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We report the studies of structure and properties of a quasi-one-dimensional (quasi-1D) compound ${\rm BaTiS}_{3}$ BaTiS 3 under pressure. The poly-crystalline samples are synthesized by solid-state reaction method and single-crystalline samples are produced by chemical vapor transport method. The XRD measurement under ambient pressure confirms the hexagonal structure, which consists of face-sharing octahedral ${\rm TiS}_{6}$ TiS 6 chains along c-axis and displays a quasi-1D feature. When applying pressure, the synchrotron X-ray diffraction experiments show that the sample undergoes a phase transition from hexagonal phase to orthorhombic phase at around 10 GPa due to the zig–zag deformation of ${\rm TiS}_{6}$ TiS 6 chains, while the quasi-1D structure is reserved. At ambient pressure, ${\rm BaTiS}_{3}$ BaTiS 3 exhibits an insulating behavior with a band gap about 0.273 eV. When applying pressure, the sample undergoes a crossover from insulator to metal due to the enhancement of inter-chain electron hopping. [ABSTRACT FROM AUTHOR]

Potassium sodium niobate (KNN) is an environmentally compatible piezoelectric material for substituting harmful lead-based ceramics. KNN-based ceramics have excellent piezoelectric properties with high Curie temperature. But, KNN faces difficulties during the processing like volatilization of alkali elements, chemical inhomogeneity, low densification, etc. The objective of this research is to investigate the impact of certain metal oxides additions like ZnO and MnO2 as sintering aids to solve the problems of the preparation and hence study the structural and electric properties of K0.5N0.5NbO3 (KNN) ceramics. ZnO and MnO2 added potassium sodium niobate, K0.5N0.5NbO3 was prepared by using the ceramic method. The prepared samples were sintered at 1000 °C for 2h conventionally. The structural properties of the ceramics have been analyzed by using X-Ray Diffractometer. The study demonstrates the formation of the orthorhombic-symmetric perovskite phase in all the prepared samples. The microstructural behavior of the ceramics has been characterized by techniques such as scanning electron microscopy (SEM) and compositional properties were studied by energy dispersive x-ray (EDAX). The effects of metal oxide additions on the electronic properties such as dielectric constant, dielectric loss, impedance properties, Nyquist plot, etc., were studied. The results have been analyzed and discussed in the paper. [ABSTRACT FROM AUTHOR]

A polycrystalline ceramic oxide, BaFe2MnO6 was produced through a regular solid-state route. The phase creation in the synthesized substance was investigated through X-ray diffraction (XRD) technique. The present material has found with made up of a single phase orthorhombic structure. The electrical properties of the compound were recorded through an LCR meter for a broader range of frequencies and temperatures. This perovskite oxide material possesses a large relative permittivity (ɛr = 1139) and low dielectric loss (tanδ = 0.421) at the ambient atmospheric condition, while the curie temperature arise beyond 450 °C. The resultant dielectric properties of this material assure its promising candidature for feasible applications in smart electronic devices such as dielectric material in ceramic capacitors. [ABSTRACT FROM AUTHOR]

I discuss the TPHP soil moisture content and temperature measuring digital system using Indium doped Tin Oxide nanopowder (ITO) electric heater and Nickel manganite (NiMn2O4) nanoceramic powder thermistor as a temperature sensor fabrication, characterization, calibration, and testing. The NiMn2O4 nanoceramic powder is synthesized using the wet chemical method and the ITO nanopowder-based heater is fabricated by a simple fill and press method. The heater, temperature sensor, Atmega328 microcontroller with its software, stainless steel cylindrical tubes, and 3D-printed package are used to fabricate the device. The distance between the heater and the temperature sensor is set to 0.006 m and heat pulse duration is set to 240 s. The heater consumes 3.587W electric power. The temperature sensor can measure the soil temperature up to 50°C. The system is capable of measuring volumetric soil moisture content from 3% to 37% efficiently with a strong correlation coefficient of $ 0.997 $ 0.997 with respect to the standard. The test result shows that there is less than a 2.8% error which is the smallest among the category and the sensitivity of the sensor at volumetric soil moisture content $ ({{\theta_v}})= 0.28{\textrm{m}^3}{\textrm{m}^{ - 3}} $ ( θ v ) = 0.28 m 3 m − 3 becomes $ 3.14^\circ \textrm{C} $ 3.14 ∘ C per $ {\textrm{m}^3}{\textrm{m}^{ - 3}} $ m 3 m − 3 . The developed system is simple to fabricate and operate highly precise, low cost, low power and light in weight. [ABSTRACT FROM AUTHOR]

