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Magnetite (Fe3O4) nanoparticles (NPs) of diameter 100 nm and nano-hollow spheres (NHSs) of diameter 100, 185, 250, 350, and 725 nm have been synthesized by a facile one-step template-free solvothermal technique. Silica (SiO2) coating on their surface has been carried out following the Stober method. X-ray diffraction and high-resolution transmission electron microscope images confirmed the phase and morphology of the nanostructures (NSs). Furthermore, we have investigated the terahertz (THz) wave absorption properties of SiO2@Fe3O4 shell/shell NSs in the frequency range of 0.9–2.0 THz. Detailed morphology and size-dependent THz absorption study proves that these particles can be very useful as electromagnetic shielding devices.

Herein, we report a magneto-photoluminescence study of transition metal oxide, in particular, Gd-doped (x = 0, 0.03, 0.10, and 0.15) MnFe2O4 (MnGdxFe2–xO4) magnetic nanoparticles (NPs) of average d...

Magnetic topological semimetals (TSMs) with broken time-reversal symmetry are very rare and have drawn significant attention in condensed matter physics due to their numerous intriguing topological properties. Among these various magnetic TSMs, Co

This study presents the dynamic response of an eight-noded composite plate under earthquake excitation. Koyna earthquake excitation frequency is considered for the present study. Central displacement and stresses at various positions are studied extensively. Variation in response under different boundary conditions and varying geometric conditions are presented. The ply angle in a lamina and the number of layers in a plate are also varied to observe their effect on displacement and stress. In almost all the cases, 45° lamination shows maximum displacement response, whereas 0°/90° lamination scheme always shows maximum normal stress values. On the other hand, inplane shear gives maximum response whenever a − 45° layer is present. The effect of plan dimension on displacement is also presented here. The displacement response is maximum when the plate becomes square for both cross- and angle-ply laminations. The displacement response with change in total thickness of the plate is presented in this article. The response increases drastically as the plate becomes thinner for angle and cross-ply laminations. The plate becomes unstable as the side to thickness ratio increases beyond 50. The variation of stresses for cross- and angle-ply laminated plates across their layers is reported here with different boundary conditions. A very important observation made through this comparison as a 45° clamped laminated plate should be designed under transverse shear stress, whereas the simply supported plate should be designed under inplane shear stress.

In this work we have synthesized Mn doped GdFeO3 nano-particles using a green and facile sol gel method and studied their photocatalytic, optical, vibrational and electrical properties. The Rietveld refinement of the XRD profiles suggests that all the materials have an orthorhombic Pbnm crystal structure. The transmission electron microscope (TEM) images show the decrease of the average particle size from 140 to 80 nm with the Mn concentration. The high crystallinity of the synthesized particles is confirmed from the HR-TEM images. Raman spectrum is employed to investigate the phonon modes of the materials. The optical band gap of the materials is obtained from the UV-vis reflectance spectroscopy (DRS) using Tauc relation which indicates the reduction of the band gap from 2.18 to 1.72 eV with Mn-doping. The photocatalytic activity of the materials is studied by the photocatalytic degradation of rhodamine B (Rh-B) in aqueous solution under visible light illumination. The substitution of Mn at the Fe site introduces an extra electronic state between the conduction band and the valence band which reduces the electronic band gap and enhances the Rh-B degradation efficiency. A 30% Mn doping at the Fe site (GFMO3) provides an optimum space charge width which assists to attain the maximum rate of degradation of the Rh-B dye. The doping of Mn3+ reduces the photogenerated electron and hole recombination rate and hence more charge carriers take part in the redox reaction which facilitates the photo-catalytic efficiency in GFMO3. The degradation rate enhances by a factor of 2.5 for GFMO3 as compared to pure GdFeO3. The highest photocurrent density of 1.31 μA cm−2 of GFMO3 with respect to other materials promotes the separation and transfer of the photo generated charge carriers. The possible photocatalytic mechanism of the Mn doped GdFeO3 is also critically discussed. Alternating current impedance spectroscopy is used to study the electrical properties of the synthesized materials. The increase in the conductivity with the Mn concentration is explained on the basis of the band gap reduction and this is consistent with the Smit and Wijn theory. Magnetic measurement is performed to measure the magnetization strength which is useful to separate the photocatalyst by simply using a magnet. The temperature dependent magnetization measurement suggests the anti-ferromagnetic (AFM) behaviour of the studied materials with the decrease of Neel temperature (TN) with Mn concentration. The XPS study reveals the presence of multiple oxidation states of Fe(2+/3+) and Mn(4+/3+) in these materials which facilitates the conductivity as well as the oxidation/reduction efficiency at the surface of the catalyst. The band gap reduction and its effect on the enhancement of the photocatalytic degradation efficiency with Mn doping are also discussed from the density of states calculations. Thus, this study describes a promising approach for the organic pollutant degradation by designing an efficient and stable perovskite photocatalyst.

