Electrical and magnetic properties of BaTiO3−(Ni0.3Zn0.7)Fe2.1O4 composites

Ceramic composites consisting of ferroelectric and ferrite ( were synthesized by the mixed oxide route. The phase assemblage, electrical and magnetic properties of the samples were investigated. The results indicates that the phase is compatible with ( phase, and dense diphasic composite ceramics were obtained. Electrical resistivity of composites varies with increasing amounts of ( phase, and shows a percolation-like drop. Magnetic hysteresis loops were observed in the composites.     

Structural,dielectric, magnetic,and optical properties of Ni0.75Zn0.25Fe2O4–BiFeO3 composites

The magnetoelectric composites of spinel ferrite Ni_0.75Zn_0.25Fe₂O₄ (NZF) and BiFeO₃ (BFO) with general formula xNi_0.75Zn_0.25Fe₂O₄ + (1 ? x)BiFeO₃ (x = 0, 0.10, 0.20, and 0.30) have been prepared via hybrid processing route. Subsequently, the effects of addition of NZF on structural, dielectric, magnetic, magnetoelectric, and optical properties of BFO have been investigated, and significant enhancements have been observed in physical observables such as grain size, dielectric constant, magnetization, and polarization in ferroelectric hysteresis loops. The variation of magnetization with temperature indicates the presence of spin glass behavior along with the ferromagnetic component. The magnetoelectric coupling is found with a value of magnetocapacitance to be 4.6 % for 30 mol% addition of NZF. The optical properties of the composites are also studied using UV–Vis diffuse reflectance spectroscopy, Photoluminescence spectroscopy, and FTIR spectroscopy.     

A study of structural, ferroelectric, ferromagnetic, dielectric properties of NiFe2O4–BaTiO3 multiferroic composites

The mixed spinel-perovskite multiferroic composites of xNiFe₂O₄-(1 ? x)BaTiO₃ (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) have been prepared by sol–gel method. The structure and morphology of the composites were examined by means of X-ray diffraction and transmission electron microscope. High-resolution transmission electron microscope image indicates a clear view of ferrite and ferroelectric phase. Moreover, we observed a fine interface between the two phases, where the coupling effect of ferrite and ferroelectric phase happened. The composites show excellent ferromagnetic and ferroelectric properties. The saturation magnetization (M_s) reaches to 24.139 emu/g for x = 0.6 at room temperature, the magnetization is about 2.37 emu/g for x = 0.6 when the temperature decreases to 90 k, and the polarization reaches to 3.75 μC/cm² for x = 0.1. Frequency dependent variations of dielectric constant and loss tangent for xNiFe₂O₄-(1 ? x)BaTiO₃ were studied in detail.     

Studies on magnetic and magnetoelectric properties of the NiFe2O4–Ba0.7Sr0.3TiO3 composites

The magnetic and magnetoelectric properties of magnetoelectric (ME) composites consisting of with nickel ferrite (NiFe₂O₄) and barium strontium titanate (Ba_0.7Sr_0.3TiO₃) were investigated. The composites were prepared by standard double sintering ceramic method. The X-ray diffraction analysis was carried out to confirm the phases formed during sintering and also to calculate the lattice parameters. The hysteresis measurements were done to determine saturation magnetization (M_s), remenance magnetization (M_r) and coercivity (H_c) of the samples. The magnetoelectric voltage coefficient (dE/dH)_H was studied as a function of intensity of the magnetic field. The measured magnetoelectric (ME) response demonstrated strong dependence on the volume fraction of NiFe₂O₄ and the applied magnetic field. A large ME voltage coefficient of about 560 μVcm⁻¹Oe⁻¹ was observed for 15% NiFe₂O₄ + 85% Ba_0.7Sr_0.3TiO₃ composite.     