In this paper, we studied the magnetism of Fe2N, using the ab initio and Monte Carlo studies. The magnetic moment and the exchange couplings are deduced by ab initio calculations. The obtained density of states is not symmetrical with respect to the axis of energy proving the ferromagnetic character of this compound. Any gap energy, at the Fermi level, is found confirming the metallic character of this compound. The Hamiltonian of this system consists of several physical parameters. Both the magnetic entropy and the maximum magnetic entropy are obtained. The relative cooling power and the magnetic hysteresis cycle are illustrated. The transition temperature TC value has been deduced and found to be about 252.01 K. This value is in good agreement with the experimental results presented. Also, we found that the magnetizations decrease rapidly to zero with increasing temperature. This is due to the ferromagnetic-paramagnetic phase transition caused by thermal energy. [ABSTRACT FROM AUTHOR]

Spinel ferrites are magnetic oxide materials with potentials to promote green technology in magnetic refrigeration which is known to be economically clean, energy saving and efficient. Maximum magnetic entropy change of spinel ferrites decides and controls the applicability as well as the strength of spinel ferrite magnetic oxide since it measures the hugeness of magnetocaloric effect. However, experimental determination of maximum magnetic entropy change requires intensive procedures, costly equipment and consumes appreciable time. Intelligent models are presented in this work using spinel-ferrite-molecular-based descriptors such as the ionic radii of spinel ferrites constituents, applied magnetic field and their concentrations. The developed intelligent models for prediction of spinel ferrite maximum magnetic entropy change include extreme learning machine (ELM) and hybrid genetic-algorithm-coupled support vector regression (GSVR). The developed ELM model has correlation coefficient (CC) and mean absolute error (MAE) of 98.45% and 0.117 J/kg/K, respectively, while the developed GSVR model has CC of 80.87% and MAE of 0.129 J/kg/J. The developed ELM model which is based on empirical risk minimization principle shows better performance over GSVR model that premises on structural minimization risk principle with improvement of 0.06%, 17.86% and 8.765% using root mean square error, CC and MAE yardsticks, respectively. Closeness of the estimates of the developed models with the experimental values is a strong indication of the potentials of the proposed intelligent methods in facilitating practical implementation of magnetic cooling refrigeration to solve energy crisis which promote efficiency and environmental friendliness. [ABSTRACT FROM AUTHOR]

The article presents the impedance analysis of polypyrrole (PPy)/La0.7Ba0.3MnO3 (LBM) nanocomposites synthesized by in situ chemical oxidation method. The morphology and crystal structure were analyzed by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. Vibration modes were analyzed using Fourier Transform Infrared spectroscopy (FTIR). The impedance behavior of the compounds was studied using an impedance analyzer in the frequency (100 Hz − 5 MHz) and temperature (30 °C − 90 °C) variation mode. Results of SEM and TEM for PPy, LBM, and PPy-LBM nanocomposites show spherical, rhombic and granular structures respectively. FTIR shows the presence of respective elements to be present for the formation of PPy, LBM, and PPy-LBM compounds. XRD patterns of PPy, LBM, and PPy-LBM nanocomposites show amorphous, orthorhombic, and semicrystalline phases respectively. The Real part of impedance shows decreasing value with frequency and the imaginary part of impedance shows the relaxing nature of the compounds. Cole − Cole analysis reveals the resistance contribution from grains and grain boundary. The equivalent circuit elucidated gives the combination of resistor and capacitor being parallel along with constant phase element and Warburg effects. The study helps us to understand the electric behavior of the samples whether capacitive or resistive type for which further studies can be conducted for sensor, anticorrosion coating, and spintronic applications. [ABSTRACT FROM AUTHOR]

