Hc Values Research Articles

Investigation of the influence of Al layer and total film thicknesses on structural and related magnetic properties in sputtered Ni/Al multilayer thin films

The effects of parameters of Al layer thickness and total film thickness on the structural and related magnetic properties of Ni/Al multilayer films were investigated. The films were deposited by a dual sputtering. The Ni content decreased gradually while the Al content increased as the Al layer thickness increased. It was also observed that the total film thickness had little effect on the film content. All films have a face-centred cubic structure. And, the surface morphology of Ni/Al films is more uniform and homogeneous than the surface of Ni film. For magnetic analysis, the properties were strongly changed with the parameters. The saturation magnetisation, Ms of Ni film was obtained as 572 emu/cm3 while the Ms of the Ni/Al films decreased from 441 to 298 emu/cm3 with increasing Al content in the films caused by the Al layer thickness. And, the increase of total film thickness resulted in a decrease of Ms value. While the coercivity, Hc value of the Ni film was 90 Oe, Hc of Ni/Al films was decreased to ~ 39 Oe with the formation of multilayer structure. Ni/Al multilayers were obtained magnetically softer than the Ni film. The Ms and Hc values were significantly affected by the variation of the film content and crystal structure caused by the changes in deposition parameters. Therefore, this is a fundamental step for Ni/Al multilayers to improve the properties of these films for their potential applications in microelectronic devices.

Effects of gamma-irradiation on the superconducting properties of FeTe0.55Se0.45 single crystals grown by self-flux method

We have investigated the effect of gamma (γ)-irradiation on the structural and superconducting properties of FeTe0.55Se0.45 single crystals grown by the self-flux method. The impact of γ-irradiation on the superconducting transition temperature (TC), critical current density (JC), and vortex pinning mechanism has been systematically studied. The x-ray diffraction study reveals the growth of single crystals along the c-axis. The superconductivity has been confirmed in pristine and γ-irradiated samples through temperature-dependent resistivity (ρ(T)) and magnetization [M(T)] measurements. After irradiation, a slight improvement is observed in the upper critical field Hc2(0) values. The values of thermally activated energy have been calculated and a crossover from a single to collective vortex pinning regime is observed. Additionally, we have analyzed the vortex phase diagrams, revealing a transition from vortex liquid to vortex glass state. Furthermore, the presence of second magnetization peak (SMP) or fishtail effect has been noticed in the M(H) loops, and with increasing temperature, the position of SMP (Hsp) shifts toward lower magnetic field regions. The critical current density has been estimated by Bean's critical state model at different magnetic fields [JC(H)] and temperatures [JC(T)]. The defects through gamma-irradiation lead to a significant threefold increase in JC compared to pristine samples in self-field and at 2 K. The pinning mechanisms have been explained using collective pinning theory and the Dew-Hughes model by analyzing the normalized pinning force density. Our analysis indicates that δl-pinning is dominant and point defects are present in all the samples.

Investigation on structural, morphological, optical, magnetic properties of CdO-CoFe2O4 nanocomposites and their photocatalytic application

The nanoparticles of pure CdO and CoFe2O4 were synthesized by co- precipitation technique and the composites [(CdO)x- CoFe2O4)1−x] [(DF1 (x = 0.6), DF2 (x = 0.4), DF3(x = 0.2)] were synthesized via sono chemical route. X- ray diffraction (XRD) study validated the presence of two phases in the material. The crystallite size calculated using Debye Scherrer equation were in nano range having size from 8 nm to 59 nm. The morphological and compositional studies of the synthesized material are done by Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive Spectroscopy (EDS) respectively. EDS spectroscopy confirms the conversion of initial precursor salts into final material according to their stoichiometric ratios. The optical properties of the material were examined by ultra violet – visible (UV-Vis) Spectroscopy. Further, Tauc’s plot was employed to obtain the band gap of the material. The band gap (2.5 to 2.9 eV) falls within the range of visible light (typically 400 to 700 nm). This means that the material can effectively absorb visible light photons, which is a crucial requirement for many photocatalytic reactions. The cationic and anionic bonding at different interstitial sites was revealed by Fourier transform infrared spectroscopy (FTIR). The magnetic properties of the material were examined through Vibrating sample magnetometer (VSM). M-H curve gives information about saturated magnetization (Ms), coercivity (Hc) and retentivity (Mr) etc of the material. The maximum obtained values for Ms, Hc and Mr are 41.921 emu/g, 1651.6 Oe and 14.2 emu/g respectively, which confirm the ferrimagnetic nature of the material. The photocatalytic activity of the material under ultraviolet region is evaluated for Methylene Blue (MB) dye. The best photocatalytic results were shown by DF1 sample with discoloration efficiency of 84.5%. The active participation of hydroxyl ion (OH-) and singlet oxygen ion (O2-) is confirmed through scavenger test using Isopropyl alcohol (IPA) and Disodium ethylene diaminne tetraacetic acid (EDTA 2NA) respectively. The dye removal kinetics was tested by using various order rate models. Further to check the stability of the material, recycling efficiency of the material has been calculated for four consecutively cycle.

