Enhanced Saturation Magnetization Research Articles

Pr-modified microstructure enhances coercivity in Sm2Co17-type magnets

Optimizing components of the cellular structure is a strategy to enhance the magnetic performance of Sm2Co17-type magnets. In this study, Pr is used to modify the cellular structure in Sm2Co17-type magnets, achieving synergistic optimization of coercivity from 32.12 kOe to 34.71 kOe and remanence from 11.23 kGs to 11.36 kGs. Analyses reveal that the increased remanence is attributed to the enhanced saturation magnetization and better grain alignment in the Pr-5 magnet. The incomplete cellular structures and Cu-lean region near grain boundaries are ameliorated in the Pr-5 magnets. Meanwhile, the Pr-modified and Cu-enriched cellular boundary phase, which has a lower magnetocrystalline anisotropy field, enhances the pinning strength of the domain-wall and contributes to the increase in coercivity. The substitution of Pr for Sm has a lower substitution energy in SmCo5 than in Sm2Co17, leading to the slight enrichment of Pr in the 1:5H phase. However, excessive Pr leads to increased amounts of oxides and deteriorates magnetic properties. This work provides valuable insights into developing high-performance Sm2Co17-type magnets by optimizing the microstructure and microchemical components.

Rare earth samarium substituted barium-calcium hexaferrites: Insight into structure, dielectric and magnetic aspects

This study presents the synthesis of samarium-substituted Ba-Ca hexaferrites (Ba0.5Ca0.5Fe12-xSmxO19) utilizing the sol–gel method. X-ray diffraction (XRD) analysis is performed to evaluate the structure of fabricated materials. The lattice shows an expansion up to a doping concentration of x = 0.12, and minor contraction at x = 0.16. Both X-ray density and bulk density exhibit an upward trend with increasing doping levels, while porosity reduces and dislocation density shows an increase. Scanning electron microscopy (SEM) confirms the homogeneity and uniformity of the doped samples. The dielectric properties displays the interaction of the materials with an external electric field, revealing that the dielectric constant (ε′), dielectric loss (ε″), and dissipation factor progressively increases with samarium concentration. Magnetic characterizations demonstrate a significant enhancement in saturation magnetization and coercivity, attaining peak values of 33.19 emu/g and 1.805 kOe, respectively. Moreover, the anisotropy field (Ha) and anisotropy constant (K) shows an increase with higher doping concentrations confirming the prepared material as an alternative for electric and magnetic industry applications.

Characterization of Co-doped Ni-Mn spinel nanoferrites: A Multi-faceted evaluation of structural, optical, elastic, and magnetic properties

This study presents the synthesis and comprehensive evaluation of nanocrystalline CoxNi0.5-xMn0.5Fe2O4 (0.0 ≤ x ≤ 0.5) ferrites. Utilizing a variety of analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM), we characterized the structural, optical, elastic, and magnetic properties of the synthesized nanoparticles. Our findings reveal that increasing Co content leads to a systematic increase in lattice constant from 8.33 Å to 8.39 Å and influences the crystallite size, which ranges between 10 and 15 nm as determined by XRD. Notably, the band gaps of these nanoparticles span from 2.8 to 3.6 eV, varying with Co concentration. Magnetic measurements indicate a transition from superparamagnetic-like behavior at x = 0 to enhanced saturation magnetization, remanence, and coercivity with higher Co content. The novelty of this research lies in the detailed correlation between Co substitution and the resultant changes in multiple physical properties of NiMn nanoferrite, offering potential applications in various technological fields such as magnetic storage, sensors, and biomedical applications.