The effect of zinc doping on the structural and magnetic properties of Ni1−x Zn x Fe2O4

Nanoparticles of Ni_1?x Zn _x Fe₂O₄ (x = 0.0, 0.1, 0.3, 0.5, 0.7, and 1.0) were synthesized by the sol–gel auto-combustion method using ethylenediamine tetra acetic acid as a complexion agent. The detailed analysis of X-ray diffraction revealed that the crystalline structure was cubic spinel and by increasing x, it underwent a phase transition from normal to inverse spinel. The crystal lattice constant was increased gradually with increasing zinc substitution from 0.8339 nm (x = 0.0) to 0.8443 nm (x = 1.0). Also, the average crystallite size, which is determined from Scherrer formula, was about 14–35 nm. The spinel phase formation was further monitored by the FTIR analysis. The vibration sample magnetometer data showed that by increasing Zn doping level up to x = 0.3, the magnetization was increased and it was decreased by further increase in x. This effect was discussed by metal cations distribution into the tetrahedral and octahedral sites. Also, the coercivity was decreased by increasing Zn content due to the decrease of magnetocrystalline anisotropy constant of the samples.     

Dielectric and magnetoelectric properties of co-fired PbZr0.52Ti0.48O3–Co0.6Zn0.4Mn0.3Fe1.7O4–PbZr0.52Ti0.48O3 trilayer composites

In this paper we report the dielectric and magnetoelectric (ME) properties of co-fired Pb_0.52Ti_0.48O₃–Co_0.6Zn_0.4Mn_0.3Fe_1.7O₄–PbZr_0.52Ti_0.48O₃ (PZT–CZFMO–PZT) trilayer composites prepared using Mn and Zn simultaneously substituted CoFe₂O₄ (Co_0.6Zn_0.4Mn_0.3Fe_1.7O₄) as a magnetostrictive phase. For PZT–CZFMO–PZT composites, the maximum values of longitudinal and transverse ME voltage coefficient (α _E33 and α _E31 ) were observed to be comparable in magnitude contrary to the usual trend (α _E31 much greater than α _E33 ) for ME composite structures. The highest transverse ME voltage coefficient α _E31 ~64 mV/cm Oe (at an applied ac magnetic field of frequency ~1 kHz) was obtained for the composite containing the thickest layer of CZFMO. The dielectric constant spectra for PZT–CZFMO–PZT composites demonstrated very high values of resonance frequency (~47–81 MHz) and band width (~9–13 MHz).     

Structural,spectral, dielectric,and magnetic properties of indium substituted Cu0.5Zn0.5Fe2−xO4 magnetic oxides

Journal of Materials Science: Materials in Electronics - The influence of indium on the properties of Cu0.5Zn0.5Fe2O4 nano ferrites synthesized by sol–gel auto-combustion technique was...     

Magnetodielectric effect in Ni0∙5Zn0∙5Fe2O4–BaTiO3 nanocomposites

Composites comprising of nanoparticles of Ni_0?5Zn_0?5Fe₂O₄ (NZF) and BaTiO₃ (BT), respectively were synthesized by a chemical method. The particles had diameters in the range of 15–31 nm. NZF was prepared by a coprecipitation technique. This was soaked in a sol containing BT. Compositions synthesized were xNZF-(1 – x) BT, where x = 0?7, 0?5 and 0?3, respectively. The composites showed ferromagnetic hysteresis loops due to NZF phase. The analysis of coercivity variation as a function of temperature gave blocking temperatures in the range of 306–384 K depending on the diameter of the ferrite nanoparticles. This implied that superparamagnetic interactions are above these temperatures. The nanocomposites also exhibited ferroelectric behaviour arising due to the presence of BT. The remanent polarization of the samples was small. This was adduced to the nanosize of BT. The specimens showed magneto-dielectric (MD) effect in the magnetic field range 0–0?7 Tesla. The MD parameter measured at the maximum magnetic field was around 2%. This was one order of magnitude higher than that reported so far in similar composite systems. This was explained on the basis of a two-phase inhomogeneous medium model with an interface between them, the phases possessing drastically different electrical conductivities.     

