Saturation Magnetization Ms Research Articles

First-principles calculations to investigate Structural, mechanical, electronic, magnetic and thermoelectric properties of MRh2O4 (M = Mg, Mn, Cd) spinel oxides

Structural, mechanical, magnetic, electronic and thermoelectric properties of MRh2O4 (M = Mg, Mn, Cd) spinel oxides are studied through first-principles calculations. Calculations of structural and elastic stiffness constants (Cij’s) show that the MRh2O4 oxides are stable structurally and mechanically. Elastomechanical results show that the CdRh2O4 is ductile, MnRh2O4 is brittle, while MgRh2O4 lies on the borderline differentiating the ductile and brittle character. MnRh2O4 has high bulk modulus and high Young’s modulus which indicate its ability to resist plastic deformation. MnRh2O4 spinel oxide bears the highest values of Debye temperature (TD = 634.4 K) and melting temperature (Tm = 3530.4 K) among the MRh2O4 (M = Mg, Mn, Cd) oxides. Band structure calculations and density of states spectra indicate the p-type semiconducting nature of MRh2O4 (M = Mg, Mn, Cd) oxides. Spin-polarized electronic structure of CdRh2O4 show 100 % spin-polarized behavior, while MgRh2O4 and MnRh2O4 oxides show 0.12 % and 0.29 % spin-polarization, respectively. MnRh2O4 exhibits saturation magnetization Ms = 172 emu/g and total magnetic moment mtot = 9.99 µB/f.u. Temperature dependent thermoelectric properties (thermal conductivity, electrical conductivity, Seebeck coefficient, Hall coefficient, power factor and figure of merit) are also studied for MRh2O4 oxides. Calculated thermoelectric properties of MRh2O4 (M = Mg, Mn, Cd) oxides show that these oxides are promising for applications as novel thermoelectric materials.

The effect of composition on the structure, optical, and room-temperature ferromagnetic properties of hydrothermally synthesized (ZnSn)1-xCuxO nanocomposites

(ZnSn)1-xCuxO nanocomposites (NCs) with nanorods and nanosheet morphologies were synthesized by a facile hydrothermal technique. (ZnSn)1-xCuxO NCs exhibited a gradual band gap redshift from UV to visible spectral region with increasing Cu-content. The room temperature magnetic hysteresis loop indicated the improvement of room temperature ferromagnetic (RTFM) behavior of (ZnSn)1-xCuxO NCs compared with nanostructured ZnSnO NCs induced by the exchange interaction of Cu-bound polarons with the localized spins and free carriers. The (ZnSn)60Cu40O NCs exhibited the highest saturation magnetization (Ms) of 0.539 emu·g−1. Further increase in Cu-content resulted in the deterioration of crystalline domains and the reduction of Ms to 0.259 emu·g−1. This behavior revealed that the electronic and magnetic properties of (ZnSn)1-xCuxO NCs were so sensitive to the dopant concentration that need to be utilized for improving their performance as good candidate NCs for spintronic applications.

Cooperative effects due to Zn–Sn replacement by Co-ions on the optical and magnetic properties of (ZnSn)1- xCoxO nanocomposites

In the present study, the structural, optical, and magnetic properties of (ZnSn)1-xCoxO nanocomposites (NCs) were reported. The transmission electron microscope (TEM) images of ZnSnO NCs showed mixed nanorods and nanosheets morphologies that completely transformed to mostly nanocubes with Co-ions incorporation. The optical band gap (Eg) of nanostructured ZnO, SnO, and ZnSnO NCs was 3.2, 4.5, and 3.9 eV, respectively. The estimated Eg value of all (ZnSn)1-xCoxO NCs was lower than the undoped ZnSnO NCs. The nanostructured ZnO revealed poor room-temperature ferromagnetic (RTFM) behavior whereas nanostructured SnO exhibited paramagnetic behavior at low magnetic field strength followed by diamagnetic behavior at high magnetic field strength. The (ZnSn)1-xCoxO NCs exhibited strong improvement in the RTFM, where the hybrid (ZnSn)60Co40O NCs exhibited the highest saturation magnetization (Ms) of 2 emu·g−1. This value was 5-times higher than the undoped ZnSnO NCs and 2-orders of magnitude higher than the pure ZnO phase. However, with increasing Co-content up to 50 %, the Ms was reduced to 1.16 emu·g−1 demonstrating the corruption of RTFM. The present study indicated the importance of composition utilization for tuning physical properties of (ZnSn)1-xCoxO NCs and improving the performance of these NCs in optoelectronic and spintronics applications.