This article deals with transient responses in terms of displacement and stresses in composite plates. Eight-node isoparametric elements with five degrees of freedom at each node are used to model the plate. First order shear deformation theory (FSDT) with proper shear correction factor is considered to simulate the strain parameters of the plate. The time history responses of the composite plates with both symmetric and anti-symmetric ply layers against different sinusoidal excitation of different excitation frequencies is computed. The effect of different boundary conditions, ply orientation, plan dimension and plate thickness are studied rigorously. Contour plot for normal stress, inplane shear stress and transverse shear stress is plotted for varying ply orientations and boundary conditions for each ply layer. Comparative studies of various stress contours across different layers in a lamina for similar loading or boundary conditions are also presented. A suggestive guideline for design engineers is also provided in terms of stress contour plot for most suitable ply angle and orientation of a composite plate.

Livestock is the main backbone of the rural economy of an agriculture-based country like India. To mitigate the economic loss due to livestock’s poor performance and illness, folk phytotherapy for livestock healthcare is still actively practiced in India. Literature survey revealed that the laterite region of eastern India, characterized by its cultural, ethnic, and biological diversities, as well as topographical uniqueness, lacks comprehensive information on ethnoveterinary medicinal knowledge. The objective of the present study includes documentation of traditional knowledge of ethnoveterinary medicine (EVM) from the northern laterite region in eastern India. Ethnoveterinary medicinal data were collected using a semi-structured questionnaire, free listing, and focus group discussions. The factor for informants’ consensus (Fic), fidelity level (FL), and cultural value (CV) index have been employed for quantitative analyses. Jaccard index (JI) was used to check the knowledge similarity. Altogether, 1,234 citations were made by 132 participants. In total, 232 recorded ethnomedicinal species are used for preparing 306 remedies to treat 79 health disorders of livestock. Recorded species are distributed in 92 families, and Fabaceae is identified as the most medicinally diversified. Uses of 24 angiospermic taxa, one pteridophyte, and two fungal species were exclusively new to the existing inventory of Indian traditional ethnoveterinary medicine. In 20 disease categories, the informant consensus (Fic) value ranges from 0.4 to 0.83. According to the FL value and use-mention factor, 23 EVM plants have been identified as the most important species in the respective disease categories. Value of CV index highlighted nine species as culturally most significant (CV ≥ 0.0025 and frequency of citation ≥20) in the laterite region of eastern India. A large extent of recorded data are quite worthy for the Indian folk veterinary medicinal repository. A handful of new data reported here and statistically justified culturally most significant species will provide the golden opportunity for bioprospecting research.

Mandal SK, Rahaman CH. 2022. Perception and application of zootherapy for the management of cattle diseases occurred in northern laterite region of West Bengal, India. Asian J Ethnobiol 5: 12-19. The present study aims to invent the glory of traditional knowledge about zootherapy for livestock diseases in the northern laterite region of West Bengal, India. Semi-structured and open interviews were taken for data collection. Data were analyzed with statistical indices like use mention factor (UM) and use value index (UV). A total of 21 zoological specimens have been recorded. Mammals are the most common species (8 species) used in this region for livestock health care. It has been found that in 57% of cases, endo- & exoskeletal structures like bone, feather, horn, scale, shell, beak, teeth, etc., are used as ethnoveterinary medicine. Four species have been identified as the most frequently used species in the region are Coracias benghalensis (Linnaeus, 1758) (UM=16; UV=0.12), Herpestes javanicus palustris (Ghose, 1965) (UM=12; UV=0.09), Varanus bengalensis (Daudin, 1802) (UM=11; UV=0.08) and Lamellidens marginalis (Lamarck, 1819) (UM=11; UV=0.08). Among the recorded species, more than 50% are enlisted in the IUCN Red List. The present study provides baseline information regarding the depth of ethnozoological knowledge and its current status in the studied area, which will further help frame some conservation strategies for the medicinally important and threatened animal species.

Multiferroic materials with good magneto-electric coupling are of great interest due to their enormous applications in the field of spintronic devices. Magnetoelectric (ME) gallium ferrite is an interesting material due to its room temperature (RT) piezoelectricity and near RT ferrimagnetism along with significant ME coupling (10−11 s/m at 4.2 K). The work aims to increase the magnetic transition temperature (TC) of the material above RT so that the material can have strong ME coupling at room temperature and can be implemented for practical applications. Several earlier reports have shown the magnetic transition temperature of Ga2−xFexO3 increases with higher Fe contents. Hence, we chose to study the properties of Ga2−xFexO3 (GFO) only for x = 1.2. Y3Fe5O12 (YIG) is another material that is RT ferromagnet material with very high resistivity (∼1012 Ω cm). In this work, by forming a GFO-YIG composite with only a 10% concentration of YIG, the phase transition temperature is increased beyond room temperature from ∼289 K for GFO to ∼309 K for 0.9 GFO-0.1 YIG. The remnant magnetization is also enhanced from 0.211 emu/g to 2.82 emu/g reporting a magnetization of ∼8.2 emu/g at 30 kOe.

