0.4), for the studied system, obtained from ZFNMR, XRD, and VSM techniques are in excellent agreement with each other.

Precise Vehicle Location Detection Method Using a Wireless Power Transfer (WPT) System

The paper proposes a method for locating an electric means of transportation such as electric vehicles that adopts dynamic wireless charging system. The method works with magnetic wireless power transfer systems, based on a ferrite core counting approach. The ferrite core counter system operates by counting all the ferrite cores of the source coils used for guiding the magnetic field in a magnetic wireless power transfer system. The proposed ferrite core counter has a position detection accuracy equivalent to the spacing of the ferrite cores. In addition, this paper proposes a ferrite position identification (FPID) messaging unit to correct ferrite core counter errors. FPID blocks which are successively placed under the source coil are recognized by the ferrite core counter, and their passage is reported as a sort of message in the vehicle. This FPID messaging unit provides the ferrite core counter with a system that can correct errors in the number of ferrite cores counted. The effectiveness of the vehicle positioning system with the ferrite core counter and the FPID messaging unit has been demonstrated through simulation and experiments.

Coaxial-Nanocable Structured MnFe2O4 Based on Polydopamine-Modified MWCNT for Anode Materials of Lithium-Ion Batteries

Energy storage technology for lithium-ion batteries (LIBs) has made rapid progress, and has been applied in a wide range of applications such as portable electric devices, hybrid electric vehicles (HEVs) or electric vehicles (EVs) even in large-scale energy storage system (ESS). Nevertheless, the electrode materials still require the enhancement on its energy or power densities for satisfying the needs of global market. Meanwhile, research on high-capacity anode materials beyond the low theoretical capacity limit of 372 mA h g-1 of commercialized graphite materials is performed actively in numerous research groups. As one of the alternative candidates, transition metal oxides have strong advantages, which can substitute the graphite materials, such as high theoretical capacity (≥500 mA h g-1), earth abundant and simple preparation process. However, the charge/discharge process of “conversion reaction”, which is typically shown in oxide-based anode materials, causes lower cyclability resulted by repetitive volume change in the reaction process. Also, oxide materials generally exhibit lower electrical conductivity than carbon or metal-based anode materials. Recently, metal ferrites (MFe2O4, M = Mn, Co, Ni, Zn) show higher level of electric conductivity and chemical stability from the modified electronic structure which is resulted by doping of foreign metal atoms. Among the various metal ferrites, MnFe2O4 is attractive anode material, because it shows high theoretical capacity of 917 mA h g-1, and it consists of low cost Mn, Fe elements. In our work, to compensate for the limitations of oxide materials using MnFe2O4 nanoparticles, we have introduced two representative technologies of nano-structuring and carbon composite to improve the rate capability and cycle performance of the ferrite system. In particular, we also have introduced polydopramine (PDA) coating technique using versatile properties of the polydopamine such as high hydrophilicity and adhesive ability from rich functional groups (e.g. –OH catechol, –NH2 amine). Mussel-inspired PDA is well known as its strong adhesion to organic/inorganic surfaces, good environmental stability, biocompatibility, and excellent dispersibility in water. In this regard, we applied the PDA coating layer to carbon nanotubes (CNTs) to mitigate the strong inner-tube van der Waals interactions, and it helps to fabricate coaxial nanocable structures with increased dispersibility in the precursor solution of the MnFe2O4. In our process, metal ions in the solution are attracted by –OH catechol groups in PDA layer, and MnFe2O4 nanoparticles are co-precipitated at low temperature (98 oC) around CNT surfaces. Eventually, the nanoparticles are attached on the CNT by PDA layer. As a result, well defined coaxial nanocable structures, which is composed of MnFe2O4 nanoparticles and CNT core, were successfully prepared without a particle aggregation after our synthesis process. These coaxial nanocable anode materials effectively supply electrons through the CNT core with well contacted MnFe2O4 nanoparticles on the surface by the aid of the strong adhesive ability of the polydopamine coating layer. Besides, increased surface area for a facile electrolyte penetration provides better Li+ ion kinetics with an enhanced ionic conductivity. Furthermore, homogeneous CNT matrix can accommodate volume changes in the repetitive conversion reaction, and improves the cyclic stability of anode materials.

Synthesis of polymer composite based on polyaniline-acetylene black-copper ferrite for supercapacitor electrodes

A totally new hybrid ternary (polyaniline-acetylene black-copper ferrite) system reported in the present work. The formation of materials was confirmed by XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), UV (Ultra-violet spectroscopy), SEM (Scanning electron microscopy), and EDS (Energy dispersive x-ray spectroscopy) analysis. The interconnected structure of ternary system favored different electrochemical activities. Ternary PACF electrode showed the highest specific capacitance of 732.35 F/g at 0.5 A/g. Symmetric supercapacitor fabricated using hybrid PACF electrode exhibited a specific capacitance of 192.64 F/g at 0.5 A/g. The obtained specific energy and specific power of ternary hybrid system were 26.757 Wh/kg and 3165.25 W/kg, respectively. Ternary composite provides fascinating results due to the synergistic effects between individual components and can be used successfully in the field of supercapacitors. EIS analysis was carried out to obtain the resistances of electrode material.