Improvement in the structural, magnetic and electromagnetic behaviour of barium hexaferrites with yttrium doping for EMI shielding

Electromagnetic interference (EMI) shielding is critical for protecting electronic devices from interference generated by various sources such as power lines, radio waves, microwaves, and electronic devices. In this current study, we present a thorough investigation of the structural, magnetic, and electromagnetic properties of Y3+ doped M-type barium nano hexaferrites. Polycrystalline BaFe12−xYxO19 (x = 0.0, 0.3, 0.5, 0.7, and 0.9) hexaferrites are prepared using the citrate precursor method. The results of X-ray diffraction (XRD), Rietveld refinement and Raman spectroscopy confirmed that all samples have a single-phase, and pure hexagonal crystalline structure with space group P69/mmc. This result is consistent for all the prepared compositions. The structure and dopant materials in different chemical states of the sample are determined based on the X-ray photoelectron spectroscopy (XPS) spectrum. Field emission scanning electron microscopy (FESEM) analysis showed that the particles had a distinct hexagonal morphology. The chemical composition of the prepared hexaferrites is investigated using energy dispersive X-ray analysis (EDAX). UV spectroscopy showed an inverse relationship between the molar ratio of yttrium and the band gap. Vibrating sample magnetometer (VSM) results showed a decrease in saturation magnetization (Ms) and coercivity (Hc) with increasing fraction of yttrium ions. The shielding efficiency (SE) of the synthesized hexa materials against EMI is evaluated using a vector network analyser (VNA). In particular, effective EMI shielding was observed in the frequency spectra of 8–12 GHz (X-band region). Among the tested compositions, BaFe12–0.7Y0.7O19 with a thickness of 3 mm exhibited highest SE of 80.07 dB in the X-band region. The proposed yttrium-substituted barium M-type hexagonal ferrites exhibit significant reflection loss with enhanced absorption spectrum even when applied to an extremely thin 3 mm material, making it a possible preference as the radar-absorbed compound for EMI attenuators for weather monitoring, radar tracking, air traffic management, and gigahertz antennas. Furthermore, commercial applications including long-term magnetic media for recording, storing information, etc. are possible uses of the synthesised magnetic yttrium-doped barium M-type hexagonal ferrites.

Impact of (Sm, Sr) Co-Doping at Bi-Site on the Structural, Optical, Multiferroic and Dielectric Properties of Bismuth Ferrite Nanocomposites

A series of samarium (Sm) and strontium (Sr) co-doped BiFeO3 (BFO) and pure BiFeO3 (BFO) nanocomposites were synthesized by thesol-gel auto-combustion method. The X-ray diffraction pattern of the synthesized Sr:Sm BFO nanocomposites shows a rhombohedralperovskite structure. The morphological studies revealed that synthesized Sr:Sm BFO and pure BFO exhibit a regular arrangement ofgrains. The diffuse reflectance spectra (DRS) exhibit the doping of Sr:Sm BFO reduces the optical band gap values of BFO from 2.02 eVto 1.69 eV. It was observed that the prepared Sr:Sm BFO and undoped BFO samples show G-type antiferromagnetic behaviour and thevalues of saturation magnetization (Ms) increased by increasing the Sr:Sm BFO doping concentrations at the A site of BFO lattice. Themagnitude of the dielectric constant (εr) and dielectric loss (tan δ) were increased gradually with applied frequency and by increasingdoping concentration in the BFO matrix. The significant enhancement in the dielectric parameters with increasing Sm and Sr concentrations in BFO results in improved ferromagnetic properties that could be considered a promising candidate for some advanced device applications.

Structural and Magnetic Properties of MnxZn1-xFe2O4 Prepared via Sol-Gel Method

Manganese-zinc ferrite MnxZn1-xFe2O4 (MnZnF) powder was prepared using the sol-gel method. The morphological, structural, and magnetic properties of MnZnF powder were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive X-ray (EDX), field emission-scanning electron microscopes (FE-SEM), and vibrating sample magnetometers (VSM). The XRD results showed that the MnxZn1-xFe2O4 that was formed had a trigonal crystalline structure. AFM results showed that the average diameter of Manganese-Zinc Ferrite is 55.35 nm, indicating that the sample has a nanostructure dimension. The EDX spectrum revealed the presence of transition metals (Mn, Fe, Zn, and O) in Manganese-Zinc Ferrite. The FE-SEM results of MnZnF showed uniform spherical structures. VSM was used to study the change in magnetization, the saturation magnetization, (Ms) value of the samples. The measurement of VSM indicated that the MnZnF exhibits ferromagnetic behavior with coercivity Hc (0.0014 Gauss), remanent magnetization (Mr) (0.202 emu/gr), and saturation magnetization Ms (2.69 emu/g).