Analysing the effects of toluene percentages and exhaust gas re-circulation rates on spark-ignition engine performance and emissions

This study delves into the intricate dynamics of gaseous emissions in relation varying parameters in spark-ignition engines: gasoline-toluene blending ratios, exhaust gas re-circulation (EGR) rates, and spark timings. With increasing toluene concentrations, there was a consistent reduction in emissions, culminating in HC values of 67 ppm, CO at 0.6% volume, PM at 11 mg/m?, and NOx at 100 ppm for a 100% toluene blend. The implementation of EGR demonstrated its efficacy in mitigating NOx emissions, registering a decline to 60 ppm at a 30% EGR rate. However, the same augmentation in EGR rates witnessed an uptick in HC and CO emissions. Analysis of spark timings pinpointed an optimal advance of 30? CA bTDC at a 50% engine load, yielding minimized emissions. Conclusively, the research underscores the potential of fine-tuning engine parameters, such as fuel composition, EGR rates, and spark advance, to achieve a harmonious balance between engine efficiency and emission reductions. This study lays foundational data for further exploration and optimization in the realm of internal combustion engines.

Properties of High-Entropy Fe30Co20Ni20Mn20Al10 Alloy Produced by High-Energy Ball Milling.

A high-entropy Fe30Co20Ni20Mn20Al10 (at%) alloy with a face-centered cubic (FCC) crystalline phase was produced through mechanical alloying. This study examined the development of its phases, microstructure, morphology, and magnetic characteristics. Scanning electron microscopy (SEM) was applied to assess the sample morphology in relation to milling times. The changes that the material underwent during milling were investigated using X-ray diffraction. The milling time affected the phase transformation. A single FCC solid solution (crystallite size = 12 nm) was found after 50 h of milling. Additionally, the magnetic characteristics were examined and shown to be associated with microstructural changes. The powder mixture exhibited behavior consistent with soft magnetics, with an Hc value of 8 Am-1 and an Ms value of 165 emu/g. The excellent soft magnetic characteristic may be related to the stability of the FCC phase, which was generated following a 30 h milling process. In addition, the low value of Ms may have originated from the presence of Al atoms in the solid solution and the development of large densities of interfaces and crystal defects.

A-Site Doped in Perovskite La(1-x)Bax/2Srx/2Mn0.4Ti0.6O3 (x = 0, 0.1, and 0.3) for Absorbing Microwave Material

Microwave radiation can have harmful effects on our bodies. With increased exposure due to online activities, it is essential to use absorber materials like perovskite manganate to reduce radiation. In this study, perovskite manganate La(1-x)Bax/2Srx/2Mn0.4Ti0.6O3 (x = 0, 0.1, and 0.3) was synthesized using the sol-gel method. X-ray diffraction (XRD) analysis revealed that the two samples were multi-phased, LaMnO3 and La2Ti2O7, and were formed, exhibiting a rhombohedral crystal structure (R -3 c). Morphological characterization of the sample surface using a Scanning Electron Microscope (SEM) showed that as doping increases, the grain size decreases from 282.02 to 245.63 nm at x=0 and x=0.3, respectively. This result implies that doping leads to more uniform grain distribution and enhanced grain refinement. Characterization via Vibrating Sample Magnetometer (VSM) revealed that the maximum saturation value, 0.79 emu/g, was attained when x = 0. This sample exhibits soft magnetic properties, as evidenced by its coercivity (Hc) value of < 1kOe. Results from the Vector Network Analyzer (VNA) indicate that the absorption capacity of La(1-x)Bax/2Srx/2Mn0.4Ti0.6O3 increases, with a maximum reflection loss value of -25.5 dB with 1.5 mm thickness. Consequently, La(1-x)Bax/2Srx/2Mn0.4Ti0.6O3 demonstrates potential as a microwave absorber material.