High permeability and low loss easy-plane ferrites with multi-ions doped for miniaturized 5G antennas

Ferrites are the desirable candidates for antenna substrates due to their high permeability and low magnetic loss. However, such excellent magnetic properties cannot be maintained in the GHz band due to the Snoek limit. Here, we report a BaCo1.8Zn0.2Fe16O27 (CoZnW) ferrite prepared by doping multiple ions at the lattice (Zn ions) and grain boundaries (Bi/Ca/Si/V ions) of conventional BaCo2Fe16O27 (Co2W) ferrites, achieving a high permeability of 3.3, low magnetic loss tangent of 0.05, and a high figure of merit (FOM=μ′Qf = 66) at 1 GHz, which is much better compared to the previous reports. Moreover, the dimensions of the antenna deploying the multi-ions doped CoZnW are only 52 % of those deploying conventional commercial materials (Fr4) because of its high permeability and low loss. Such a high permeability is attributed to the enhanced saturation magnetization and the reduced anisotropic field achieved by Zn ions modulation. The low magnetic loss is attributed to the reduced damping of domain wall motion and the refined grain size achieved by Bi/Ca/Si/V ions modulation. Our work not only provides a promising candidate for 5G antennas but also uncovers a physical mechanism for the modulation of magnetic properties of ferrites.

Elucidation of structural, electromagnetic, and optical properties of Cu–Mg ferrite nanoparticles

Copper doped magnesium ferrite, Mg1-xCuxFe2O4(x = 0.0–1.0) nanomaterials were synthesized via. sol-gel method sintered at 600 °C for 2 h. The synthesized materials were characterized using modern sophisticated techniques viz. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy, Energy dispersive x-ray spectroscopy (EDS), Vibrating sample magnetometer, UV–visible diffuse reflectance spectra and Impedance analyzer. XRD analysis revealed that all the samples were single phase cubic spinel structure with Fd3m space group and investigated the change in structural parameters with copper concentration. The average crystallite size in the range of 11–23 nm and lattice parameters decrease with increasing Cu doping, due to the cationic distribution and ionic radius. The SEM images show the agglomeration of the particles with spherical like shape and elemental percentage were obtained from EDX. The saturation magnetization showed an increasing trend with increasing Cu concentration at a certain level and then decreases due to the rearrangement of cations at tetrahedral and octahedral sites. The Coercivity, Retentivity and magnetic crystalline anisotropy increase with changing dopant concentration. The magnetic measurements showed enhanced saturation magnetization at certain level (28.96emu/gm) and increase in coercivity up to 1102 Oe with changing dopant concentration. The estimated band gap energy is found to increase with Cu content. The dielectric constant, dielectric loss and impedance show normal behavior of ferrite. The frequency dependent dielectric constant decrease and tan delta shows a relaxation behavior at low frequencies. The synthesized nano Mg–Cu nanoparticles will be applied as humidity sensor, gas sensor, microwave devices and photocatalyst.

Hydrogen-annealing modulated magnetocaloric effect and critical behavior of Weyl semimetallic Co3Sn2S2

Modulating the electron interaction and magnetic domains is an essential strategy to evoke novel physical properties, both for fundamental research and for related magnetic applications. The emerging annealing process attracted attention due to its capability of tuning the magnetic performance, but it has been rarely studied. Herein, we conducted hydrogen annealing on the Weyl semimetallic Co3Sn2S2 and investigated the magnetic interaction, critical behavior, and magnetocaloric effect (MCE). Hydrogen-annealed Co3Sn2S2 (HA-Co3Sn2S2) exhibits a distinct anisotropy-dependent magnetic behavior, where a typical second-order transition with an easy magnetization process is observed under H//c. However, a frustrated magnetic state composed of ferromagnetic (FM), antiferromagnetic (AFM), and/or spin glass phases is observed when H//ab. Critical analyses illustrate that the ground state of HA-Co3Sn2S2 lies between the 3D-Ising model and the Mean-filed model, indicating the presence of both long-range and short-range magnetic interactions in the system. Additionally, we found that HA-Co3Sn2S2 exhibits an enhanced saturation magnetization (Ms) and magnetic refrigeration capacity, both showing anisotropic dependence, compared to the pristine Co3Sn2S2. Our work develops hydrogen annealing to modulate electron coupling and magnetic domains, paving the way for further studies of anisotropic magnetic behavior and applications in magnetic refrigeration.