Effect of divalent cations (Co2+ and Ni2+) on microstructure, physical properties and application of NdFeO3

The nanocrystalline samples Nd1–xMxFeO3 (x = 0.0 and 0.1; M: Co2+ and Ni2+) were prepared using the citrate combustion method. The X-ray diffraction (XRD) pattern confirmed that the nanoparticles were synthesized in an orthorhombic structure. The particle size of Nd1–xMxFeO3 is in the range of 29–59 nm. The selected area electron diffraction (SAED) indicates the samples were prepared in a polycrystalline nature. The samples Nd1–xMxFeO3 (x = 0.0 and 0.1; M: Co2+ and Ni2+) have antiferromagnetic behavior. The Fe3+ spins are aligned antiparallel, forming the antiferromagnetic (AFM) properties, which are affected by many factors such as the bond angle between the Fe3+ (Fe3+–O2––Fe3+) and the Dzyaloshinskii-Moriya (D-M) interaction. The doping of Co2+ and Ni2+ ions in NdFeO3 enhances the magnetic properties of the NdFeO3. The saturation magnetization (Ms) of Nd0.90Co0.10FeO3 increases 1.8 times more than that of NdFeO3. The exchange bias field (HEX) of the Co-doped sample is two times greater than that of NdFeO3. The magnetic anisotropy constant (K) of the 10% Co-doped sample increases by 11 factors compared to that of NdFeO3. The Tauc plot illustrates that the samples have a direct optical transition. The divalent cation substitution (Co2+ and Ni2+) decreases the optical band gap of NdFeO3, leading to the recommendation of using the samples Nd0.90Co0.10FeO3 and Nd0.90Ni0.10FeO3 in photocatalysis of dye degradation from water. The removal efficiencies of Cr6+ at pH = 6 are 88.06%, 85.54%, and 85.52% for the samples NdFeO3, Nd0.90Co0.10FeO3, and Nd0.90Ni0.10FeO3, respectively. The Freundlich isotherm mode is the best-fit model for NdFeO3 to adsorb Cr6+ ions from aqueous solutions.

New method of chemical synthesis for nanostructured Nd-Fe-B alloy

A new method of chemical synthesis has been developed for the nanostructured Nd-Fe-B alloy using nanoparticles of Nd2O3, Fe2O3, and Fe3BO6 powders. The nanoparticles of Nd2O3, Fe2O3, and Fe3BO6 were obtained through chemical precipitation followed by calcination. The Nd2O3 nanoparticles have a rod-like shape with a diameter of 28 nm and a length of 118 nm. The α-Fe2O3 nanoparticles have an ellipsoidal shape with an average diameter of 55 ± 11 nm. Additionally, a powder mixture of nanoparticles containing 74.4 wt% α-Fe2O3 and 25.6 wt% Fe3BO6 was obtained, and the particles exhibit an irregular shape with an average diameter of 50 ± 10 nm. A mechanism for the formation of the nanostructured Nd-Fe-B alloy from the Nd2O3, Fe2O3, and Fe3BO6 nanoparticles was proposed. It was found that during the initial stage of the reductive-diffusion process, nanopowders of NdFeO3, NdBO3, and α-Fe2O3 are formed. In the second stage of the reductive-diffusion process, nanopowders consisting of phases of 36.7 wt% Nd2Fe14B, 10.9 wt% α-Fe, and 52.4 wt% CaO are formed. After removing CaO, the obtained nanostructured Nd-Fe-B alloy consists of 76.1 wt% Nd2Fe14B, a hard magnetic phase, and 23.9 wt% α-Fe, a soft magnetic phase. The average particle size of the nanostructured Nd-Fe-B alloy is 110 ± 35 nm. The nanostructured Nd-Fe-B alloy powders exhibit the following magnetic characteristics: coercive force (Hc) of 3295 Oe, saturation magnetization (Ms) of 132.01 A·m2/kg, and residual magnetization (Mr) of 99.53 A·m2/kg.