We report a giant exchange bias (EB) field of about 3.68 kOe during field cooled process in all

Carbon monoxide (CO), being a highly toxic gas, bears hazardous effects on human health and contributes majorly to environmental pollution. It is mostly produced by automobile exhausts and incomplete combustion of carbon-containing substances. Thus, the development of catalysts for CO conversion is highly imperative and has always gained interest for real field applications. Besides the high oxygen storage capacity and facile transitions between oxidation states, the huge abundance of cerium on earth makes CeO2 a low-cost and highly effective alternative to noble metal catalysts for CO oxidation. The present work delineates the room temperature synthesis of flower-shaped 3D CeO2 nanostructures using a sonication-assisted simple synthesis method within 2 hours under the pivotal importance of a structure-directing agent, polyvinylpyrrolidone (PVP). The bifunctional contributions of PVP as a surfactant and as a capping agent are discussed with a plausible mechanism. The method leading to the formation of hierarchical CeO2 nanoflowers provides an appreciable surface area of 132.69 cm2 g−1. The morphological and structural characterizations of the catalyst were thoroughly investigated using FESEM, TEM, XRD, UV-visible spectroscopy, photoluminescence spectroscopy, FTIR spectroscopy and X-ray photoelectron spectroscopy. The structural efficacies of flower-like CeO2 nanostructures have also been correlated to the narrowing of the band gap and the generation of the corresponding oxygen vacancies, resulting in surface catalytic properties towards 80% conversion of CO.

In search of lightweight, broadband and stable microwave absorbing material, here we have presented a morphology dependent study of microwave properties on Nickel Ferrite (NFO). A comparative study of permittivity (e), permeability (μ), Reflection Loss (RL) and Shielding efficiency (SE) on NFO nano hollow spheres (NHS) with its nano particles (NPs) and bulk counterpart has been performed for widely used X-Band (8–12 GHz) on composites filled (25 wt% and thickness of 2 mm) with each sample. Interestingly, NFO nano hollow spheres (NHS) are found to be highly efficient material towards microwave attenuation. An optimal RL of ∼−59.2 dB is obtained for frequency ∼11.7 GHz with a broad band-width (W) of ∼(9.18–12) GHz having RL 90%). Hollow cavity of NHS leads to a lower density (∼3.91 g/cc) as well as multiple internal reflections, which enhances wave absorption. Excellent impedance matching with free space, accompanied by proper dielectric and magnetic loss contributes towards maximization of RL for NHS. These properties enhance the potentiality of NFO NHS as an efficient microwave absorbing material suitable in various microwave devices.

To understand the effect of particle size on magnetorheological effect two magnetorheological (MR) fluids, composed of nano-hollow spheres (NHSs), of diameters 250 nm (MRF250) and 700 nm (MRF700), are studied. The results are compared with their solid counterpart with Fe3O4 nanoparticles (NPs) based MR fluid of 100 nm diameter (MRF100). To understand the MR mechanism the flow curves (shear stress vs shear rate) are fitted with different established models and our samples are found to follow the Bingham Plastic model. The yielding behavior of the MR fluids is found to be morphology dependent. The MR fluid with larger particles show maximum yield stress ∼830 Pa at an applied field 0.4 T, due to the combined effect of larger surface area and higher magnetism. Hollow nano spheres show better stability than that of NPs due to compatible density with the carrier fluid.

Herein, we report an easy and scalable chemical bath deposition and spin coating route of n-n hetero-architecture engineering to fabricate MoO3-ZnO core-shell nanorods (NRs) based photoanode, which is indeed the first time demonstration of this particular nano-heterojunction for solar energy conversion and hydrogen energy generation in a photoelectrochemical (PEC) cell. We further tune the MoO3 shell thickness by varying spin coated layer thickness. An average thickness ∼100 nm of MoO3over 450 nm ZnO NRs significantly improves the photocurrent from 3.3 to 27.6μAcm−2. A 7.5 fold increase in applied bias photon to current conversion efficiency (ABPE) value is achieved upon visible light illumination (Visible light, 10 mWcm−2) with a maximum value of 0.15% than bare ZnO NRs (0.02%). In addition, hydrogen gas (5 μmolcm−2) is evolved even at no external potential applied to the PEC cell with this MoO3-ZnO. The physical insight of the enhanced PEC performance is also elucidated. We find the n-n hetero-architecture to provide a suitable solution to maximize solar light absorption along with enhanced charge carrier separation which also boosts the charge transportation and mobility in the junction region due to suitable core-shell interfacial band alignment and modulation of interfacial electronic structure. Mainly, the MoO3 shell provides a potential solution to get more catalytically active sites and the outer Mo-O dipole layer transfers holes to the electrolyte for easy oxidation of water.

We synthesized ZnxFe3−xO4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 1.0) nano-hollow spheres (NHSs), a promising functional magnetic material for bio-medical applications. Detailed temperature dependent magnetic studies indicate an increase in saturation magnetization (MS) with Zn doping, attaining a maximum at x = 0.2 (MS = 92.52 emu/g at room temperature), due to the replacement of antiferromagnetically coupled FeA3+ ion on the A site by Zn2+ and transformation of FeB2+ to FeB3+ on B site for maintaining the charge neutrality. The dynamic magnetic properties of the powdered ZnxFe3−xO4 samples were investigated using frequency dependent real and imaginary parts of ac susceptibility. The data obtained by fitting Vogel Fulcher law indicates reduced dipolar interaction in our systems due to Zn doping. Applications of Fe3O4 nanostructures can be improved by doping Zn and making hollow spheres.