Effect of Zn doping on structural,magnetic and dielectric properties of LaFeO3 synthesized through sol–gel auto-combustion process

We have studied the structural and dielectric properties of nano-crystalline LaFe_1−xZn_xO₃ (0 ≤ x ≤ 0.3) pervoskite samples synthesized through sol–gel auto-combustion technique. X-ray diffraction and FTIR spectroscopy are used to confirm the single phase characteristics. Microstructural features are investigated using scanning electron microscope and compositional analysis is performed through energy dispersive spectroscopy. The average grain sizes, calculated from the Scherrer formula, lie in the range below 30 nm. The hysteresis (M-H) curves display a weak magnetic order and a shift in the hysteresis loops. Dielectric response has been discussed, in the framework of “universal dielectric response” model. The value of dielectric constant (ɛ′) increases drastically on Zn doping. The dielectric loss factor (ɛ″) shows Debye like dipolar relaxation behavior. The observed peaks in loss factor (ɛ″) are attributed to the fact that a strong correlation between the conduction mechanism and the dielectric behavior exists in ferrites.     

Microstructure, electrical and dielectric properties, and impulse clamping characteristics of ZnO–V2O5–Mn3O4 semiconducting ceramics modified with Er2O3

This study focuses on the effect of Er₂O₃ on microstructure, electrical and dielectric properties, and impulse clamping characteristics of the ZnO–V₂O₅–Mn₃O₄ varistor ceramics. Analysis of the microstructure indicated that the ZnO–V₂O₅–Mn₃O₄–Er₂O₃ ceramics consisted of major ZnO grain and minor secondary phases such as Zn₃(VO₄)₂, ZnV₂O₄, ErVO₄, and VO₂. As the amount of Er₂O₃ increased, the densities of sintered pellets increased from 5.46 to 5.52 g/cm³, whereas the average grain size decreased from 7.2 to 6.0 μm. The breakdown field increased from 1,016 to 3,185 V/cm with an increase in the amount of Er₂O₃. The highest nonlinear coefficient was obtained at the varistor modified with 0.1 mol%, reaching α = 30. The clamp voltage ratio (K), which indicates an impulse absorption capability, was improved with an increase in the amount of Er₂O₃ and the varistor modified with 0.25 mol% exhibited the best K = 2.41.     

M?ssbauer and Magnetic Studies of Co0.5Mn0.5Fe2O4 and Mn0.1Mg0.2Co0.7 Fe2O4 Nanoferrites

We report the magnetic properties of Mn_0.5Co_0.5Fe₂O₄ and Mn_0.1Mg_0.2Co_0.7Fe₂O₄ nanoferrites. The compounds were synthesized by a glycol-thermal method with average particle sizes of about 13?nm and 8?nm, respectively. The M?ssbauer measurements were done at 300?K. The distribution of cations between tetrahedral?(A) and octahedral?(B) sites is investigated. The M?ssbauer spectra indicate ferrimagnetic behavior of the compound. Field cooled (FC) and zero field cooled (ZFC) magnetizations were performed by a Superconducting Quantum Interference Device (SQUID) magnetometer from 4?C380?K. Variation of the magnetizations with the applied fields (up to 50 kOe) were recorded at isothermal temperatures 4, 50, 100, 200 and 300?K. An increase in FC magnetization is observed with increasing applied field. This is explained based on superparamagnetic behavior of the particles.     

Studies of structural and magnetic properties of sol–gel synthesized cobalt substituted Zn–Mn chromites

Cobalt substituted Zn–Mn chromites Zn_1?xCo_xMnCrO₄ (0 ≤ x ≤ 1) were prepared by sol–gel method. The synthesized material was characterized by various physico-chemical methods. The temperature of decomposition, crystallization and phase transformation of the as-prepared powder was studied using TGA–DTA measurement. X-ray diffraction patterns revealed that all compositions are in single phase cubic structure. An infra-red spectral study shows two strong bands, which is attributed to the intrinsic vibrations of tetrahedral sites and the octahedral sites. Formation of spherical particles was revealed by scanning electron microscopy analysis. The elemental analysis as obtained from energy dispersive analysis of X-ray is in close agreement with the expected composition from the stoichiometry of reactant solutions used. Magnetic properties were measured by vibrating sample magnetometer. All the compositions indicated ferrimagnetic nature. The substitution of cobalt ions in the lattice affected the structural as well as magnetic properties of spinel.