Decolonization of MB Dye (C16H18CIN3S) under the Natural Light Using Pristine and Zn−Y Substituted CoFe2O4 as a Catalyst

AbstractCo2Fe2O4 NPs were made using the sol‐gel ignition technique employing citric acid (C6H8O7.6H2O) as a reducing agent to oxidizing agent with a ratio of 1 : 3. A thorough study of the effects of divalent Zn2+ and trivalent Y3+ ion on their structural, Infra‐red, morphological, magnetic, DC‐electrical, optical, and photocatalytic activity. All of the samples have crystallized to a cubic spinel structure with a single phase space group Fd3m, according to the analysis of the XRD pattern consisting of the intense reflections (220), (311) (222), (400), (422), (511), (440), (533), and (444). Transmission electron microscopy (TEM) suggested the particle size range of ~27 nm; and demonstrates the agglomerations on the tip of MNPs, which are ideal for increasing surface area, and infrared study verifies the spinel structure. With a decrease in the hysteresis loop for the Zn−Y ligand, the magnetic hysteresis loops demonstrate a ferrimagnetic character. With Zn−Y, magnetic characteristics are noticeably affected; saturation magnetization (Ms) 70.9133 to 59.2148 emu/g; and coercivity (Hc) 1900.30 to 193.96 Oe both exhibit a decrease. The DC‐electrical resistivity image reveals the CFMNPs′ semiconducting nature and the optical energy bandgap demonstrates a decrease from their original state. The MB dye's decolorization demonstrates the amazing deterioration in a short amount of time 20 to 80 minutes range was observed to be 35.88, 61.92, 76.40, and 94.07 %.

Facile fabrication and grain-size depended on structural behavior of Cadmium-Substituted nano Co-Ni ferrites by chemical method

In this work, cadmium doped cobalt nickel ferrites were fabricated via co-precipitation method by using high purity chlorides as precursors and ammonia as precipitate. XRD measurements of synthesized Co0.6Ni0.4-xCdxFe2O4 ferrite samples revealed that the formation of mono phase cubic spinel structure ferrite nanoparticles. The volume of unit cell, crystallite size, lattice constant, bond length, hopping length, ionic radii and microstrain were directly affected by the inclusion of Cd2+ content in Co-Ni ferrite. The crystallite size (Dxrd) of prepared ferrite samples was obtained in between 14.52 and 16.92 nm. FTIR spectra showed two main absorption bands in the frequency range of 400–600 cm−1 arising due to stretching vibrations of tetrahedral (A) and octahedral (B) sites respectively. SEM analysis showed agglomerated morphology of ferrite nanoparticles with grain size decreased from 0.85 to 0.21 μm. Raman spectroscopy confirmed that, on addition of Cd2+content, Raman band was shifted towards higher wave number side. The crystallite development in Cd doped Co-Ni ferrites was explored by X-ray peak broadening methods such as Scherer’s formula, Size-Strain plot and Williamson hall methods. XRD analysis confirmed, the crystallite size and microstrain of Co0.6Ni0.4-xCdxFe2O4 ferrites were obtained from various methods, are highly inter correlated. Saturation magnetization (Ms) was decreased from 29.92 to 23.40 emu/gm with increase of Cd doping. The coercivity was reduced from 1113 to 708 Oe with Cd concentration. This is due to the magnetic anisotropy constant of Ni2+ ion is higher than that of the Cd2+ ion.

Photo/electro catalytic green hydrogen production promoted by Ga modified Co0.6Cu0.4Fe2O4 nano catalysts

The current work concentrates on the fabrication of Ga doped Co0.6Cu0.4Fe2O4 nanocatalysts via sol-gel auto-combustion (SGA) for the production of green and sustainable source of energy i.e., hydrogen through photocatalytic and electrocatalytic routes. Single-phased cubic crystal structure with Fd3m geometry was observed through XRD patterns. FESEM images show the aggregated and spherical shaped grains with distinct grain boundaries and average grain size of 1.04 and 1.39 μm for the Co0.6Cu0.4Fe2O4, and Co0.6Cu0.4Ga0.02Fe1.98O4 nanomaterials. Soft magnetic behaviour with a coercivity (Hc) and saturation magnetization (Ms) of 235.32–357.26 Oe and 54.65–61.11 emu/g was obtained for the produced nanomaterials. The estimation of photocatalytic nature for generating H2 was conducted using the sacrificial agents i.e., 0.128 M Na2S and 0.079 M Na2SO3. The analysis focused on measuring the maximum H2 generation was achieved by photocatalysts throughout three consecutive 4-h cycles. Out of all compositions, Co0.6Cu0.4Ga0.02Fe1.98O4 nanomaterial have the highest photocatalytic activity of 16.71 mmol gcat−1. However, the electrocatalytic behaviour of prepared Co0.6Cu0.4GaxFe2-xO4 (x = 0.00–0.03) electrocatalysts were determined for HER (Hydrogen evolution reaction) reaction. The overpotential values of Co0.6Cu0.4Fe2O4, Co0.6Cu0.4Ga0.01Fe1.99O4, Co0.6Cu0.4Ga0.02Fe1.98O4, and Co0.6Cu0.4Ga0.03Fe1.97O4 catalysts at 10 mA cm−2 were −0.81, −0.85, −1.03, and 1.21 V, correspondingly. Thus, at cathode current density of 10 mA/cm−2, an elevation in overpotential was noted, which indicates that the undoped Co0.6Cu0.4Fe2O4 (x = 0.00) electrocatalyst have remarkable electrocatalytic HER activity. Consequently, owing to photo/electro catalytic water splitting traits, the prepared catalysts are highly efficient for the green hydrogen generation.