Magnetic topological semimetals (TSMs) with broken time-reversal symmetry are very rare and have drawn significant attention in condensed matter physics due to their numerous intriguing topological properties. Among these various magnetic TSMs, Co2-based full Heusler compounds are of current interest, since a few of these materials exhibit Weyl and nodal fermions in their topological band structure. In this work, we report a comprehensive study of anomalous Hall effect (AHE) in the ferromagnetic full Heusler compound Co2VAl. Recent studies indicate that the intrinsic AHE is closely related to the Berry curvature of the occupied electronic Bloch states. The present study of Co2VAl attempts to understand and explore the possibility of topology-induced AHE. The anomalous Hall resistivity ρ x y A is observed to scale quadratically with the longitudinal resistivity ρ xx . Our experimental results also reveal that the anomalous Hall conductivity (AHC) is ∼85 cm−1 at 2 K with an intrinsic contribution of ∼75.6 S cm−1, and is nearly insensitive to temperature. The first principle calculations note that the Berry curvature originated from a gapped nodal line and symmetry-protected Weyl nodes near the Fermi level ( E F ) is the main source of AHE in this compound. Thus, this investigation on Co2VAl discloses that it is a ferromagnetic Weyl and nodal-line TSM. The theoretically calculated AHC is in well agreement with the experimentally obtained AHC.

In this work we have synthesized Mn doped GdFeO3 nano-particles using a green and facile sol gel method and studied their photocatalytic, optical, vibrational and electrical properties. The Rietveld refinement of the XRD profiles suggests that all the materials have an orthorhombic Pbnm crystal structure. The transmission electron microscope (TEM) images show the decrease of the average particle size from 140 to 80 nm with the Mn concentration. The high crystallinity of the synthesized particles is confirmed from the HR-TEM images. Raman spectrum is employed to investigate the phonon modes of the materials. The optical band gap of the materials is obtained from the UV-vis reflectance spectroscopy (DRS) using Tauc relation which indicates the reduction of the band gap from 2.18 to 1.72 eV with Mn-doping. The photocatalytic activity of the materials is studied by the photocatalytic degradation of rhodamine B (Rh-B) in aqueous solution under visible light illumination. The substitution of Mn at the Fe site introduces an extra electronic state between the conduction band and the valence band which reduces the electronic band gap and enhances the Rh-B degradation efficiency. A 30% Mn doping at the Fe site (GFMO3) provides an optimum space charge width which assists to attain the maximum rate of degradation of the Rh-B dye. The doping of Mn3+ reduces the photogenerated electron and hole recombination rate and hence more charge carriers take part in the redox reaction which facilitates the photo-catalytic efficiency in GFMO3. The degradation rate enhances by a factor of 2.5 for GFMO3 as compared to pure GdFeO3. The highest photocurrent density of 1.31 μA cm-2 of GFMO3 with respect to other materials promotes the separation and transfer of the photo generated charge carriers. The possible photocatalytic mechanism of the Mn doped GdFeO3 is also critically discussed. Alternating current impedance spectroscopy is used to study the electrical properties of the synthesized materials. The increase in the conductivity with the Mn concentration is explained on the basis of the band gap reduction and this is consistent with the Smit and Wijn theory. Magnetic measurement is performed to measure the magnetization strength which is useful to separate the photocatalyst by simply using a magnet. The temperature dependent magnetization measurement suggests the anti-ferromagnetic (AFM) behaviour of the studied materials with the decrease of Néel temperature (TN) with Mn concentration. The XPS study reveals the presence of multiple oxidation states of Fe(2+/3+) and Mn(4+/3+) in these materials which facilitates the conductivity as well as the oxidation/reduction efficiency at the surface of the catalyst. The band gap reduction and its effect on the enhancement of the photocatalytic degradation efficiency with Mn doping are also discussed from the density of states calculations. Thus, this study describes a promising approach for the organic pollutant degradation by designing an efficient and stable perovskite photocatalyst.

Ferrite nano-hollow spheres (NHS) are of great significance to improve electromagnetic (EM) wave absorption performance. Herein, the deposition of dielectric SiO2 and ferrimagnetic CoFe2O4 (CFO) layers on MnFe2O4 (MnFO) NHS are found as an effective strategy to enhance EM wave attenuation. EM wave absorption properties of as-synthesized bare and bi-layered samples are investigated within a widely-used frequency range of 1–17 GHz. MnFO@CFO bi-layered NHSs exhibit an excellent reflection loss (RL) of −47.0 dB at only 20 wt% filler content with an effective broad bandwidth (BW) of ∼2.2 GHz (frequency region for RL −1 to 457.8 Np m−1 for bare MnFO and MnFO@CFO NHSs respectively. Larger interfacial area, additional pairs of dipole, higher magnetic anisotropy, internal reflections and scattering from NHSs are responsible for superior absorption properties of MnFO@CFO NHSs. Moreover, the best impedance matching, ∣Z in /Z 0 ∣ ∼ 1, promotes the optimum RL in MnFO@CFO at 5.96 GHz. MnFO@SiO2 bi-layered NHSs result in a sufficiently high RL ∼ −30.0 dB with a composite absorber of a thickness of only 3 mm. Analysis from the λ/4 model for best matching thickness (t m ) displays a good agreement between experimental and simulated t m values. This study demonstrates optimized MnFO@CFO NHS as a highly promising low-cost and lightweight EM wave absorber suitable for practical high-frequency applications.

