Ac Resistivity Research Articles

Structural, micro-structural and physico-chemical studies of Polyvinylpyroledene (PVP) added Cobalt ferrite (CoFe2O4) nanoparticles

To understand the structural and physico-chemical behavior of magnetic nanoparticle (CoFe2O4) is necessary for the selection of materials for various technological applications. The structural parameters derived from X-Ray diffraction (XRD) such as hopping length of site A (LA) and site B (LB), bond length between two A sites (dLA), two B sites (dLB), A and B (dLAB) and some related lengths. The micro-structural and magnetic studies from Fourier transform infrared spectroscopy (FTIR) and vibration sample magnetometer (VSM) analysis such as force constant, bond lengths between cation – anion (p, q, r, s) and cation - cation (b, c, d, e, f), and the angles between the bonds (θ1, θ2, θ3, θ4, θ5) values and trends were studied and it is merely suitable for 7.5 and 12.5 %. In addition some mechanical behavior obtained through their stiff constant C11 and C12 such as Young's modulus, bulk modulus, rigidity modulus and etc., The dielectric and electrochemical behavior of CoFe2O4 measured through AC conductivity (σAC), resistivity (ρAC) and electric modulus (M’, M’’ and M*) electrochemical parameters (V/I, impedance) through LCR and Cyclic voltameter measurements. The obtained results were interpreted and discussed extensively.

Bi3+ doped nanocrystalline Ni–Co–Zn spinel ferrites: Tuning of physical, electrical, dielectric and magnetic properties for advanced spintronics applications

This study reports the synthesis and characterization of nanocrystalline Ni0.5Co0.2Zn0.3BixFe2-xO4 (x = 0.00, 0.025, 0.050, 0.075, 0.100) ferrites synthesized via the sol-gel auto combustion method. The structural, morphological, electric, dielectric, and magnetic properties of Bi3+-doped Ni–Co–Zn spinel ferrites annealed at 700 °C and further sintered at 850 °C, have been investigated towards analyzing the effect of Bi3+ doping. X-ray diffraction (XRD) patterns and Fourier Transform Infrared Spectroscopy (FTIR) spectra have revealed the single-phase cubic-spinel structure of all inspected materials while retaining their high crystalline nature. Their average crystallite size and average grain size are found in the nanoscale range (48–74 nm) and (46–67 nm), respectively. The saturation magnetization (Ms) and experimental magnetic moment (ηexp) are found to decrease with increasing Bi3+ content. The samples sintered at 850 °C display higher AC resistivity, attributing to the reduction of electrons hopping through grains in the samples. The low coercivity values (23.68–87.71 Oe) are observed, classifying the investigated materials as soft ferromagnetic. The increased magnetic anisotropy (K) through Bi3+ doping indicates tunable stability in magnetic orientations, making them suitable for spintronics applications.

Dispersion effect of nano-structure pyrolytic carbon on mechanical, electrical, and microstructural characteristics of cement mortar composite

ABSTRACT In material science, converting waste into nanomaterials by green technologies highlights the interest in producing sustainable carbon nanomaterial (SCN). This study first-ever utilized tyre-char as a Nano-Structure Pyrolytic Carbon (NSPC) to develop electrically conductive composites. Unlike other carbon nanomaterials, the efficiency of NSPC particle as an SCN in developing electrically conductive composites was investigated in terms of dispersion, mechanical, water absorption, electrical resistivity, and microstructure. The results of sedimentation and zeta potential (−19 mV) showed the excellent dispersion of NSPC particle in water with the combined effect of superplasticizer and ultrasonication. The compressive (40.37%) and flexural strength (10.76%) than that of plain cement mortar composite (CMC) is achieved with 2 wt.% and 1.5 wt.% of NSPC particle, respectively. The water absorption rate and volume of permeable voids were reduced, exhibiting less agglomerations. The percolation zone of AC and DC resistivity of NSPC composite ranges between 1 and 2 wt.%, and the established percolation threshold is at 2 wt.%. XRD analysis showed C-S-H formation consistently increased with curing age, and HR-SEM with EDAX analysis exhibits the dense microstructure and well-distributed NSPC particle at the nanoscale. These experimental outcomes significantly enhanced the reliability and provided a framework for tailoring NSPC particle as SCN for developing electrically conductive composite.