Investigation and treatment of carbon pollution in LiZn ferrite ceramics prepared by spark plasma sintering

In this study, lithium–zinc ferrite (LZF) ceramics were prepared by spark plasma sintering. Problem of carbon pollution was effectively resolved by annealing decarburization, formation of BN-coated carbon paper, and formation of protective layer of different metal foils (Ti, Mo, W, and Ta). The effects of carbon pollution and different protective layers on microstructure and dielectric and magnetic properties of LZF ceramics were studied comprehensively. Results reveal that annealing decarburization and BN-coated carbon paper could significantly improve resistance and saturation magnetization (Ms) of LZF, while real part of dielectric constant (ε′) and dielectric loss (tanδ) were significantly reduced. X-ray diffraction patterns indicate that all selected protective layers can provide good spinel-phase LZF ceramics. The utilization of metallic foil as protective layer can effectively reduce carburization, improve the resistance of LZF ceramics, and reduce ε′ and tanδ values. X-ray photoemission spectroscopy and Raman spectroscopy results reveal that cations with the highest valence state replace Fe3+ at B-site. The use of metal foil protective layer leads to the infiltration of metal ions into LZF lattice, leading to the increase in the lattice constant and decrease in the Ms value. This study deepens the understanding of carburization during SPS, providing a reference scheme for future applications.

Tailoring Mechanical and Magnetic Properties in Dual-Phase FeCoNi(CuAl)0.8 High-Entropy Alloy.

For tailoring the mechanical and magnetic properties of dual-phase high-entropy alloys (HEAs), it is crucial to understand the effect of each phase on the overall properties. In this paper, the effects of individual FCC and BCC phases on the mechanical and magnetic properties of the FeCoNi(CuAl)0.8 HEA are investigated by nanoindentation and first-principles calculations. The nano-hardness of the BCC phase is 8.73 GPa, which is nearly double the 4.60 GPa of the FCC phase, which ascribes to spherical nanoprecipitates that are only observed in the BCC phase leading to precipitation hardening. First-principles calculations on the electronic structure show that calculated saturation magnetization (Ms) of the BCC phase is 0.81 T, higher than 0.77 T of the FCC phase. An approximate yield strength and Ms can be estimated by summing the volume-fraction-weighted contributions from each phase, and are in good agreement with experimental values. It indicates that the overall mechanical and magnetic properties of the dual-phase HEAs can be tailored by tuning the volume fraction of the individual phase. Our findings are helpful to design prospective dual-phase HEAs with both good mechanical properties and soft magnetic performance by adjusting the content of each phase.

Studying the Crucial Physical Characteristics Related to Surface Roughness and Magnetic Domain Structure in CoFeSm Thin Films

This study investigated the effects of varying film thicknesses and annealing temperatures on the surface roughness and magnetic domain structure of CoFeSm thin films. The results revealed that as the film thickness increased, both the crystalline size and surface roughness decreased, leading to a reduction in coercivity (Hc) and improved magnetic contrast performance. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of cobalt (Co), iron (Fe), and samarium (Sm) within the thin films. Notably, the 40 nm Co40Fe40Sm20 thin film annealed at 200 °C exhibited lower sheet resistance (Rs) and resistivity (ρ), indicating higher conductivity and a relatively higher maximum magnetic susceptibility (χac) at 50 Hz. These findings suggest that these films are well suited for low-frequency magnetic components due to their increased spin sensitivity. The 40 nm Co40Fe40Sm20 thin film, subjected to annealing at 200 °C, displayed a distinct stripe domain structure characterized by prominently contrasting dark and bright patterns. It exhibited the lowest Hc and the highest saturation magnetization (Ms), leading to a significant improvement in their soft magnetic properties. It is proposed that the surface roughness of the CoFeSm thin films plays a crucial role in shaping the magnetic properties of these thin magnetic films.