Exploring the supercapacitive potential of Sm3+ doped CoFe2O4 nanoparticles: Enhanced magnetic and dielectric properties

This study investigates the impact of Sm3+ substitution on the structural, electrical, magnetic, and electrochemical properties of CoFe2O4 nanoparticles prepared via a combined solid-state reaction and mechanical milling approach. Rietveld refinement analysis confirms the presence of single-phase cubic spinel structures within the Fd3m space group for both CoFe2O4 (CF) and Co0.95Sm0.05Fe2O4 (SmCF). Field emission scanning electron microscopy and energy dispersive spectroscopy are employed to validate the microstructure and elemental composition. Tauc plot analysis reveals a decrease in the band gap from 2.24 eV for CF to 2.07 eV for SmCF. Hysteresis loop measurements demonstrate an enhancement in saturation magnetization, remanent magnetization, and magnetic moment for SmCF, indicating improved magnetic properties. Furthermore, a substantial increase in magneto-crystalline anisotropy is observed with Sm³⁺ doping. Frequency-dependent dielectric properties are investigated using Havriliak–Negami fitting, confirming the presence of Cole-Cole dispersion. A direct correlation between the dielectric constant and temperature is identified, suggesting higher temperatures lead to elevated values. Notably, the incorporation of Sm³⁺ results in a significant enhancement in specific capacitance, positioning SmCF as a promising candidate for energy storage applications, particularly in supercapacitors.

Enhanced Ferromagnetism in Atomically Thin Oxides Achieved by Interfacial Reconstruction

AbstractDiscoveries of ferromagnetic materials with ultrathin thickness are of great importance for both fundamental science and technological applications. Transition metal oxides (TMOs) provide promising candidates in the context of next‐generation spintronics, despite the severe decay of ferromagnetism as the thickness reduces to the nanometer regime. Here, an efficient strategy to eliminate the magnetic dead layer in atomically thin oxides is presented, by using the epitaxial interface of 3d and 5d oxide monolayers that reconciles both strong exchange interaction and large uniaxial magnetic anisotropy. Combining multiple experimental methods, a ferromagnetic transition in an ultrathin oxide heterostructure comprised of only one La0.2Sr0.8MnO3 monolayer sandwiched by SrIrO3 monolayer (total thickness of three unit‐cells) is unambiguously demonstrated. Remarkably, a largely enhanced saturation magnetization (2 µB Mn−1) and Curie temperature (80 K) are observed for the single manganite monolayer, as compared to previously reported ferromagnetic monolayer oxides. The results demonstrate a general strategy for creating robust ferromagnetism in ultrathin TMOs, potentially enabling novel oxide spin‐orbitronic devices.

Magneto-chemical properties of Ti-doped Co3O4 nanosheets for photocatalytic activity applications

The 2D nanosheets of Ti-doped Co3O4 were prepared by hydrothermal technique to understand their dimensional effectiveness for the application of photocatalytic dye degradation. These nanosheets were well characterized for crystal structure, morphology, and composition. The energy band gap for 3% Ti-doped Co3O4 nanosheets was reduced. The 3% Ti-doped Co3O4 shows a reduction in crystallite size, band gap, and an enhancement in saturation magnetization, photosensitivity, and defects. The photocatalytic activity of Ti-doped Co3O4 nanosheets is higher than Co3O4. The small amount of Ti improves the structural, optical, and magnetic properties and photocatalytic action of the as-prepared samples. After successful doping of Ti into Co3O4 lattice the saturated magnetization of Co3O4 was enhanced. The sample 3% Ti-doped Co3O4 nanosheet shows high photosensitivity. The effect of photosensitivity on the photocatalytic activity was scrutinized by I-V characteristics. After being exposed to sunlight 3% Ti-doped Co3O4 nanosheet showed an electrical resistance ∼ 129 kΩ. Also, the effect of oxidizing reagents (H2O2) and reducing reagents (scavengers) was studied in detail. The photocatalytic efficiency enhances up to 97.29% under sunlight irradiation within 20 min only. The effect of magnetism on enhancement of efficiency for MB dye degradation was discussed in detail. The charge transfer, reducing charge carrier recombination, and increasing the utilization of light energy in catalytic processes were presented in this report at length.