Enhanced emergent electromagnetic inductance in Tb5Sb3 due to highly disordered helimagnetism

In helimagnetic metals, ac current-driven spin motions can generate emergent electric fields acting on conduction electrons, leading to emergent electromagnetic induction (EEMI). Recent experiments reveal the EEMI signal generally shows a strongly current-nonlinear response. In this study, we investigate the EEMI of Tb5Sb3, a short-period helimagnet. Using small angle neutron scattering we show that Tb5Sb3 hosts highly disordered helimagnetism with a distribution of spin-helix periodicity. The current-nonlinear dynamics of the disordered spin helix in Tb5Sb3 indeed shows up as the nonlinear electrical resistivity (real part of ac resistivity), and even more clearly as a nonlinear and huge EEMI (imaginary part of ac resistivity) response. The magnitude of the EEMI reaches as large as several tens of μH for Tb5Sb3 devices on the scale of several tens of μm, originating to noncollinear spin textures possibly even without long-range helimagnetic order.

Quantum spin liquid ground state in the trimer rhodate Ba4NbRh3O12

Frustrated magnets offer a plethora of exotic magnetic ground states, including quantum spin liquids (QSLs), in which enhanced quantum fluctuations prevent a long-range magnetic ordering of the strongly correlated spins down to lowest temperature. Here we have investigated the trimer based mixed valence hexagonal rhodate Ba4NbRh3O12 using a combination of dc and ac magnetization, electrical resistivity, specific heat, and muon spin rotation/relaxation (μSR) measurements. Despite the substantial antiferromagnetic exchange interactions, as evident from the Weiss temperature (θW∼−35 to −45K), among the Rh-local moments, neither long-range magnetic ordering nor spin freezing is observed down to at least 50 mK, in ac-susceptibility, specific heat, and zero-field μSR measurements (down to 0.26 K). We ascribe the absence of any magnetic transition to enhanced quantum fluctuations as a result of geometrical frustration arising out of the edge-sharing equilateral Rh-triangular network in the structure. Our longitudinal-field μSR result evidences persistent spin fluctuations down to 0.26 K, thus stabilizing a dynamic QSL ground state in Ba4NbRh3O12. Furthermore, the magnetic specific heat data at low T reveal a significant T-linear contribution plus a quadratic T dependence, which may indicate the gapless Dirac QSL phenomenology of the spinon excitations with a linear dispersion. Published by the American Physical Society 2024

Investigation of structural, electrical, and magnetic variations of Ni-Zn-Co ferrites by substituting rare earth Ho3+ for high-frequency applications

The investigation of structural, magnetic, and electrical properties of Ni0.6Zn0.3Co0.1HoxFe2−xO4 (NZCHF, 0 ≤ x ≤ 0.2) ferrites, synthesized through the sol–gel autocombustion method, has been undertaken. The refined x-ray diffraction (XRD) analysis was performed for XRD data analysis using Fullprof Suite software and it confirmed a single-phase cubic spinel structure, with the determination of crystallite size, refinement parameters and lattice constants. The bulk density of the samples consistently remained lower than the x-ray density, with densities increasing proportionally to the enhancement of Ho concentration. FTIR analysis corroborated the presence of metal-oxygen bonds within the ferrite possessing a spinel cubic structure. 57Fe Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Ho3+ ions that preferentially occupy the B site. The impedance analyzer and vibrating sample magnetometer (VSM) were utilized to measure the real and imaginary parts of the complex permeability and magnetic properties of the samples, respectively. Complex impedance plots were scrutinized to discern the contributions of grain and grain boundary resistances, providing insights into the electrical behavior of the ferrite samples. Furthermore, the introduction of Ho concentration led to alterations in other key properties of the ferrites, including coercivity (H c ), retentivity (M r ), anisotropy constant (K), and magnetic moment (μ B ).The impact of the rare-earth content on the magnetic features of the prepared NiZnCo ferrite microspheres was investigated by analyzing magnetic-hysteresis (M-H) loops, which showed soft ferrimagnetism. Concurrently, the dielectric constant and dielectric loss tangent of the studied samples exhibited a decrease with the rise in Ho3+ concentration. The expected reduction in tan loss in the prepared samples is attributed to the increase in ac resistivity associated with the higher Ho3+ content.