Structural, magnetic and dielectric properties of green synthesized Ag doped NiFe2O4 spinel ferrite

Ag-doped nano NiFe2O4 spinel ferrites were successfully synthesized using an environmentally friendly sol-gel technique. Comprehensive characterization of the obtained samples was carried out, employing techniques such as X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The results from XRD and FTIR analyses unequivocally confirmed that the synthesized samples were of high purity and in a well-defined phase. Furthermore, examination of the samples through Field Emission Scanning Electron Microscopy (FESEM) revealed the formation of spherical grains, with an average grain size of 50 nm for pure NiFe2O4 nanoparticles and an increased size of 72 nm for the Ag-doped NiFe2O4 nanoparticles. Moreover, the investigation delved into the electrical conductivity and optical properties of these nanoferrites. It was noteworthy that the electrical conductivity demonstrated a significant enhancement in the case of Ag-doped NiFe2O4, further indicating the potential for improved performance. Magnetic analysis revealed a coercivity value (Hc) of 2.27 A/m for NiFe2O4, while the Ag-doped NiFe2O4 nanoparticles exhibited long-range ferromagnetic ordering. Additionally, optical absorption experiments disclosed an energy band gap of 1.75 eV for NiFe2O4, whereas the Ag-doped NiFe2O4 showcased a reduced energy band gap of 1.256 eV. These findings collectively contribute to a better understanding of the properties and potential applications of these materials in various technological domains.

Optical, Dielectric, Magnetic, Photocatalytic, and Antibacterial Properties of Ga-Doped BiGaxFe1-xO3 Synthesized by the Microemulsion Approach.

The effect of Ga-substitution on bismuth ferrite BiGaxFe1-xO3 (x = 0, 0.05, 0.10, 0.15, 0.20, and 0.25) properties was investigated, which was fabricated using a microemulsion route. X-ray diffraction analysis confirmed that specimens had a single-phase rhombohedral structure with space group R3̅c. The concentration of Ga had an impact on various properties such as structural parameters, crystalline size, porosity, and unit cell volume. The samples exhibited notable values for the dielectric constant, tangent loss, and dielectric loss in the low-frequency range, which declined as the frequency increased due to different polarizations. The increment in the AC conductivity was associated with rise in frequency. The P-E loops demonstrated that the samples became more resistive as the Ga concentration increased. The retentivity (Mr) and saturation magnetization (Ms) values reduced as the Ga content increased, although all samples had Hc values within the range for electromagnetic materials. The Ga-substitution had a synergistic effect on the electrochemical characteristics of BiGaxFe1-xO3, resulting in greater conductivity than that of undoped BiFeO3. These enhanced properties contributed to their higher photocatalytic activity in the degradation of crystal violet under visible light irradiation. The doped BiGaxFe1-xO3 exhibited 79% dye degradation after 90 min of illumination compared to 54% for pure BiFeO3. Recycling experiments confirmed the stability and reusability of the synthesized nanoparticles. The antibacterial activity of the samples was certified against various microbes, and the doped BiGaxFe1-xO3 showed promising activity. Thus, doped materials are good candidates for memories, dielectric resonators, and photovoltaics because of their high dielectric constant and AC conductivity, while their higher photocatalytic activity under visible light makes them promising photocatalysts for removing noxious and harmful effluents from wastewaters.