Impact of the Sc3+/In3+ co-substitution on the structural, magnetic, and microwave characteristics of Co0.5Ni0.5Fe2O4 nanospinel ferrites

In this article, In3+ and Sc3+ ions dual-substituted NiCo nanospinel ferrites (ScIn→CoNiFe2O4 NSFs) have been synthesized through citrate-gel auto combustion method to investigate the effect of In3+ and Sc3+ ions on magnetic, and microwave characteristics. The following techniques TEM, SEM, EDX, and XRD were applied to characterize surface morphology, chemical composition, phase identification, and crystallinity of products, respectively. The XRD verified a phase formation of spinel structure with a minor amount of Sc2O3 was observed for products having x ≥ 0.04. The average crystal size (DXRD) of the products was estimated within the 33–68 nm range using the Scherrer equation. SEM and HR-TEM analyses exhibited accumulating sphere-shaped particles. By fitting the room-temperature spectra obtained from Mössbauer spectroscopy (Moss), Hyperfine interactions were determined. The cation distribution shows that there is a migration of In3+ ions in the lattice in an A→B direction with increasing concentrations while the B site is preferred by the larger Sc+3. M−H plots for 300 and 10 K illustrated all products carried out with a ferrimagnetic character. An enhancement in saturation magnetization (Ms) was remarked with Sc–In doping ratio up to 0.04 and thereafter a drop as the Sc–In concentration increased. The tendency in Ms values might be described by correlating it to the cation distribution amongst Oh and Td (octahedral and tetrahedral, respectively) sublattices. Temperature-dependent magnetization measurements were also investigated, which further confirmed the maintenance of the ferrimagnetic character throughout the temperature range 10–300 K. The peculiarities of the microwave properties have been analyzed by the measured S-parameters in the range of 6–18 GHz. It was assumed that the energy losses due to reflection are a combination of electrical and magnetic losses due to polarization processes and magnetization reversal processes in the region of inter-resonant processes. The average value of the reflection coefficient is −14.48 … −14.24 dB. A significant attenuation of the reflected wave energy opens up broad prospects for practical applications as coatings for providing electromagnetic compatibility.

The effect of interfacial charge-induced multiferroic properties of Bi0.993La0.007FeO3/BaTiO3 bilayer thin films: Performance modulation and energy storage applications

Multifunctional and multiferroic materials assure a tantalizing perspective of applications in next-generation microelectronics, memory, energy harvesting, and energy storage technologies. The current study aims to deposit a bilayer thin film of BLFO/BTO with varying top layer (BLFO) thickness on n-type Si and Pt/Ti/SiO2/Si (Pt-Si) substrate by the PLD technique. Bilayer films with dense and packed microstructures show evidence of both tetragonal (T) and rhombohedral (R) symmetry. The bilayer films exhibit remarkably enhanced saturation magnetization of 35.9 emu/cm3 and improved maximum polarization of 34 μC/cm2 at RT compared to single-layer films. Moreover, the higher top layer thickness (BTO/BLFO3) hetero-structures achieved a high recoverable energy storage density of 11.65 J/cm3 with an energy efficiency of 85 % simultaneously. These films display excellent energy storage performance and produce a maximum power density of 0.9 MW/cm3 at 100 Hz. Further, the leakage current density of BLFO/BTO3 film is found ∼102 times lower than the monolayer BTO thin film suggesting the lower oxygen vacancies, defects, and impurities in the bilayer stacked films with higher top layer thickness. The drop in leakage current density, slim hysteresis loop, and enhancement in large saturation polarization for BTO/BLFO3 highlight the improved result demonstrating the interface effect and coupling between ferroelectric and magnetic properties. Hence, the acquired ferroelectric and magnetic properties are promising for spintronic devices and energy storage capacitor applications.

Structural, vibrational and magnetic properties of heat treated CuFe2O4 nanoparticles prepared by two different synthesis routes