EXPERIMENTAL STUDY OF THE CHLORIDE-ION PERMEABILITY OF BAMBOO-FIBER-REINFORCED CONCRETE

This study investigated the chloride-ion permeability of C30 concrete by adding bamboo fibers with different treatments (untreated, treated with calcium hydroxide solution and treated with sodium hydroxide solution) and different dosages. Three testing methods, namely the electric-flux method, AC test method and the RCM method, were used to characterize the concrete. Parameters such as electric-flux value, AC resistivity and chloride-ion diffusion coefficient were obtained. Results showed that the surface impurities of the bamboo fibers treated with calcium hydroxide solution were removed and the thermal stability of the bamboo fibers was improved, which can effectively enhance the chloride-ion permeability of concrete. Compared to untreated bamboo fibers, the improvement rate was between 14 % and 17 %. Sodium hydroxide is a strong alkaline solution, which can easily disrupt the structure of bamboo fibers and reduce the resistance of concrete to chloride-ion penetration. The best chloride-ion permeability was achieved when the bamboo fiber content reached 2 %. The electric-flux method, AC test method, and the RCM method were mutually validated with good correlation. It is recommended to choose a suitable and simple method for testing. Bamboo-fiber concrete lays a solid foundation for the future transformation of the civil-engineering industry.

Novel Mn0.5Zn0.5Al0.1MgxLixFe(1.9-x)O4 nanoferrites: synthesis, theoretical cation distribution, and improving their dielectric properties

The effect of Mg2+–Li1+ ions in modifying the structural, electrical, and magnetic characteristics of nanocrystalline Mn–Al–Zn ferrites was examined experimentally and theoretically in the current study. The chemical co-precipitation method was used to create the investigated ferrite samples, which have the chemical formula (Mn0.5Zn0.5 Al0.1Mgx Lix Fe(1.9-x)O4) and concentration range of the substituent (0 ≤ x ≤ 0.2). The cation distribution of the investigated system was assumed and confirmed. Furthermore, the activation energy, AC resistivity, dielectric loss tangent, and dielectric constant were investigated in terms of their compositional dependence. The final results showed that the increasing of Mg2+–Li1+ concentration enhanced the physical and dielectric properties of the prepared samples. The experimental findings show also that as temperature rises, ε′, tan δ, and σ all increase but they all decrease as Mg2+–Li1+ content increases. With increasing Mg2+–Li1+ concentration, the AC resistivity of the prepared samples also continuously increased, resulting in the sample with x = 0.2 having high resistivity, which can be used in specific technical applications such as transformer cores.

Structural, thermal, optical, magnetic and electrical properties of Fe doped Ba0.77Ca0.23TiO3 perovskite

The most known ferroelectric ceramic material is Barium Titanate (BaTiO3), which is frequently used in actuators, capacitors, and memory devices. The ferroelectric properties of Barium Titanate were improved by doping a small amount of other dopants. Choosing a material with high ferroelectric, piezoelectric, dielectric, and magnetic constants, low dielectric loss, and high electrical resistivity is necessary. In order to achieve the purpose, the suggested sample is formed as Ba0.77Ca0.23Ti1-xFexO3, where x is equivalent to 0.0, 0.05, 0.15, and 0.20. We doped iron (Fe), replacing titanium, and the percentage of calcium was fixed. The composition was synthesized by the conventional solid-state reaction (SSR) method. Effects of ferrite contents (x) on the structural, thermal, optical, dielectric, magnetic, and electrical properties were thoroughly investigated. The structural properties and phase identification were studied by powder X-ray diffraction (XRD), confirming the formation of the cubic crystal structure of perovskite samples. While increasing Fe contents (x), the lattice parameter of the samples increases slightly but dramatically decreases for x = 0.20. Differential Scanning Calorimeter (DSC) results that the specific heat capacity is highest at 1100 °C. Fourier-transform infrared spectroscopy (FTIR) analyses confirmed the metal-oxygen corresponding bonds at 370 cm−1 and 530 cm−1 in the perovskite structure. The bandgap (Eg) values decrease from 2.46eV to 1.75eV with Fe added in the sample studied by exploiting ultraviolet–visible spectroscopy (UV–Vis). The magnetization increases with the addition of an applied magnetic field and Fe contents. The dielectric parameters, permeability, impedance, and AC resistivity have been extracted from the measurement of the Impedance Analyzer. As band gap energy decreases, the compositions can be good candidates for memory devices. Low magnetization can make these compositions a good choice for spintronics, memory devices, and catalysis.