Zn-Zr induced structural and magnetic changes in strontium hexaferrite system

Polycrystalline samples of M-type Strontium hexaferrite having chemical composition SrZnxZrxFe12–2xO19 (with x = 0 and 1 and abbreviated as SFO and SZFO, respectively) were prepared successfully using solid state reaction route. The influence of calcination temperature (900 °C – 1300 °C) on the structural, microstructural, and magnetic properties of the SFO samples was explored. X-ray analysis reveals that the SFO sample is pure over the whole calcination range. The obtained X2 (goodness-of-fit; GoF) values are in the ≈ 1.02 - 1.16 range. At 1300 °C, the SFO sample develops preferred orientations along (006), (008) and (0014) crystallographic planes. The incorporation of preferred orientations leads to an improvement in the value of GoF from ≈ 4.72 to ≈ 1.16 (at 1200 °C). However, no preferred orientations are observed in the SZFO samples. Single phase Rietveld refinement is insufficient to explain the structural data. A four - phase and a three -phase refinement has been observed to be suitable in samples calcined at 1200 °C and 1300 °C, respectively. FESEM micrographs reveal a dramatic change in grain size and shape at 1300 °C in both types of samples. The best of magnetic properties has been observed at 1200 °C calcination in both types of samples. The best Mr, Ms and Hc values have been observed45.36, emu/g, 90.26 emu/g, 5032 Oe (in SFO sample) and 10.39 emu/g, 58.22 emu/g and 1181 Oe (in SZFO sample), respectively. The lower magnetic parameter values of SZFO samples can be attributed to magnetic dilution. Low temperature M-T measurements establishes the absence of magnetic nature of segregated phases in x = 1 sample.

Combustion Optimization of a Premixed Ultra-Lean Blend of Natural Gas and Hydrogen in a Dual Fuel Engine Running at Low Load

<div>The numerical study presented in this article is based on an automotive diesel engine (2.8 L, 4-cylinder, turbocharged), considering a NG–H<sub>2</sub> blend with 30 vol% of H<sub>2</sub>, ignited by multiple diesel fuel injections. The 3D-CFD investigation aims at improving BTE, CO, and UHC emissions at low load, by means of an optimization of the diesel fuel injection strategy and of the in-cylinder turbulence (swirl ratio, SR). The operating condition is 3000 rpm – BMEP = 2 bar, corresponding to about 25% of the maximum load of a gen-set engine, able to deliver up to 83 kW at 3000 rpm (rated speed). The reference diesel fuel injection strategy, adopted in all the previous numerical and experimental studies, is a three-shot mode. The numerical optimization carried out in this study consisted in finding the optimal number of injections per cycle, as well as the best timing of each injection and the fuel mass split among the injections. The analysis revealed that combustion can be improved by increasing the local concentration of the more reactive fuel (diesel): in detail, the best strategy is a two-shot mode, with SOI1 = −35°CA AFTDC and SOI2 = −20°CA AFTDC, injecting 70% of the total diesel fuel mass at the first shot. As far as the SR is concerned, the best compromise between performance and emissions was found for a relatively low SR = 1.4. The optimization permitted to extract the full potential of the H<sub>2</sub> enrichment in the DF H<sub>2</sub>/NG–diesel combustion also at low loads: in comparison to the DF NG case, combustion efficiency, and gross indicated thermal efficiency have been improved by 45.7% and 61.0%, respectively; CO- and UHC-specific emissions have been reduced by about 85.0%. Comparing CDC to the optimized DF 30 vol% H<sub>2</sub>/NG–diesel case, soot emissions are completely canceled, CO<sub>2</sub>-specific emissions have been reduced by approximately 42.0%, NO<sub>x</sub>-specific emissions by 33.8%. However, further work has to be done in order to reach comparable values of HC and CO, which are still higher than in a standard diesel combustion.</div>

Hosting capacity of distribution networks for controlled and uncontrolled residential EV charging with static and dynamic thermal ratings of network components