The present study employed co-precipitation and high-energy ball milling techniques to synthesize nanoparticles of copper ferrite. Subsequently, the powders underwent air annealing at three distinct temperatures, namely 600 °C, 800 °C, and 1000 °C, for a duration of 3 h. The structural and magnetic properties of the generated compositions were assessed and examined by a range of techniques, including as X-ray diffraction (XRD), infrared (IR) spectroscopy, and vibrating sample magnetometer (VSM). Based on X-ray diffraction examinations, it has been observed that the co-precipitation process results in the production of copper ferrite nanoparticles of smaller size compared to those obtained using the milling procedure. The infrared absorption spectra demonstrated that the enhancement of the annealing temperature resulted in an augmentation of the structural integrity of milled copper ferrite. The results of magnetic investigations conducted at ambient temperature indicate that increasing the annealing temperature resulted in an enhancement of saturation magnetization. The copper ferrite material, which was synthesized using co-precipitation and subsequently subjected to annealing at a temperature of 1000 °C, had the most minimal coercivity value of 138 G and remanence value of 5.26 emu/g. In the context of high-density data storage devices, there is a strong preference for lower coercivity and remanence characteristics. It has been observed that the enhancement of structural and magnetic characteristics requires annealing at elevated temperatures.

Optimization of growth conditions to obtain highly anisotropic FeCo nanowires prepared through magnetic-field-assisted chemical route

In this study, we synthesized one-dimensional α-FeCo nanowires using the magnetic-field-assisted hydrazine reduction method. The amount of hydrazine, NaOH, synthesis temperature and strength of the magnetic field were optimized to obtain high aspect ratio nanowires with good quality. Two samples, obtained at 90 °C (S12) and 60 °C (S34) with improved morphologies and aspect ratios, while keeping the other optimized conditions (Hydrazine - 1 mL; NaOH - 1.5 g and strength of the magnetic field - 4000 Gauss (G)) same, were characterized using various techniques viz. X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), X-ray photoemission spectroscopy (XPS) and dc-magnetization to investigate structural, electronic structural and magnetic properties. Both the samples revealed single-phase α-FeCo formation with body centered cubic (BCC) geometry with space group: Im-3m indicating decrease in the lattice parameter and crystallite dimensions at 60 °C (S34). The influence of synthesis temperature was notably observed on the magnetic properties as well. The saturation magnetization was found to be enhanced from 233 emu/g for S12 to 247 emu/g for S34 along with the enhancement in coercivity. The effective magnetic anisotropy also enhanced to be 2.3× 106 erg/cm3 in S34. In brief, the improvement in aspect ratio and morphology of the wires resulted in the enhancement of saturation magnetization and effective magnetic anisotropy. The enhanced value of magnetocrystalline anisotropy and shape magnetic anisotropy is attributable to the external magnetic field applied during growth and curling of spins due to the reduced diameter of the wires.

Simultaneous existence of magnetic and ferroelectric orders in bi-phase composites for multiferroic applications

Multiferroic materials has brought evolutionary impact in multifunctional devices that are exclusively based on magnetoelectric coupling. In this work, a bi-phasic composite series of the form; (1–x)[Bi0.8La0.2FeO3] + x[Zn0.5Co0.5Fe2O4] was prepared using sol–gel auto–combustion. The X-ray diffraction analysis confirmed the rhombohedrally distorted cubic structure of BiFeO3 and normal spinel cubic structure of Zn0.5Co0.5Fe2O4 having R3c and Fd-3 m space group symmetry, respectively. A reduction in average crystallite size was observed by gradually enhancing the substituent spinel contents (x). Energy dispersive X-ray confirmed the presence of all the constituent elements in accordance with stoichiometrically calculated values. Mostly the particles having spherical shapes were observed via micro-graphical analysis. At x = 0.2, the composite sample showed the highest value of recoverable energy density as 7.2 × 10-2 mJ/cm3 with the highest value of % efficiency ∼ 88.83 %. A clear enhancement in saturation magnetization was observed from 0.16 to 19.87 emu/g. The remanent magnetization also increased from 0.018 to 6.363 emu/g by enhancing the spinel phase contents. Furthermore, coercivity also increased significantly from 672.98 Oe to 841.89 Oe in the composite samples. The highest squareness ratio Mr:Ms was observed at x = 0.3. These distinctive properties of the nanocomposites lead toward potential applications in multiferroic and spintronic devices.

Realization of High Magnetization in Artificially Designed Ni/NiO Layers through Exchange Coupling.