Studies of structural, dielectric, conductivity, leakage current mechanism, and efficiency of complex electroceramic

Bismuth ferrites are quite interesting because of their high conductivity and dielectric constant. Recent times now need innovative materials with high mechanical strength, minimal energy loss, and cost effective. The analysis of X-ray diffraction pattern/data and scanning electron micrograph provides the formation of complex bismuth ferrite containing lithium and tungsten of a composition Bi1/2Li1/2Fe1/2W1/2O3, with monoclinic symmetry. The relation between the electrical and dielectric characteristics was examined in the frequency region from 1 kHz to 1 MHz at different temperatures (25–500 °C). The electrical conductivity experiments on the compound containing lithium and tungstate produced some exciting findings. As the frequency increases, the ac resistivity showing decreasing trend with small resistance and large conductivity. With the help of non-overlapping small polaron tunneling (NSPT) and overlapping large polaron tunneling (OLPT) models, temperature-frequency dependent conduction mechanisms have been explained. When electrical characteristics are examined using impedance spectroscopy (non-Debye relaxation), the contributions of grain and grain boundaries effect in the material are observed in the material. The Ohmic and Space Charge Limited Current conduction mechanism (SCLC) were found at low and high electric field (voltage) under forward bias current-voltage situations. The energy storage efficiency of the material is 61.80 %, obtained at room temperature with an applied electric field (−3 to +3 kV/cm) at a frequency of 50 kHz from the hysteresis loop. It implies that the material is promising for pulsed power energy storage capacitors.

Synthesis and characterization of structural, magnetic and electrical properties of Mn substituted Co-Zn ferrite

Spinel – type Zn0.5Co0.5 - xMnxFe2O3 ferrites were synthesized via solid-state reaction method with x values of 0.0, 0.1, 0.2, 0.3, and 0.4. X-ray diffraction was used to identify the crystallographic structure, which revealed the formation of a single-phase cubic spinel structure. The lattice parameter of Co-Zn ferrite samples was measured with a maximum value of 8.76 Å, and the density decreased with increasing concentration. The average grain size decreased with increasing Mn concentration. The Vibrating sample magnetometry (VSM) technique confirmed the soft ferromagnetic character of the entire sample, with a maximum magnetic saturation value of 73.67 emu/g, which was decreased with increasing Mn concentration. The magnetic coercivity (Oe) value led to a slightly hard magnetic phase with increasing Mn concentration, with a maximum value of 6.22. AC resistivity and permeability decreased with increasing frequency but were more activated at lower frequency, which is typical for ferrite behavior. The resistivity and dielectric constant correlated with the value of porosity and bulk density with increasing Mn percentage.

Characterization of Nano-Structured Magnesium-Aluminum Ferrites Synthesized by Citrate-Gel Auto Combustion Method

An effort is made to find the solution to the new challenges of modification advancements in ferrite technologies. The hypothetical variation in the structural, magnetic, and electrical properties of cubic spinel magnesium aluminum ferrites introduced by the substitution of doping elements has been rationalized and proven. The outcome of aluminum substitution on the magnesium ferrites has been examined and investigated. Spinel ferrites having compositions of MgAlxFe2-xO4 (x = 0.1, 0.2, 0.3, 0.4) were prepared by the sol-gel auto-combustion method. The prepared sample’s characterization, such as scanning electron microscopy (SEM), DC electrical resistivity, AC electrical resistivity, and dielectric properties measurements, were tested using the respective instruments. The grain size and crystal size of all samples were measured from the micrographs of SEM and XRD Data. It is found that the average grain size is within the range of 300 nm - 550 nm for all different series that are formed, keeping the samples at 1100 °C sintering temperatures. A two-probe method experiment with a temperature range of 30 °C to 500 °C gives data on DC electrical resistivity. The Curie temperature depends on the sintering temperature, and it increases with increasing doping concentration. Also, doping influences grain size, which decreases with increasing concentration. Analyzing the SEM micrographs, it is found that the average grain size must decrease in tendency with increasing Al content. DC electrical resistivity exhibits excellent semiconducting behavior. Frequency dependence, dielectric constant, and dielectric loss factors were measured, keeping the frequency range of 75 Hz to 130 MHz at room temperature. The result shows that the dielectric constant (e) and dielectric loss tangent (tan™) decrease with the increase in frequency, while the AC resistivity and Q-factor increase. Comparing the electrical properties of four compositions, it can be suggested that the mixed ferrite, sample-4 (x = 0.3), shows the highest Q-factor of all at 1100 °C.