Mg-modified Zn-Co-Fe-La nano ferrites: A study of structural, morphological, vibrational, electro-optical, dielectric and magnetic evolution

The series of Zn0.4Co0.6−xMgxFe1.9La0.1O4 (x = 0.0, 0.15, 0.30, 0.45, 0.6) nanoferrites prepared via co-precipitation technique. Scherrer and Williamson-Hall (W-H) methods were used to find the crystallite size (29.6–39.2 nm and 31.6–36.3 nm, respectively) and lattice constant was calculated (8.406–8.395 Å). Moreover, Fourier transform infrared (FTIR) spectroscopy revealed the existence of absorption bands along with functional groups. The vibrations of O2- ions at the tetrahedral and octahedral sites were shown by the Raman five active modes. DC resistivity reduced in the range of 5.2961 × 108 Ω cm to 9.6453 × 107 Ω cm for x = 0.0 to x = 0.6, respectively. The maximum DC resistivity and activation energy (0.1035 eV) were obtained at the parent sample (Zn0.4Co0.6Fe1.9La0.1O4). The optical bandgaps reduced from 2.61 to 1.47 eV, as the Mg2+ contents increased. With increasing frequency the dielectric loss and the dielectric constant decrease. The magnetic parameters such as saturation magnetization (Ms= 60.82–25.94 emu/g), remnant magnetization (Mr = 47.82–18.64 emu/g), and coercivity (Hc = 1334–511 Oe) demonstrated reducing trends with the increase of Mg2+ doping. The best magnetic behavior of the as-prepared samples suitable in microwave devices was observed for Zn0.4Co0.6Fe1.9La0.1O4 sample.

Realization of Robust and Ambient-Stable Room-Temperature Ferromagnetism in Wide Bandgap Semiconductor 2D Carbon Nitride Sheets.

Due to their weak intrinsic spin-orbit coupling and a distinct bandgap of 3.06 eV, 2D carbon nitride (CN) flakes are promising materials for next-generation spintronic devices. However, achieving strong room-temperature (RT) and ambient-stable ferromagnetism (FM) remains a huge challenge. Here, we demonstrate that the strong RT FM with a high Curie temperature (TC) up to ∼400 K and saturation magnetization (Ms) of 2.91 emu/g can be achieved. Besides, the RT FM exhibits excellent air stability, with Ms remaining stable for over 6 months. Through the magneto-optic Kerr effect, Hall device, X-ray magnetic circular dichroism, and magnetic force microscopy measurements, we acquired clear evidence of magnetic behavior and magnetic domain evolutions at room temperature. Electrical and optical measurements confirm that the Co-doped CN retains its semiconductor properties. Detailed structural characterizations confirm that the single-atom Co coordination and nitrogen defects as well as C-C covalent bonds are simultaneously introduced into CN. Density functional theory calculations reveal that introducing C-C bonds causes carrier spin polarization, and spin-polarized carrier-mediated magnetic exchange between adjacent Co atoms leads to long-range magnetic ordering in CN. We believe that our findings provide a strong experimental foundation for the enormous potential of 2D wide bandgap semiconductor spintronic devices.

Mg1-xNixGayFe2-yO4 nano catalysts for green hydrogen generation with highly efficient photo/electro catalytic water splitting applications