High-magnetization materials play crucial roles in various applications. However, the past few decades have witnessed a stagnation in the discovery of new materials with high magnetization. In this work, Ni/NiO nanocomposites are fabricated by depositing Ni and NiO thin layers alternately, followed by annealing at specific temperatures. Both the as-deposited samples and those annealed at 373 K exhibit low magnetization. However, the samples annealed at 473 K exhibit a significantly enhanced saturation magnetization exceeding 607 emu cm-3 at room temperature, surpassing that of pure Ni (480 emu cm-3). Material characterizations indicate that the composite comprises NiO nanoclusters of size 1-2nm embedded in the Ni matrix. This nanoclustered NiO is primarily responsible for the high magnetization, as confirmed by density functional theory calculations. The calculations also indicate that the NiO clusters are ferromagnetically coupled with Ni, resulting in enhanced magnetization. This work demonstrates a new route toward developing artificial high-magnetization materials using the high magnetic moments of nanoclustered antiferromagnetic materials.

Multiferroic properties of BiFeO3 thin films with Ce substitution

In this study, we investigated the crystalline structure, ferroelectricity, leakage current density, magnetic, and nanomechanical properties of BiFeO3 (BFO) films with Ce substitution. Bi1-xCexFeO3 (BCFO) films with x = 0.00, 0.03, 0.06, 0.09, and 0.15 were deposited on glass substrates by using pulsed laser deposition. The experimental results showed that the BCFO films mainly composed the perovskite phase. The structure changed from rhombohedral when x = 0.00 to pseudo-cubic when x = 0.03, and pseudo-cubic phase coexisted with an additional Bi2Fe4O9 phase when x = 0.06–0.09. The BCFO films exhibited improved ferroelectricity and desirable magnetic characteristics. The remanent polarization (2Pr) increased significantly with the Ce concentration, reaching 189.3 μC/cm2 and 100.0 μC/cm2 when x = 0.03 and x = 0.06, respectively, but decreasing at higher Ce contents. The BCFO film with x = 0.03 had a remarkable 2Pr value of 189 μC/cm2 after 108 cycles due to the high (110) texture, fine microstructure, and flat interface resulting in strong anti-fatigue properties. The leakage mechanisms in the BCFO films were also examined. The films exhibited enhanced saturation magnetization (Ms) values ranging from 3.8 to 10.0 emu/cm3, which were attributed to suppression of the spiral spin configuration and the larger magnetic moment associated with the Ce3+ ion. The nanomechanical characteristics of the BCFO films, such as hardness, were significantly influenced by the grain size and phase composition. These findings provide valuable insights into enhancement of the multiferroic properties of BFO polycrystalline films through Ce substitution for use in various applications.

Enhanced saturation magnetization in La3+ doped NiCo ferrites prepared by sol–gel auto-combustion method

Lanthanum doped nickel–cobalt nano ferrites with chemical formula Ni0.5Co0.5LaxFe2–xO4 (x = 0.05, 0.10, 0.15 and 0.20) were prepared using a simple sol–gel auto combustion method. The basic structural properties were determined by X-ray diffraction method and the formation of single phased spinel ferrite was confirmed. The crystalline size decreased from 25 to 11 nm and lattice parameter a increases with increase of La doping. The surface morphology of these ferrites was observed by field-emission scanning electron microscopy (FESEM) and agglomerated irregular grains are observed with increase of the rare earth element La doping. Energy-dispersive X-ray spectroscopy (EDX) result confirms the presence of the required elements. The Fourier transform infrared spectroscopy (FTIR) spectrum indicates the formation of the spinel ferrite structure with M−O bonds. Optical direct band measurements from ultraviolet–visible spectroscopy (UV-Vis) spectroscopy indicate that the direct band gap decreases from 1.39 to 1.19 eV for x = 0.05 to x = 0.15, then increases to 1.28 eV for x = 0.20. The room temperature magnetic properties of these ferrites were studied by a vibrating sample magnetometer (VSM). The enhanced saturation magnetization of 49.73 emu/g is observed for x = 0.10 and then saturation magnetizations are gradually decreased for x = 0.15 and x = 0.20. Interestingly the remanent magnetization and coercivity also follow the same trend.

Influence of Fe Doping on the Electrochemical Performance of a ZnO-Nanostructure-Based Electrode for Supercapacitors.