Preparation of multifunctional flame-retardant coating of cotton fabrics for electrical Insulating applications

Cotton fabric (CF) was coated with a new multifunctional flame-retardant system consisting of melamine phosphate (MP) and nickel (II) dimethylglyoxime (NDMG). The new coating was applied to enhance the flame retardancy, antibacterial activity, thermal stability, color strength, UV protection, and electrical properties of CF. The weight percentages of NDMG and MP that led to the maximum improvement in CF properties were identified. According to vertical and horizontal flammability tests, coating the fabric with 29%MP/1%NDMG prevented flame propagation in the samples. Moreover, it increased the limiting oxygen index (LOI) of CF from 17.9% to 36.9%. Thermogravimetric analysis (TGA) data presented that the MP/NDMG coating enhanced the char residue at 750°C. Antimicrobial investigations indicated that the coating 29%MP/1%NDMG reduced the growth of S. aureus and E. coli bacteria. UV shielding and color strength (K/S) results revealed that coated fabrics had excellent UV protection (UPF > 175) and enhanced K/S values. The tensile strength of CF was slightly decreased after the coating process. The dielectric constant (ε`), the dielectric loss (ε``), and AC electrical resistivity ([Formula: see text]) with frequency (10-106 Hz) were also investigated. The electrical resistivity increased significantly after adding MP and NDMG to the CFs. The coated sample (23%MP/7%NDMG) showed the best dielectric properties, with a low dielectric constant of 2.6 and [Formula: see text] of 1.40E+10 Ω.cm at 1000 Hz.

High resistivity free-standing crosslinked graphene oxide substrates: hopping conduction mechanism and application to recyclable electronics

Graphene oxide (GO) is an oxidized derivative of graphene that can be formed into free-standing wafers by aqueous processing methods. We propose GO as a potential alternative printed electronic substrate material to mitigate the waste electronic and electrical equipment problem. By dissolving these substrates in water, GO permits the mechanical separation and recovery of discrete components from defunct circuits, thus closing the life cycle of printed circuits. In this work we measure the anisotropic, frequency dependent resistivity of free-standing GO wafers under DC and AC (f = 0.1 Hz–500 kHz) excitation and in varying relative humidity (RH) conditions. Unmodified GO and GO crosslinked with calcium ions, borate ions, and glutaraldehyde were characterized. AC resistivity measurements reveal charge transport in free-standing GO occurs by several distinct hopping conduction mechanisms that are sensitive to the crosslinking formulation. GO crosslinked with calcium ions exhibits the highest DC resistivity, 4.6 × 105 Ωm and 2.6 × 104 Ωm, for out-of-plane and in-plane directions, respectively, at 17% RH. Both AC and DC resistivities decrease with increasing RH. We demonstrate that GO wafers can be used as dielectric substrates in the construction of simple electronic circuits with discrete electronic components. Finally, we present a proof-of-concept for electrical trace and component recovery via disassembly of GO wafers in water.

Synthesis of Sr-doped Ni0.5Zn0.5SrxFe2-xO4 and the study of its structural, mechanical, magnetic, and electrical properties for high-frequency applications

The solid-state reaction method has been used to mold the spinel Ni–Zn ferrites with doped strontium (Sr) [Ni0.5Zn0.5SrxFe2-xO4; x = 0.00, 0.01, 0.03, 0.05, and 0.10]. The powder X-ray diffraction approach was driven to investigate the crystal lattice of the studied samples. By using a variety of methods, including the Debye-Scherrer (D-S) formula, the Williamson-Hall (W–H), the Halder-Wagner (H–W), and the size-strain plot (SSP), where broadening of the XRD peaks are used, we have calculated the crystallographic features of Ni–Zn ferrites to ascertain the crystallite size and lattice strain. With doped Sr contents in samples, the lattice constants of the studied ferrites were decreased. Scanning electron microscopy (SEM) was used to analyze the sample's surface. Using the Image J software, the samples' grain size was calculated. We also performed the FTIR calculation, which confirmed that the ferrites we studied were spinel ferrites. The stiffness constants and elastic moduli were enumerated using the FTIR data to evaluate the mechanical behavior of the studied samples. Important thermal parameters such as Debye temperature (ΘD) and melting temperature (Tm) were also calculated. The magnetic behavior characterizing parameters have been analyzed via a vibrating sample magnetometer (VSM). Our studied samples are soft magnetic materials. We found the magnetic and electric losses to be negligible. Over a wide frequency extent, from 102 to 106 Hz at ambient temperature, an impedance analyzer was utilized to examine the samples' dielectric properties and AC resistivity. In the high-frequency region, the dielectric constant is frequency independent and the values of the dielectric constant are decreased with doped materials. Resistivity is increased with Sr-doped materials.