The coincidence of magnetic and structural transitions near room temperature is observed in (MnNiSi)1− x(FeNiGa) x ( x = 0.16 and 0.17) systems, which leads to a coupled magnetostructural transition (MST) from a high-temperature paramagnetic Ni2In-type hexagonal phase to a low-temperature ferromagnetic TiNiSi-type orthorhombic phase associated with a substantial change in magnetization and a large change in structural unit cell volume, and thus, across MST, a giant magnetocaloric effect is obtained in these systems. The alloys with x = 0.16 and 0.17 are observed to show a giant isothermal magnetic entropy change (ΔSM) of about −26.2 and −63.2 J kg−1 K−1, accompanied with a large relative cooling power of about 220.1 and 264.5 J/kg, respectively, due to a magnetic field change ( μ0Δ H) of 5 T only. Moreover, the material with x = 0.16 and 0.17 shows a large temperature average magnetic entropy change of about −21.64 and −34.4 J kg−1 K−1 over a temperature span of 10 K due to μ0Δ H ∼ 5 T. Thus, these low-cost materials with giant magnetocaloric responses are highly suitable to be used as magnetic refrigerants for room temperature solid-state-based cooling technology.

A control methodology is presented here to generate and support active as well as reactive power flow from the photovoltaic (PV) system. This system ensures maximum active power extraction from PV system for the load and reactive power support for the grid. Two-stage method is applied for better utilization of PV system. In first stage, DC/DC boost converter is considered and the Perturb and Observe (P & O) algorithm plays important role in extracting maximum power from PV system. In second stage, a power controller is implemented for conversion of DC power to AC power. A current controller along with a dc-link voltage regulator acts as active power controller and current controller along with a sensing unit which senses the quadrature component of the load current acts as a reactive power controller. Active power and reactive power along with voltage and current at different stages of the system have been observed. The system efficiency is found to be approximately 97%.

Choice of materials is the prime step toward device applications as the unique physical and chemical properties of each material determine the desired output and efficiency of a product. Devices those are commonly used can be categorized as sensors and detectors, solar cells, fuel cells and batteries, data storage, optoelectronic and displays, resistors, switches, and among others. Fabrication of such devices to achieve optimal efficiency is an ongoing process and it is seen that effectiveness of such devices depends on the material synthesis process, mode of deposition, nucleation temperature, and inherent properties of the materials used. The most common materials which have found its way into a variety of applications are the oxides; many of them are nontoxic, economical, and easy to synthesize. So, one can notice the use of the simple binary oxides as gas sensing elements, varistors, photocatalysts, in solar cell, as conducting materials, and others. Sulfides and chalcogenides, on the contrary, are more useful as light-emitting material, in solar cell, batteries, and infrared filters. Similarly, NiO/SiO2 multilayers are used as resistive switching devices; γ-Fe2O3 and Fe3O4 are immensely popular in magnetic recording media. In this article, a list of materials, for example, oxide, sulfides, chalcogenides, graphene, magnetic, glass, piezoelectric, and ferroelectric materials, are compiled which are used as important elements in a variety of devices. Besides, the description of multiple synthesis techniques is provided in order to showcase the versatility of wet (solution) chemical method. The advantage of the chemical method is that it is easy, economical, and offers stoichiometric and morphological control, and wide ranges of materials can be produced by varying simple reaction conditions. In this article, it is revealed that the morphology and stoichiometry of the solution-processed material are related to the choice of solvents, surface compositions and ligands, particle-particle interaction, deposition methods, and nucleation. Short notes on these chemical routes toward preparing a variety of materials are presented here.

Magnetic and structural transitions are observed to coincide at around room temperature in transition-metal-based $(\mathrm{Mn}\mathrm{Ni}\mathrm{Si}{)}_{1\text{\ensuremath{-}}x}(\mathrm{Fe}\mathrm{Co}\mathrm{Ga}{)}_{x}$ (x = 0.15 and 0.16) alloys, which leads to a coupled first-order magnetostructural transition (MST) from paramagnetic hexagonal to ferromagnetic orthorhombic structure, and, as a result, a giant magnetocaloric effect is observed in these alloys. With subsequent doping for x = 0.17, the MST decouples into two separate transitions, structural and magnetic, although the transitions couple upon enhancing the applied magnetic field. The alloys with x = 0.15, 0.16, and 0.17 are found to exhibit isothermal magnetic entropy changes ($|\mathrm{\ensuremath{\Delta}}{S}_{M}|$) as large as about $25\phantom{\rule{0.1em}{0ex}}\mathrm{J}\phantom{\rule{0.1em}{0ex}}{\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{0.1em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at 323 K, about $31.1\phantom{\rule{0.1em}{0ex}}\mathrm{J}\phantom{\rule{0.1em}{0ex}}{\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{0.1em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at 281 K, and about $23.8\phantom{\rule{0.1em}{0ex}}\mathrm{J}\phantom{\rule{0.1em}{0ex}}{\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{0.1em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at 213 K, respectively, due to a field change of \ensuremath{\Delta}H = 50 kOe. These low-cost materials may be considered as promising candidates for magnetic refrigeration around room temperature due to their giant magnetocaloric properties, with significantly large relative cooling power (RCP = 191.8, 209.6, and 139.2 J/kg, respectively, for x = 0.15, 0.16, and 0.17 due to \ensuremath{\Delta}H = 50 kOe).