The production of nanomaterials for renewable energy as fossil fuel substitutes is anticipated as a viable solution to the pressing issues of environmental pollution and energy scarcity. We fixated on the development of Mg1-xNixGayFe2-yO4 (x = y = 0.0–0.03; steps: 0.01) nanocatalysts by sol-gel auto-combustion route (SGAC) for the hydrogen generation through overall photo and electrocatalytic water splitting. The spinel cubic phase with Fd3m space geometry was established from XRD results. FESEM images shows cubic and spherical formed grains with definite grain boundaries and grain size of 164 and 184 nm for the MgFe2O4 and Mg0.98Ni0.02Ga0.02Fe1.98O4 nanomaterials. Soft magnetic behavior with superior saturation magnetization (Ms) and moderate coercivity (Hc) of 2.72–29.24 emu/g and 51.23–257.86 Oe was obtained for all of the developed nanocatalysts. According to the research findings, Mg0.98Ni0.02Ga0.02Fe1.98O4 nanocatalyst shows the highest photocatalytic activity of 11.38 mmol gcat−1. The as-synthesised photocatalysts' repeatability and stability were evaluated throughout repeated runs of a 4-h reaction period conducted under identical circumstances. On the other hand, the electrocatalytic studies were carried via 3-electrode arrangement (i.e., working, counter and reference) in 0.5 M H2SO4 and 0.1 M KOH electrolytes for hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). The overpotential for the MgFe2O4, Mg0.99Ni0.01Ga0.01Fe1.99O4, Mg0.98Ni0.02Ga0.02Fe1.98O4, and Mg0.97Ni0.03Ga0.03Fe1.97O4 electrocatalysts at 10 mA/cm2 were −0.866, −0.82, −1.02 and −0.92 V. Consequently, owing to these photocatalytic and electrocatalytic water splitting traits, the prepared nanocatalysts are highly efficient for hydrogen generation. However, MgFe2O4, and Mg0.99Ni0.01Ga0.01Fe1.99O4 nanomaterials show high zone of inhibition (ZOI) against Bacillus subtilis and Pseudomonas aeruginosa and therefore, making it valuable also for biological usages.

Photocatalytic and electrocatalytic hydrogen production promoted by Nd/La substituted cobalt–nickel magnetic nanomaterials

The current work concentrates on the design of Nd/La doped Co0.7Ni0.3Fe2O4 nanocatalysts for the green, clean, and sustainable generation of hydrogen through overall photocatalytic and electrocatalytic water splitting routes using sol-gel auto-combustion route. The spinel symmetry with a Fd3m geometry and cubic polycrystalline nature was observed for the developed catalysts. Spherical formed agglomerated nanoparticles having average grain size of 127.10 and 120.08 nm was confirmed for the produced Co0.7Ni0.3Fe2O4 and Co0.7Ni0.3Nd0.02La0.02Fe1.96O4 catalysts through the FESEM results. Maximum saturation magnetization (Ms) of 64.81 emu/g and coercivity (Hc) of 1234.54 Oe were attained by undoped Co0.7Ni0.3Fe2O4 catalyst. This shows the superior magnetic behaviour of our prepared catalysts, for magnetic recording applications. The estimation of photocatalytic hydrogen production for the prepared photo nanocatalysts was conducted under ambient conditions, with an irradiation from a UV-visible light having wavelength range of 200–2400 nm. The prepared Co0.7Ni0.3Nd0.03La0.03Fe1.94O4 photocatalyst shows the maximum photocatalytic activity of 12.57 mmol gcat−1. Also, the photocatalytic hydrogen evolution, repeatability, and stability of all the prepared catalysts were analyzed at three successive cycles. The third cycle showed a little drop in photocatalytic hydrogen evolution to 11.26 mmol gcat−1 as compared to the first cycle. On the other hand, the electrocatalytic activity of produced electrocatalysts were determined towards the electrocatalytic HER via a three-electrode system in 0.5 M H2SO4 electrolyte. The produced Co0.7Ni0.3Nd0.03La0.03Fe1.94O4 nanocatalyst shows excellent electrocatalytic HER activity as compared to other samples. Hence, with photocatalytic/electrocatalytic water splitting traits, the prepared nanocatalysts are highly efficient and suitable for the production of clean and green hydrogen energy sources.

Optical, magnetic, and electrochemical properties of a fluorite-perovskite Ce0.9Gd0.1O2-∂ - La0.6Sr0.4FeO3-∂ nanocomposite synthesized by one pot sol-gel auto-combustion route