Study of temperature and frequency dependant dielectric, impedance, AC resistivity, modulus spectroscopy and electromechanical coupling properties of [BaNd0.1Ti0.8Nb0.1O3](1-x)[Na0.5Bi0.5TiO3]x relaxor ferroelectric ceramics

[BaNd0.1Ti0.8Nb0.1O3](1-x)[Na0.5Bi0.5TiO3]x ceramics with x = 0.25, 0.40, 0.60, 0.65 & 0.70 were prepared through solid-state sintering route. In the present study, temperature and frequency dependant dielectric, Impedance, AC resistivity, modulus spectroscopy and electromechanical coupling properties carried out. These materials showed modulus resonance and anti-resonance i.e. electromechanical coupling (M″ vs. frequency). From these modulus resonance and anti-resonance studies piezoelectric charge constant (d33) was obtained. The values of the piezoelectric charge constant (d33) are 3.34 nm V−1, 6.26 nm V−1, 11.58 nm V−1, 14.10 nm V−1 & 10.70 nm V−1 for x = 0.25, 0.40, 0.60, 0.65 & 0.70, respectively. In the present study, the modulus electromechanical was studied in jig with spring which applies constant stress on the ceramic sample. The higher value of electromechanical coupling conversion in the present study may be attributed to this constant applied stress, higher temperature and polarized oxygen vacancies at the crystal lattice at these elevated temperatures (773 K & 873 K).

The role of Zn and Ru substitution on the structural, magnetic and dielectric properties of ferrite cuprospinels

A comprehensive study on the structural, magnetic and dielectric behavior of ferrite cuprospinels with site specific substitution of non-magnetic Zn and weakly magnetic Ru ions has been presented. Such substitution leads to two classes of stable crystal symmetries, (i) tetragonal (I41/amd): CuFe1.95Ru0.05O4 and Cu0.95Zn0.05Fe1.95Ru0.05O4 and (ii) cubic (Fd-3m):Cu0.60Zn0.40Fe1.95Ru0.05O4 and Cu0.05Zn0.95Fe1.95Ru0.05O4 bulk polycrystals. The former set of compounds undergo significant Jahn-Teller (JT) distortion due to high Cu content and such distortion gets lifted with the substitution of non-magnetic Zn ions. Ferrimagnetic (FiM) behavior is predominant in all these compounds except the highest Zn (95 at.%) content cubic system with diluted substitution of Ru (2.5 at.%) which exhibits antiferromagnetic ordering below the Néel temperature (T N ∼ 10.9 K). We employed Néel’s expression for FiM systems applicable for the two sublattice model to extract the dominant exchange interactions (J AA , J AB and J BB ) between the A-site and B-site cations. Subsequently the high temperature (300 K T 900 K) inverse paramagnetic susceptibility data has been fitted to the above expression which yields dominant ∼ 391 K with very high asymptotic Curie temperature for the tetragonally distorted dilute Zn substituted cuprospinel, while the Zn-rich cubic system exhibits ∼ 300 K. On the other hand, the tetragonally distorted spinel devoid of Zn exhibits dominant ∼ 229 K with negligible and moderate (65 K) signifying that the JT active ions cause the onset of magnetic frustration and enhanced ordering temperatures. All the investigated systems exhibit significant magneto-crystalline anisotropy with a maximum anisotropy field H K ∼ 6 kOe and maximum anisotropy constant (K 1 ∼ 10.88×105 erg cm−3). The broadband dielectric spectroscopy studies reveal significant enhancement of mid-frequency dielectric constant ε R (f, T) with plateau-like feature over a wide temperature and frequency window, together with low-loss as a result of the incorporation of Ru ions into the tetragonally distorted spinel lattice. The ac resistivity ρ(f, T) studies reveal that the mode of conduction follows Mott’s variable-range hopping (VRH) model with a linear logarithmic variation of ρ ac versus T −0.25. The temperature dependence of the VRH activation energy of charge carriers follows a linear behavior which indicates the presence of localized polaron in all the investigated systems.