AbstractThe ongoing electrification of road transportation sector, which is expected to continue to strongly increase over the next years, will result in the connection of a significant number of electric vehicle (EV) chargers in LV and MV distribution networks, particularly in residential applications with on‐board (“slow”) EV chargers. In order to evaluate loading limits of existing distribution networks for the maximum number of EV chargers that can be safely connected (commonly denoted as a network EV “hosting capacity”, HC), this paper introduces a general approach to determine one commonly used network design parameter (after‐diversity maximum demand, ADMD) and one new parameter (maximum daily energy demand, MDED), which are both obtained from the load profiles of maximum per‐hour demands for uncontrolled residential EV charging. The presented approach uses actual EV charging data from the UK as the inputs in Monte Carlo simulations to generate daily EV charging profiles for arbitrary numbers of EVs, enabling to identify related ADMD, MDED and per‐hour maximum demand values, as well as their seasonal variations. The assessed ADMD, MDED and hourly maximum EV charging demands for uncontrolled EV charging are then combined with available UK residential daily load profiles before the EVs are connected (“pre‐EV demands”), where their combined coincidental and noncoincidental maximum demands are evaluated against the static thermal rating (STR) and dynamic thermal rating (DTR) loading limits of network components (transformers and overhead lines), taking into account relevant weather/ambient conditions. This is denoted as a network HC for uncontrolled EV charging. Finally, evaluating the resulting per‐hour maximum demand values against the STR and DTR loading limits and MDED values allows to select one particular scheduling method for controlled EV charging, which gives the absolute maximum number of EVs that can be safely connected in the considered network, that is, maximum network HC for fully controlled EV charging. The presented approach is illustrated on the example of the IEEE 33‐bus test network (modelled using typical UK network components), for the pre‐EV residential demands taken from the recordings at a UK MV substation, and for ambient data taken from a UK Met Office weather station. Obtained results allow to evaluate the range of network EV HC values for uncontrolled and controlled EV charging, that is, lower and upper HC limits, which can be correlated with the commonly used allocations of the firm and non‐firm network HC, respectively.

EFFECT OF Fe CONTENT ON THE STRUCTURAL AND MAGNETIC PROPERTIES OF TERNARY (Ni60Co40)100−xFex NANOMATERIALS SYNTHESIZED BY HYDROTHERMAL ROUTE

The effect of iron content on the structure, morphology and magnetic properties of (Ni[Formula: see text]Co[Formula: see text])[Formula: see text]Fe[Formula: see text] powders synthesized by hydrothermal method has been studied. Several samples have been elaborated for different Fe content ([Formula: see text] = 0, 3, 5, 7, 10 and 13.5). The as- prepared samples have been characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometry (VSM). From XRD spectra and for all Fe content, we have shown the presence of both face centered cubic (FCC) and Hexagonal (HCP) nanosized phases. The lattice parameter increases with increasing Fe content and the grains size varies with Fe content to reach a minimum value of 32 nm for (Co[Formula: see text]Ni[Formula: see text])[Formula: see text]Fe[Formula: see text]. From hysteresis curves, we have extracted the saturation magnetization, Ms, and the coercivity, Hc. We noticed that Ms increases and then decreases as a function of Fe content. The values of Hc vary from 156 Oe to 186 Oe depending on the particles shape.

Effect of The Composition of TiO2 Additives on The Physical and Magnetic Properties Crystal Structure and Microstructure of BaFe12O19 Magnetic Ceramics

<p>In this research, the manufacture of barium hexaferrite (BaFe<sub>12</sub>O<sub>19</sub>) magnetic ceramics and the addition of titanium dioxide (TiO<sub>2</sub>) additives with variations of 0%: 0.3%: 0.6% and 0.9% used the powder metallurgical method. The characterization used in this study is the measurement of density, porosity, X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Vibrating Sample Magnetometer (VSM), and Impulse Magnetizer K-Series. Based on the results of density and porosity measurements, the highest values were 4.95 g/cm3 and 5.45%, respectively. XRD results showed the formation of a BaFe<sub>12</sub>O<sub>19</sub> phase with some impurities at 0% (Fe<sub>2</sub>O<sub>3</sub>), 0.3% and 0.9% (Ti<sub>6</sub>O<sub>11</sub>), and 0.6% (Ti<sub>4</sub>O<sub>7</sub>). The SEM results showed that the morphology of TiO<sub>2</sub>-BaFe<sub>12</sub>O<sub>19</sub> was quite homogeneous, and the size and cavity ranged from 0.5 – 1.5 μm and 0.25 – 0.9 μm, respectively. VSM results show Mr, Ms, Hc, and Bhmax values of 1,489 kG, 3,235 kG, 1,758 kOe, and Bhmax of 0,867 MGOe, respectively. The results of the Impulse Magnetizer K-Series show the maximum and lowest magnetic flux values of 272.65 gauss and 218.10 gauss at 0.6% and 0% variation, respectively.</p>