XRD, EDX, FTIR and ESR spectroscopic studies of co-precipitated Mn–substituted Zn–ferrite nanoparticles

Co-precipitation synthesizing technique was adopted to prepare manganese doped zinc ferrite nanoparticles with varying concentrations 0.5, 0.6, 0.7. EDX proved the consistency of stoichiometry of compositions in the ferrite samples considered under preparation. XRD patterns authenticated the ferrite phase in the investigating samples. The experimental lattice parameter (8.412–8.438 Å) is increasing and crystallite size (7.6–6.4 nm) appears to be decreasing with substitution of Mn2+. The grain size (1.1 µm) in the sample (x = 0.7) with smaller crystallites (6.4 nm) is found to be bigger than that of remaining compositions (x = 0.5, 0.6). The vibrational frequencies detected in the FTIR spectra also authorized the obtained spinel phase in the current ferrite systems. The elastic moduli illustrate the mechanical strength of ferrite systems which are dependent on interatomic distances. The variation of line width and Lande's g–factor in ESR studies revealed the possibility of core-shell morphology of present ferrite nanoparticles.

Ferrite Position Identification System Operating With Wireless Power Transfer for Intelligent Train Position Detection

Wireless power transfer (WPT) is being developed to supply electric power to electric trains, using a source coil in/on the railway track and a pick-up coil on the train. A number of benefits can be obtained by eliminating the catenary and pantograph currently used for railway electric power supply. However, the WPT employs coils, and the electromagnetic field generated by the WPT can interfere with conventional train detection methods, such as track circuits and RFID, installed on the tracks. Train position information is critical for railway operation, especially for high speed trains. This paper proposes a novel system which provides train position information using a source coil segment. It consists of onboard sensor coils, ferrite blocks designed using specific position information, and a detector. The proposed system can be implemented using the source coil and load coil of the WPT. Information about the train's relative position is obtained by the detection of ferrite blocks distributed within the source coil segment. The train position information provided by the ferrite components is detected by onboard sensor coils and a detector. The proposed ferrite position identification (FPID) system provides accurate train position information and is not affected by WPT electromagnetic interference. The operating principles of the FPID system are presented in detail. The performance of the proposed FPID system was measured by simulations and experiments.

Observation of anomalous site occupancy in Ni-Co-Cu-Cr ferrite system synthesized by sol-gel method

Anomalous variation in cation distribution in chromium doped Ni-Co-Cu-Cr ferrites synthesized by sol-gel method has been observed the formation of spinel structure and explained with the help of DTA/TG and X-ray diffraction analysis. Error estimated between theoretical and calculated lattice parameter based on proposed cation distribution is found be in range of 0.0014% to 0.00005%, which confirms the cation distribution predicted for the present samples. In this present work, it appears that most of the cobalt and 50% of nickel ions are observed to occupy A-sites instead of B-sites of spinel lattice, which is a drastic deviation from the reports published till date. The g-value have been found to be lower for x = 0.02 concentration as observed from ESR analysis. Fourier transform infrared spectroscopic techniques (FTIR) show no variation in peak position of vibrational bands, indicates the uniform bond length in the spinel ferrite, even for different concentration of chromium. This is further confirmed by the bond length calculation using empirical formulas and experimental lattice parameters, showing least error for shared and unshared ion for tetrahedral or octahedral sites.

Structural, optical and vibrational study of zinc copper ferrite nanocomposite prepared by exploding wire technique

Abstract We have synthesized zinc-copper ferrite (ZCFO) employing exploding wire technique (EWT). The X-ray diffraction (XRD) data confirm the formation of single phase spinel ZCFO, which is in good agreement with Fourier transform infrared spectroscopy (FT-IR), UV-Vis, and Raman spectroscopic analyses. It is also clearly seen in the SEM micrographs that the grains in ZCFO ferrite are very rough, which allows adsorption of gas like oxygen and therefore, the material can behave as active sensing surface. The size range of the grains in prepared sample is of 200 nm to 500 nm. The FT-IR spectrum of the nanocomposite consists of two broad bands, one at 580.4 cm−1 due to M–O stretching mode at the tetrahedral site and the other at 400.7 cm−1 due to M–O stretching mode at the octahedral site. The nanoparticles show a UV-Vis absorption band in the wavelength region of 400 nm to 700 nm. The energy band gap for the prepared nanomaterial was estimated to be 3.16 eV. Thus, the ferrite nanocomposite prepared by EWT is optically active. According to present literature, Raman spectroscopy study on zinc-copper ferrite system has not been reported till date. By suitable attributing various Raman modes, we have further confirmed the formation of ZCFO nanophase through the present novel approach.

The influence of selected ions on various characteristics of Nickel-Zinc ferrites

Abstract One of acknowledged methods remarkably improving structural, magnetic and electrical properties of spinel ferrite systems is the substitution of iron ions by some trivalent ions. In the family of spinel ferrites, thanks to its high saturation magnetization and electrical resistivity as well as low losses, the nickel-zinc ferrite is a very important magnetic material used in many applications in electrical engineering and electronics. The properties of these materials are in general dependent upon chemical composition, method of preparation, stoichiometry, sintering time, temperature as well as the atmosphere, etc. In this study the influence of appropriately selected ions (M = In3+, Nd3+, Dy3+ and Er3+), partly replacing Fe3+, on the microstructure and magnetic properties of spinel ferrite with the composition Ni0.42Zn0.58M0.02Fe1.98O4 fabricated by means of standard ceramic technology was investigated.