From the detail morphology dependent studies, nano-hollow spheres (NHS) of NiFe2O4 (NFO) are found to exhibit better magnetic and dielectric properties compared to their nanoparticles and bulk counterparts. Prepared by solvothermal method, these NHS with diameter of ∼228 nm and much lower tap density of ∼3.91 g/cc, show excellent magnetic properties with MS and HC, 63.5 emu/g and 122 Oe respectively. Variation of dielectric properties such as permittivity (e), dielectric loss (tanδ) and ac conductivity (σac) of these NHS with frequency and temperature is explained on the basis of Maxwell-Wagner two layer model for space charge and hopping of charges from Fe3+ to Fe2+ as well as Ni2+ to Ni3+ ions at B (octahedral)-sites. The complex impedance spectroscopy study indicates the presence of grain and grain boundary effects in NHS and the conduction mechanism is explained by Jonscher's power law. A comparatively low value of the activation energy (E = 0.325 eV) is found for these NHS. High value of magnetic and dielectric properties of NFO NHS enhance their potential applications for microwave devices in the form of isolators, circulators etc.

Carbon monoxide (CO), being a highly toxic gas, bears hazardous effects on human health and contributes majorly to environmental pollution. It is mostly produced by automobile exhausts and incomplete combustion of carbon-containing substances. Thus, the development of catalysts for CO conversion is highly imperative and has always gained interest for real field applications. Besides the high oxygen storage capacity and facile transitions between oxidation states, the huge abundance of cerium on earth makes CeO

Hematite (α-Fe2O3) photoanode suffers from significant photocarrier recombination and sluggish water oxidation kinetics for photoelectrochemical water splitting. To address these challenges, this work demonstrates the construction of dual co-catalysts modified Fe2O3 nanorods photoanode by strategically incorporating CoPi and Co(OH) x for photoelectrochemical water oxidation. The Fe2O3/CoPi/Co(OH) x nanorods photoanode exhibits the lowest ever turn-on potential of 0.4 V RHE (versus reversible hydrogen electrode) and a photocurrent density of 0.55 mA cm−2 at 1.23 V RHE, 358% higher than that of pristine Fe2O3 nanorods. The dual co-catalysts modification enhances the light-harvesting efficiency, surface photovoltage and hole transfer kinetics of the hybrid photoanode. The dual co-catalyst coupling also increases the carrier density and significantly reduces the depletion width (1.9 nm), resulting in improved conductivity and favorable band bending, boosting photogenerated hole transfer efficiency for water oxidation.

Herein, the magnetic, exchange bias (EB), and magnetocaloric properties of polycrystalline Ni48Co1.5Mn35Sn15.5− x Si x ( $x=1$ , 2, and 4) Heusler alloys have been investigated by magnetic measurements. All these alloys are found to undergo a first-order structural phase transition from martensite to austenite along with a second-order ferromagnetic to paramagnetic transition. It is observed that martensitic transition temperature shifts to lower temperature with increasing Si substitution in place of Sn, whereas the Curie temperature is insensitive to the doping amount. Magnetic entropy change ( $\Delta S_{M}$ ) and net relative cooling power are measured across martensite to austenite transition and the corresponding values are found to 10.86, 5.46, 2.42 Jkg−1K−1 and 122.7, 144.5, and 63 Jkg−1 for $x=1$ , 2, and 4 alloys due to a field change of 50 kOe, respectively. Interestingly, with increasing Si substitution in place of Sn, hysteresis loss reduces significantly from 52.1 J/kg ( $x=1$ ) to 8.62 J/kg ( $x=4$ ). However, the EB property of these alloys does not change significantly due to the doping amount.