Tuning the gas sensing properties of spinel ferrite NiFe2O4 nanoparticles by Cu doping

Copper substituted nickel ferrite nanoparticles (NiFe2O4) nanoparticles were prepared using hydrothermal technique at lower reaction temperature (175 °C). The structural, optical, dielectric, and magnetic properties were analyzed. The prepared nanopowders exhibited single phase-cubic spinel structure with a mean crystallite size in a narrow range 30–41 nm. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the presence of stretching vibration of metal oxide in the range 400–600 nm. Field Emission Scanning Electron Microscopy (FESEM) and High Resolution-Transmission Electron Microscopy (HR-TEM) observations showed non-uniform cuboidal shaped nano-sized particles. The chemical and oxidation state of the constituents were revealed by X-ray photoelectron spectroscopy (XPS) (Cu2+, Fe3+ and Ni2+). Mössbauer spectra manifested two sextet patterns attributed to tetrahedral (A) and octahedral (B) sites with a doublet pattern of low intensity. Magnetic measurement revealed the decrease of saturation magnetization (Ms) value and increase of remanence magnetization (Mr) and coercivity (Hc) values while doping. A higher specific capacitance was obtained for x = 0.5 (1417 F/g) with a pseudocapacitive behavior. At room temperature, Liquefied Petroleum Gas (LPG) showed high selective response (1300 s for 250 ppm) compared to other tested gases.

Unveiling the Magnetic and Structural Properties of (X2YZ; X = Co and Ni, Y = Fe and Mn, and Z = Si) Full-Heusler Alloy Microwires with Fixed Geometrical Parameters

We studied Ni2FeSi-, Co2FeSi-, and Co2MnSi-based full-Heusler alloy glass-coated microwires with the same geometric parameters, i.e., fixed nucleus and total diameters, prepared using the Taylor–Ulitovsky method. The fabrication of X2YZ (X = Co and Ni, Y = Fe and Mn, and Z = Si)-based glass-coated microwires with fixed geometric parameters is quite challenging due to the different sample preparation conditions. The XRD analysis showed a nanocrystalline microstructure for all the samples. The space groups Fm3¯m (FCC) and Im3¯m (BCC) with disordered B2 and A2 types are observed for Ni2FeSi and Co2FeSi, respectively. Meanwhile, a well-defined, ordered L21 type was observed for Co2MnSi GCMWs. The change in the positions of Ni, Co and Mn, Fe in X2YSi resulted in a variation in the lattice cell parameters and average grain size of the sample. The room-temperature magnetic behavior showed a dramatic change depending on the chemical composition, where Ni2FeSi MWs showed the highest coercivity (Hc) compared to Co2FeSi and Co2MnSi MWs. The Hc value of Ni2FeSi MWs was 16 times higher than that of Co2MnSi MWs and 3 times higher than that of Co2FeSi MWs. Meanwhile, the highest reduced remanence was reported for Co2FeSi MWs (Mr = 0.92), being about 0.82 and 0.22 for Ni2FeSi and Co2MnSi MWs, respectively. From the analysis of the temperature dependence of the magnetic properties (Hc and Mr) of X2YZ MWs, we deduced that the Hc showed a stable tendency for Co2MnSi and Co2FeSi MWs. Meanwhile, two flipped points were observed for Ni2FeSi MWs, where the behavior of Hc changed with temperature. For Mr, a monotonic increase on decreasing the temperature was observed for Co2FeSi and Ni2FeSi MWs, and it remained roughly stable for Co2MnSi MWs. The thermomagnetic curves at low magnetic field showed irreversible magnetic behavior for Co2MnSi and Co2FeSi MWs and regular ferromagnetic behavior for Ni2FeSi MWs. The current result illustrates the ability to tailor the structure and magnetic behavior of X2YZ MWs at fixed geometric parameters. Additionally, a different behavior was revealed in X2YZ MWs depending on the degree of ordering and element distribution. The tunability of the magnetic properties of X2YZ MWs makes them suitable for sensing applications.