Gadolinium-doped cerium oxide (Ce0.9Gd0.1O2-∂; CGO) and strontium-doped lanthanum ferrite (La0.6Sr0.4FeO3; LSF) are well-known compounds for their application in solid oxide fuel cells, dense oxygen permeable membrane, and high-temperature ceramic reactor. The superior electro-catalytic performance of these two individual oxides or their composites is well established as it originates from multivalent cations (Ce3+/4+ and Fe2+/3+/4+) and doping-induced defects like electrons, holes, and oxygen vacancies. This work focuses on synthesizing and characterizing composite taking CGO and LSF in different weight ratios, i.e., 10:90, 30:70, 50:50, 70:30, and 90:10 by sol-gel auto-combustion process. End members CGO and LSF were also synthesized for comparison purposes. All synthesized nanopowders (single phases and their composites) were characterized with X-ray diffraction (XRD) for phase identification and Scanning electron microscopy (SEM) for elemental composition analysis. XRD and SEM results established the formation of the required phase and targeted composition. The optical properties of the materials were evaluated with the help of ultraviolet–visible Diffuse Reflectance Spectroscopy (UV–Vis DRS). Tauc's approximation measured band gap energies, and all the composites showed a very high band gap in the 4.85–5 eV range. Magnetic properties such as saturation magnetization (Ms), remanence (Mr), and coercive force (Hc) were calculated from a magnetic hysteresis loop obtained from the Vibrating-sample magnetometer (VSM) experiment at room temperature. Furthermore, the law of approach to saturation (LAS) model was applied to more precisely calculate Ms and other essential parameters. In magnetic characterization, the LSF phase fraction controls the overall magnetic property of the composites. Electrochemical behavior, such as the composites' charge storage ability and stability were tested by cyclic voltammetry and chronopotentiometry method. All the samples exhibited good stability, and the highest specific capacitance of 26 F/gm was obtained for the composite sample (CL91) when only 10 % LSF phase was incorporated in the nanocomposite.

Temperature dependent magnetic and electrical transport properties of lanthanum and samarium substituted nanocrystalline nickel ferrite and their hyperthermia applications

Structural, optical, temperature dependent magnetic and electrical properties have been investigated for the nanocrystalline NiFe1.97RE0.03O4 (RE = La3+ and Sm3+) compound. Without any signs of a secondary REFeO3 phase, the Rietveld refinement reveals a single-phase spinel structure possessing cubic symmetry for current samples. The decrease in lattice constant has been observed as a result of RE ions substitution. The TEM micrographs reveal nanosized particles with an average size of 35 ± 3 nm and 32 ± 3 nm for La3+ and Sm3+ substituted samples. EDX spectra of both samples show good compositional homogeneity. HRTEM micrographs of both samples show well resolved lattice fringes and their inter-planar spacing matches with that obtained from the Rietveld analysis of the XRD patterns. The concentration of Fe2+ and Fe3+ ions has been estimated from the XPS spectra analysis and it is found to be ∼ 22% and 78% for NiFe1.97La0.03O4 and, 20% and 80% for NiFe1.97Sm0.03O4 compound. The optical energy band gap for rare earth substituted samples is found to be more than that of pure nickel ferrite. The value of saturation magnetization (Ms) and magneto-crystalline anisotropy constant (K1) estimated from the “Law of Approach to Saturation” equation for rare earth substituted samples are found to be less than that of pure nickel ferrite. However, an enhanced value of coercivity has been observed with RE substitution. ZFC (zero field cooling) and FC (field cooling) DC magnetization curves measured at 100 Oe in the temperature range of 60–400 K reveal a combination of weak and intermediate forms of magnetic interaction between the particles for both samples. Temperature dependent analysis of saturation magnetization and coercivity employing modified Bloch’s law and Kneller’s relation supports the nanomagnetic behavior of both samples. Under an AC magnetic field of 14.92 kA/m and frequency 337 kHz, the SAR and ILP values have been found to be ∼ 331 W/g and 4.22 nHm2/kg for NiFe1.97La0.03O4 and, ∼ 241 W/g and 3.21 nHm2/kg for NiFe1.97Sm0.03O4. The dielectric relaxation data have been analyzed at various temperatures ranging from 40 to 300 0C over the frequency range 100 Hz-1 MHz using electrical impedance spectroscopy. The dielectric constant for rare earth substituted samples is found to be more and their AC conductivity is observed to be less than that of pure nickel ferrite. The analysis of temperature dependent AC conductivity employing Jonscher’s power law suggests that the charge carrier’s conduction mechanism of both samples follows the small polaron hopping mechanism below 200 0C, thereafter; it follows the correlated barrier hopping mechanism. The activation energy estimated by imaginary impedance spectra is found to be 0.411 eV and 0.398 eV for NiFe1.97La0.03O4 and NiFe1.97Sm0.03O4 which is more than that of pure nickel ferrite. The Cole-Cole plots at different temperatures suggest the presence of non-Debye-type relaxation. The modeling of Cole-Cole plots with equivalent circuits for both samples confirms the contribution of both grain and grain boundary in electrical conduction. The estimated stretching exponential factor by fitting the modified KWW (Kohlrausch-Williams-Watts) equation to the imaginary modulus curve reveals relatively more dipole-dipole interaction in NiFe1.97Sm0.03O4 than that of the La3+ substituted sample.