Herein, we report the observation of unusual electronic and magnetic phases in traditional antiferromagnetic Co3O4 micromaterials and modulation of their properties on a temperature scale. In particular, we demonstrate a comparative low-energy carrier dynamics of Co3O4 microflower and microhollow flower (MHF) structures of same average size of 2 μm to unravel the ground-state information induced by surface electronics across the insulator-semiconductor transition using terahertz (THz) time domain spectroscopy. Interestingly, the THz optical constants of these structures are found to exhibit remarkably distinct features both as a function of frequency and temperature. Detailed study reveals that the partial metallization through large two-dimensional surface electronic states of MHF structure enables to achieve significantly higher carrier dynamics in contrast to its wide-band-gap solid counterparts and the magnetic measurements reconfirm the presence of these surface states by indicating ferromagnetism in Co3O4 MHF structures. Moreover, the simultaneous existence of insulator-semiconductor and antiferromagnetic-paramagnetic transitions near the Neel temperature points out the significant role of magnetically active Co2+ ions at the tetrahedral site of Co3O4 normal spinel structure in determining the conduction dynamics instead of 3d band related to Co3+ ions at octahedral site. Finally, we demonstrate that the continuous modulation of temperature-controlled charge transport coupled with intrinsic phase transition in Co3O4 microstructures has the potential to design efficient analog-like THz modulator, filter, and sensor. We believe that these outcomes can stimulate new opportunities toward next-generation caloritronics-based ultrafast energy-efficient transition-metal oxide electronics having both economic and environmental significance.

We report the magnetic and magnetocaloric properties of Mn48-xFexNi41Sn11 (x = 8.5, 10.5) Heusler alloys. The temperature dependent magnetization curve (M vs T curve) reveals that these alloys show only second order ferromagnetic (FM) to paramagnetic (PM) transition at their Curie temperature (TC) and no structural transformation is observed. A large value of saturation magnetization (MS) ∼ 72.76 Am2/kg is observed at 80 K for x = 8.5 alloy as the alloy becomes purely austenite for this composition. A reversible magnetic entropy change of 1.02 JKg−1K−1 with moderate refrigerant capacity (RC) ∼ 40.2 J/kg are obtained near room temperature (∼305 K) for x = 8.5, across its TC due to a field change of 14 kOe only. The critical exponents are calculated for both the samples and found to exhibit long range ferromagnetic ordering in their austenite phase.

An in-depth magnetic characterization of Dioctyl sodium sulfosuccinate (AOT) functionalized cobalt-ferrite nanoparticles (CFNPs) with average sizes from 12 to 22 nm, synthesized by co-precipitation of metal precursors, are discussed here. The $M$ – $H$ hysteresis loop at room temperature for different particle size reveals that the coercivity ( $H_{c}$ ) value reaches the maximum (4.1 kOe) at a critical size of 17.4 nm. Furthermore, magnetic relaxation ( $M$ versus time) measurements indicate relatively high value of magnetic relaxation time constant ( $\tau$ ) for AOT-assisted CFNPs. Therefore, high $H_{c}$ , significant saturation magnetization coupled with high $\tau $ ensure the permanent magnetic characteristic of the material which have the potential to replace the expensive rare-earth-transition metal-based permanent magnetic materials. On the other hand, materials with comparatively low value of $H_{c}$ , remanent magnetization will be useful for biomedical applications.

Herein, we report the origin of inherent multicolor photoluminescence in functionalized and surface modified ErFeO3 nanoparticles. Moreover, we have found unprecedented photocatalytic property of functionalized ErFeO3 nanoparticles in the degradation of a model water-contaminant. Along with theoretical confirmation and careful investigation through UV–visible absorption and fluorescence study says that the ligand-to-metal charge-transfer from tartrate ligand to the lowest unoccupied energy levels of Fe3+ or Er3+ metal ions in the NPs and f-f transitions (Er3+) play the key role in the emergence of multiple photoluminescence from the ligand functionalized ErFeO3 NPs.

We report a giant exchange bias (EB) field of about 3.68 kOe during field cooled process in all-d-metal Ni40(FeCo)4Mn36Ti20 Heusler alloy. The study of magnetic memory effect and isothermal magnetic relaxation processes suggest that the giant EB field arises due to the possible coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) phase exchange interaction in the studied system at temperatures below 35 K. Furthermore, the temperature and cooling field dependence of EB effect are analyzed which are related to the change in unidirectional anisotropy at FM/AFM interface. The study of a well-established training effect confirms the intrinsic nature of the observed EB behavior. This result will open up a new way toward the development of EB materials considering all-d-metal Heusler alloy systems.

We synthesized biocompatible NiFe2O4 nanoparticles (NPs) with diameters below 10 nm by coating their surface with a tartrate ligand, which interestingly give rise to photoluminescence covering the entire visible region. The analyses with various spectroscopic tools reveal that the reason behind the unique fluorescence properties of functionalized NiFe2O4 NPs is ligand-to-metal charge-transfer transition from the highest occupied energy level of tartrate ligand to the lowest unoccupied energy level of Ni2+ and d–d transitions centered over Ni2+ ions in the NPs. These fluorescent NPs are also found to be suitable for cell imaging. Moreover, the functionalized NiFe2O4 NPs show a good catalytic activity on biologically and environmentally toxic pigments, such as bilirubin and methylene blue which leads to their wide application towards therapeutics and waste water treatment. We believe that the developed multifunctional NiFe2O4 NPs would stimulate the opportunities for advanced biomedical applications.