The Depairing Current Density of a Fe(Se,Te) Crystal Evaluated in Presence of Demagnetizing Factors

The effect of the demagnetizing factor, regarding the determination of the de-pairing current density Jdep, has been studied in the case of a Fe(Se,Te) crystal, using DC magnetic measurements as a function of a magnetic field (H) at different temperatures (T). First, the lower critical field Hc1(T) values were obtained, and the demagnetization effects acting on them were investigated after calculating the demagnetizing factor. The temperature behaviors of both the original Hc1 values and the ones obtained after considering the demagnetization effects (Hc1demag) were analyzed, and the temperature dependence of the London penetration depth λL(T) was obtained in both cases. In particular, the λL(T) curves were fitted with a power law dependence, indicating the presence of low-energy quasiparticle excitations. Furthermore, by plotting λL−2 as a function of T, we found that our sample behaves as a multigap superconductor, which is similar to other Fe-11 family iron-based compounds. After that, the coherence length ξ values were extracted, starting with the Hc2(T) curve. The knowledge of λL and ξ allowed us to determine the Jdep values and to observe how they are influenced by the demagnetizing factor.

Microstructure and magnetic properties in nanocrystalline Pr2Co7-xFex alloys: Experimental and theoretical study

We report on an experimental and theoretical investigation of the microstructural and magnetic properties in nanocrystalline Pr2Co7-xFex compounds. The exchange interactions (Jij) and Curie temperature (TC) values were theoretically determined using mean field theory (MFT), and the results were found to be in excellent agreement with experimental data. The dependence of macroscopic and microscopic magnetic properties on the Fe content (x) was investigated, considering the model of random magnetic anisotropy. The saturation approach (SA) was utilized to analyze magnetization curves (M(H)), and various magnetic parameters, including random anisotropy fields (Ha) and local random anisotropy constant (K1), were studied. It was observed that these parameters increase with increasing Fe content up to x = 0.5 and then decreased for x > 0.5. Moreover, the coercivity (HC) was analyzed using the Herzer model by taking into account the grain size (D) and exchange correlation length (Rf). The experimental HC values were consistent with those derived from the random anisotropy model. Electronic structure calculations based on density functional theory (DFT) were performed to further understand the impact of Fe substitution and the improvements in magnetic performance. The collective findings provide valuable insights into the magnetic properties and behavior of nanocrystalline Ce2Ni7-type Pr2Co7-xFex compounds, aiding in the understanding and design of advanced magnetic materials.

Synthesis and tailoring the structural and magnetic characteristics of Zn–Zr substituted Sr-hexaferrite targeting diverse applications

SrZnxZrxFe12-2xO19 (x varying within 0.1–0.4) samples were prepared successfully via solid state route. Their structural characteristics (along with microstructural and magnetic) have been discussed. Rietveld refinement established the phase purity for the samples x ≤ 0.3 (goodness-of-fit <1.15) whereas the presence of ZnFe2O4 and SrZrO3 impure phases was observed in x = 0.4 sample. The three-phase model resulted in decreasing χ2 values from 1.21 to 1.05 for x = 0.4 sample. The XRD findings also reveal an increasing cell volume from 690.675 Å3 (x = 0.1) to 693.096 Å3 (x = 0.3) and a decreasing porosity from 33% to 30% on increasing ˋx’. The average grain size increases from 0.83 μm to 1.04 μm according to FESEM micrographs with increasing ˋx’. The TEM measurements reveal the presence of rod like particles (in addition to random shaped particles) in x = 0.1–0.3 samples. M v/s H studies reveal, and increase in Ms from 90.26 emu/g (for x = 0.0) to 91.41 emu/g (for x = 0.1) and a decreasing trend afterwards to 87.90 emu/g (at x = 0.3). Hc value continuously decreases from 5032 Oe (for x = 0.0) to 1903 Oe (for x = 0.4). Low temperature M − H and M-T measurements coupled with room temperature M − H measurements reveal the absence of superparamagnetic behaviour. The magnetic data suggest that all the samples possess hard ferrite characteristics and could be useful for microwave absorbers, permanent magnets as well as high-density recording media applications.