ZnO is a potential candidate for providing an economic and environmentally friendly substitute for energy storage materials. Therefore, in this work, Fe-doped ZnO nanostructures prepared using the microwave irradiation procedure were investigated for structural, morphological, magnetic, electronic structural, specific surface area and electrochemical properties to be used as electrodes for supercapacitors. The X-ray diffraction, high-resolution transmission electron microscopy images, and selective-area electron diffraction pattern indicated that the nanocrystalline structures of Fe-doped ZnO were found to possess a hexagonal wurtzite structure. The effect of Fe doping in the ZnO matrix was observed on the lattice parameters, which were found to increase with the dopant concentration. Rods and a nanosheet-like morphology were observed via FESEM images. The ferromagnetic nature of samples is associated with the presence of bound magnetic polarons. The enhancement of saturation magnetization was observed due to Fe doping up to 3% in correspondence with the increase in the number of bound magnetic polarons with an Fe content of up to 3%. This behavior is observed as a result of the change in the oxidation state from +2 to +3, which was a consequence of Fe doping ranging from 3% to 5%. The electrode performance of Fe-doped ZnO nanostructures was studied using electrochemical measurements. The cyclic voltammetry (CV) results inferred that the specific capacitance increased with Fe doping and displayed a high specific capacitance of 286 F·g-1 at 10 mV/s for 3% Fe-doped ZnO nanostructures and decreased beyond that. Furthermore, the stability of the Zn0.97Fe0.03O electrode, which was examined by performing 2000 cycles, showed excellent cyclic stability (85.0% of value retained up to 2000 cycles) with the highest specific capacitance of 276.4 F·g-1, signifying its appropriateness as an electrode for energy storage applications.

Multifunctional properties of transition metal based double perovskite ceramics

In this manuscript, iron based double perovskite oxides Ca2Fe1-xNixNbO6(x=0, 0.1) were successfully synthesized adopting the physical mixed oxide route and high temperature annealing. The influence of Ni substitution on the structure, band gap tuning, leakage current, dielectric, energy storage and magnetic properties of the parent ceramic is also discussed. A relatively high remnant polarization of 11.8 µC/cm2 with a reduced band gap of 1.9 eV is noticed in the Ni modified ceramic. It is found that the saturation magnetization increases from 0.359 emug−1 to 0. 892 emug−1 whereas the leakage current density decreases from 6.869E−6 to 5.52E-6 A/mm2 upon Ni substitution. The enhanced saturation magnetization and ferroelectric properties of the modified ceramic with lesser leakage current increases their energy storage capacity. The energy storage efficiency of the Ni substituted material increases from 15.52% to 71% with a reduction of hysteresis loss. Hence the increase in remnant polarization and decrease in band gap of the Ni modified ceramic aligns it toward ferroelectric photovoltaic application.

Enhanced magnetic properties and leakage current mechanism in bismuth lanthanum ferrite thin films coupled with impedance and magnetic studies

A highly crystalline and pure phase Bi0.993La0.007FeO3 (BLFO) thin films have been grown using a pulsed laser deposition technique. The structural analysis confirmed the thin film is well crystallized with a rhombohedral crystal structure with an R3c space group. The BLFO phase and composition are also confirmed by transmission electron microscopy and EDAX analysis. The surface chemistry of thin films, analysed by X-ray photon spectroscopy, reveals Fe's presence in Fe3+ and Fe2+ states. At RT, the deposited film exhibited high dielectric permittivity (∼4 × 102) and low dielectric loss (∼10−1). The isothermal magnetization on highly oriented (001)-MgO and LaAlO3 (LAO) substrates is investigated. The response is compared to the randomly oriented polycrystalline films on low-cost substrates (Pt/TiO2/SiO2/Si and n-type Si substrate). The enhanced saturation magnetization of 57 emu/cm3 and 36 emu/cm3 at 10 K and 300 K are observed at 2.5 kOe applied field for the film grown on the LAO substrate. Additionally, the low leakage current density of the film is obtained around ∼1 × 10−7 A/cm2 at a field of 100 kV/cm. Acquiring single-phase BLFO thin films with enhanced electrical and magnetic properties can be relevant in designing multiferroic materials for multiple-state memories, magnetic field sensors, and spintronics applications.