Here, we reported the synthesis of bilayered BiFeO 3 /CoFe 2 O 4 nano-hollow spheres (NHSs) by depositing a BiFeO 3 (BFO) layer of thickness ∼20 nm on CoFe 2 O 4 (CFO) nano-hollow spheres surface of diameter ∼250 nm and investigated their electric, magnetic and magnetoelectric properties in view of their applications in electronic and magnetic devices. The nano-composites exhibit better properties compared to their individual counterpart. The maximum polarization in CFO/BFO NHSs is found to be 2.1 µC/cm 2 at a frequency 50 Hz. Magnetic measurements show the saturation magnetization to be 30.1 emu/g with high value of remnant magnetization (17.9 emu/g), and coercivity (1320 Oe). Its magnetoelectric coefficient, α ME at 1 kHz is estimated to be ∼8.6 mV/cm Oe.

MnNiSi-based compounds exhibit giant isothermal magnetic entropy change (ΔSM) across their induced first-order coupled magnetostructural transition (MST) in the vicinity of room temperature, though in most of the cases, the use of Maxwell relation from a very frequently used but incorrect measurement protocol provides a nonphysical spike to the calculated ΔSM. Herein, to realize the accurate measurement protocol, we explore magnetocaloric properties of a (FeCoGa)x doped (MnNiSi)1−x compound with x = 0.165 rigorously. Several methods, including the estimation of ΔSM using Maxwell relation, Clausius-Clapeyron equation, and also from the calorimetry measurement, are discussed explicitly. The studied material is observed to show a MST at 265 K and a giant ΔSM as large as about −29.3 J kg−1 K−1 due to a magnetic field change of 5 T following the Maxwell equation during discontinuous cooling and field increasing mode, which enables the material as a promising candidate for magnetic refrigeration.

In search of light-weight, stable, cost-effective and efficient microwave absorbing material, here, we have investigated electromagnetic wave (EM) attenuation properties of transition metal based MFe2O4 [M = Mn, Fe, Co, Ni, Cu, Zn] nano-hollow spheres in-detail within a widely-used frequency range of 1–20 GHz. The divalent cation, M2+ [M = Mn, Co, Ni, Cu, Zn] substitution in Fe3O4 displays a clear enhancement of EM absorption properties compared to traditional magnetite where MnFe2O4 NHS is found to exhibit an optimal reflection loss (RL) of about − 32.7 dB, total shielding efficiency (SETotal) ~ −42 dB and a high attenuation constant (α) ~ 196 Np/m. Favorable impedance matching, significant dielectric and magnetic loss contribute to the enhancement in absorption properties. Interestingly, with increase in filler concentration (in epoxy resin matrix) from 0 wt% to 50 wt%, MnFe2O4 NHS shows a gradual increase in RL values and an excellent RL of about − 45.6 dB at thickness ~4.2 mm is obtained for 50 wt% composite with a total effective bandwidth (RL 90%) of ~3.6 GHz. Moreover, analysis of quarter-wavelength model for best matching thickness (tm) displays a good agreement between experimental and simulated tm values. The overall results indicate that ferrites in the form of hollow structures are much more efficient than their bulk counterpart and optimized MnFe2O4 NHS is found to be most suitable for high-frequency applications as an efficient low-cost microwave absorber.

An increasing demand in electric power consumption has clearly led to an exhaustion of alternating energy resources. Undoubtedly, it has harmful environmental effects. Hybrid energy and Micro grid can solve this kind of problem. The concept of micro grid is quite significant in cases where transmission of electric power is nither feasible nor profitable. An efficient scheduling of micro grid is able to meet load demand without shedding any load and the optimization is required to make it profitable and eco-friendly. In this regard this work implements a twenty four hours based environmental/economic scheduling of distributed generating units with renewable energy sources in a micro grid connected with main grid .This work proposes a framework for optimal scheduling of micro grid which minimize the cost of generating units as well as emission. Particle Swarm Optimization technique has been employed to solve this problem. Weighting factor is used for optimization in multi-objective framework where both cost and emission are minimized simultaneously. In this paper, a comparative study of employing different types of Particle Swarm Optimization has been made where Hierarchical Particle Swarm Optimization (HPSO) performs better incorporating different constraints. The results of proposed Particle Swarm Optimization method are compared and verified with results of others method which is recently employed. Finally, the comparative study indicates that proposed method gives superior solution than previous method in case of operating cost and emission.

In the rapidly emerging field of multifunctional nanomaterials, this article highlights the surface functionalization of MnFe 2 O 4 nanoparticles (NPs) with tri sodiumcitrate dihydrate ligand and their efficacies in different application. The systematic spectroscopic analysis regarding UV-visible absorption and steady state fluorescence emission and excitation reveal that the citrate functionalized MnFe 2 O 4 (C-MnFe 2 O 4 ) NPs are capable of emerging multicolor fluorescence starting from blue, green to red. The magnetic measurements demonstrate that room temperature superparamagnetic nature of MnFe 2 O 4 NPs remains unaltered after surface modification. The potential of C-MnFe 2 O 4 nanoparticles for magnetic resonance imaging (MRI) is also unveiled in the perspective of the protein interaction. Moreover, these multifunctional C-MnFe 2 O 4 NPs exhibit excellent catalytic efficiency in the degradation of methylene blue, a water contaminant and bilirubin, a pigment responsible for jaundice.