A novel magnetic NiFe2O4-Ag-ZnO hybrid nanocomposite for the escalated photocatalytic dye degradation and antibacterial activities

The eco-friendly and cost-effective NiFe2O4-Ag-ZnO (nickel ferrite-silver-zinc oxide) (NFAZnO) nanocomposite was made using an easy straightforward chemical co-precipitation method and subsequent thermal treatment process. The increased UV light-driven photocatalytic performance and enhanced antibacterial activity of the nanocomposite were reported. The structural, morphological, magnetic, and catalytic characteristics of the nanocomposite were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), photoluminescence (PL), Raman, vibrating-sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analysis. The results from XRD revealed that NFAZnO has a crystalline structure and EDAX elemental mapping confirmed the uniform distributed of all the elements in the matrix. Investigations into the microstructure found ultrafine grained structure of NFAZnO nanocomposite with an average crystallite size of 27.95 ± 0.38 nm as calculated from Scherrer’s formula. NFAZnO nanocomposite has a specific surface area of 13.56 m2/g, which is significantly more than ZnO (6.89 m2/g) as calculated from BET. At normal temperature, the magnetic characteristics showed the superparamagnetic behavior of the nanocomposite with saturation magnetization (Ms) value of 6.59 emu/g, remnant magnetization (Mr) value of 0.75 emu/g, and coercive field (Hc) value of 170 Oe. The Ag doping and addition of NiFe2O4 induces depletion in near-band edge emission, which lowers the rate of electron-hole recombination, according to the PL observations. Methylene Blue (MB) dye was subjected to photocatalytic degradation under the exposure to UV light, and according to the findings, NFAZnO nanocomposite exhibited the highest levels of photocatalytic activity with 98% degradation in just 60 min. The NFAZnO nanocomposite also showed enhanced antibacterial activity against Escherichia coli (E. coli) having zone of inhibition (ZOI) of about 28.9 ± 0.28 mm showing 123.5% activity as compared to control ampicillin having ZOI of 23.4 ± 0.13 mm, proving its applicability for both biomedical and environmental applications.

Magnetic and structural characteristics of self-assembly Co-Ni-Zn ternary nanocrystals

With respect to the rapid growth of high-performance applications for magneto-electric alloys, extensive attempts have been made to develop the electroplating of nanocrystalline magnets coatings within high coercivity and excellent corrosion resistance. Herein we proposed a low-cost and practical electroplating of the substitution of Zn2 + ions in Ni-Co bath for the ternary Ni-Co-Zn soft-magnetic alloys. Anomalous co-deposition of Ni0.12Co0.88-xZnx (x = 0–0.36) alloys were aligned from sulfamate electrolytes within L-ascorbic acid (H2Asc) as complexant, in which the ratio (x) of atomic molar was regulated by dropping ZnCl2 concentrated solution based on Nernst theory and Cyclic-Voltammetry (CV) tests. Results validated that it yielded crystal growth within a narrow size of 150–250 nm, allowing the structural recombination of the spider-web-like ZnO tangled with Ni-Co nanocrystals. In addition to the enhanced corrosion behavior of the ternary Ni-Co-Zn alloys compared to binary Ni-Co, it was attributed to the coexistence of γ-Ni5Zn21 phase and [Zn(OH)4]2- colloidal-like corrosion products. More impressively, it depicted high coercivity (Hc) of ∼15.3 Oe and superior saturation magnetization (Ms) of ∼153.2 emu/g from VSM tests for Ni0.12Co0.64Zn0.24 (x = 0.24), which was due to the self-assembly of ZnO-rich dispersoids twined around GB regions to be magnetic isolation and restrict the movement of domain walls for higher coercivity. Especially for the sample (x = 0.24) after aged at 450 °C for 2 h, it achieved a superior Hc value of 45.8 Oe that was 3 times higher than those without ageing, which was correlated well with large internal stresses by the disordered stacking among hetero-atoms. So the integrated Ni-Co-Zn ternary soft magnets offered a promising approach to achieving high coercivity with excellent anti-corrosive properties, satisfying the stringent requirements of potential applications used in magnetic memory devices, etc.