Structural, morphological and frequency dependent dielectric properties of [formula omitted][formula omitted]) nanoparticles prepared by sol-gel method

In this work, the spinel ferrite NixZn0.6−xMn0.4Fe2O4(x=0.0,0.1,0.2,0.3,0.4) nanoparticles (NPs) have been synthesized via the sol-gel method. It is observed that the presence of Ni2+ ions cause an appreciable change in the different properties of the Ni substituted Zn0.6−xMn0.4Fe2O4 NPs. The Fourier transform infrared (FTIR) spectroscopy analysis confirms the formation of the NixZn0.6−xMn0.4Fe2O4 spinel structure. Rietveld's refinement of X-Ray Diffraction (XRD) patterns confirms the single-phase cubic spinel structure belonging to the Fd3m space group. The estimated lattice constant is found to decrease with increasing Ni contents except for x=0.1 and the average crystallite size varies from 6.7nmto100nm due to the reduction of grain growth upon Ni2+ occupation in the octahedral site. Frequency-dependent dielectric constant, dielectric loss, AC resistivity, and conductivity of the compositions have also been examined at room temperature. The ac resistivity exponentially decreases with the increase of frequency due to the effect of multilayer capacitance. Conversely, the ac conductivity is observed to increase exponentially with the frequency due to increased hopping between metallic cations Fe2+ and Fe3+. The electrical charge conduction behavior and contribution of grain and grain boundary resistance have been explained using Nyquist/Cole-Cole plot. Hence, the Ni doped Zn0.6−xMn0.4Fe2O4 NPs excellent dielectric behavior can be used for various potential applications including the fabrication of the nano-electronic device and multi-layers chip inductors applications.

Percolative transport and metamagnetic transition in phase separated La0.55Ca0.45Mn1-xAlxO3-δ

The Al3+ doping effects on the ferromagnetic metallic state of La0.55Ca0.45MnO3 have been studied by preparing the La0.55Ca0.45Mn1-xAlxO3-δ (x = 0, 0.05, 0.1, 0.15) ceramics. Various measurements such as ac susceptibility, relaxation, magnetization and resistivity were performed to study the magnetic and magnetotransport properties. The magnetic disorder produced by the Al3+ dopants and the oxygen vacancies suppress the long range ferromagnetic ordering and induce a short range charge ordered antiferromagnetic clusters, leading to a phase separated behavior in the Al3+-doped samples. A Griffith-like behavior is observed due to the occurrence of short range ferromagnetic clusters in the paramagnetic phase. The 15% Al3+ doping sample exhibits a spin-glass state. The 10% Al3+ doping system is blocked in a metastable state upon cooling at zero field, and a sharp metamagnetic transition is induced by applying a high magnetic field, in which the antiferromagnetic phase is transformed into ferromagnetic phase and the ferromagnetic clusters grow in size. The ferromagnetic domains grows rapidly when applying a high magnetic field. Once the conducting ferromagnetic domains are interconnected throughout the sample, a percolative insulating-to-metallic state transition would occur, accompanied by a sharp drop in resistivity.

Role of Mn2+ ion in the optimization of the structural and dielectric properties of Co–Zn ferrite

Mn-substituted Co–Zn ferrite nanomaterials with the general form Co0.8−x Mnx Zn0.2 Fe2O4 (x = 0.0, 0.1, 0.2, and 0.3) were prepared using the coprecipitation method. Based on X-ray diffraction, it can be confirmed that all samples have a single-phase cubic structure with an average crystallite size ranging from 23.46 to 32.66 nm. In addition, the lattice parameter increased from 8.32 to 8.37 Å. In this study, the theoretical density was calculated, and the Fourier-transform infrared spectra of the prepared samples were investigated. Further, the cation distribution of the system was estimated. The proposed cation distribution was confirmed by calculating the theoretical lattice parameter and comparing it with the experimental lattice parameter. We conducted transmission electron microscopy to confirm the obtained particle size. At room temperature, the electrical measurements of the prepared samples were performed using the LCR circuit as a function of frequency up to 5 MHz. In this study, we obtained enhanced dielectric properties by substituting Mn ions in the Co–Zn ferrite. As the Mn concentration increases, the AC resistivity of the samples increases. Consequently, the dielectric loss decreases, and its minimum value can be observed at x = 0.2, making the Co–Mn–Zn ferrite suitable for applications in the microwave frequency range. The results show that all dielectric properties exhibit a normal behavior with frequency. We obtained an improvement in the dielectric properties of the prepared samples, making them suitable for use in high-frequency applications due to the substitution by Mn ions.