Spinel ferrite recently attracted attention for possible application in magnetic refrigeration due to its noticeable high magnetocaloric effect and tunable magnetic ordering temperature around room temperature. Being a magnetic semiconductor, the material has enjoyed wider application in different practical domains such as drug delivery, humidity sensor, photo-catalyst, high density data storage, magnetic resonance imaging and magnetic cooling among others. However, simplicity of its preparation and excellent cost effectiveness as compared to the existing magnetocaloric-based materials further contribute to its suitability for attaining magnetic cooling. Effective utilization of this material for magnetic cooling requires precise measurement of its magnetic ordering temperature (MOT) which requires laborious experimental procedures and sophisticated equipment. This work addresses the challenges by employing elemental compositions of spine ferrite in developing hybrid models for predicting MOT using hybrid genetic-based support vector regression algorithm (GBSVRA) and extreme learning machine (ELM). The developed ELM-SN model with sine activation function performs better than hybrid GBSVRA and ELM-SG (with sigmoid activation function) model with performance improvement of 42.63% and 38.78%, respectively, through RMSE performance yardstick, while the ELM-SG model outperforms hybrid GBSVRA model with performance enhancement of 2.87% when validated using testing dataset. The developed ELM-SN model further outperforms other two developed models using other performance metrics. Harnessing the potentials of the presented models would strengthen precise, effective and quick tuning of spinel ferrite MOT for achieving magnetic cooling without experimental cost and difficulties. [ABSTRACT FROM AUTHOR]

The present paper reports on the effects of Aluminum-doping on the micro-structural and dielectric properties of La0.7Sr0.25Na0.05Mn0.95Al0.05O3 ceramics. The analyses of the X-ray diffraction data by the Rietveld refinement technique confirmed the formation of a rhombohedral phase in the R 3 ¯ c space group. The dielectric properties were analyzed by the complex impedance spectroscopic techniques in a wide temperature extent and a spectral range between 2 kHz and 1 MHz. The Nyquist diagram with a single semicircular arc is explained by the contribution of two conducting phases associated with the effects of grains and grain boundaries. The conductivity spectrum obeyed Jonscher's power law and the conduction mechanism was attributed to the correlated barrier hopping mechanism. The dielectric parameters such as the dielectric constant (ε″) showed a compositional dependence, indicating the prevalence of inter-grain conductive contribution and microstructural features which can be interpreted by the Maxwell–Wagner process. [ABSTRACT FROM AUTHOR]

The influence of the synthesis method on structural, magnetic and magnetocaloric properties of the La0.5Ca0.5Mn0.95V0.05O3 compound has been investigated. The compound was prepared by glycine nitrate process (GNP) and compared to counterparts obtained with solid-state route (S-S) and ball milling (B-M). The structural analysis shows a pure and single-orthorhombic crystalline phase for the GNP compound. A secondary phase LaVO4 was detected for S-S and B-M samples. From magnetization versus temperature analysis, different magnetic behaviors were distinguished when moving from one technique to another. The nature of transition was determined and a crossover from second order to first-order magnetic transition was observed with the decrease of crystallite size. Landau theory was performed to confirm the order of magnetic transition of the sample consistent with the Banerjee criterion. The magnetic entropy change (ΔSm) and the relative cooling power RCP, which decreased by reducing the particle size, were calculated. [ABSTRACT FROM AUTHOR]

We report first-principles calculations on the electronic, magnetic, and magnetocaloric properties of the perovskite metal compound Mn3GeC. We have studied this compound using a combination of density functional theory calculations (DFT) and Monte Carlo methods. The metallic perovskite Mn3GeC materials have a secondary ferromagnetic-paramagnetic transition around TC = 330 K. Our calculations show that this compound is more stable in the equilibrium state of the ferromagnetic network, estimated in agreement with the experimental parameter. The results of the simulation reveal that the Mn3GeC structure behaving of metallic nature; using calculations of first-principles, the magnetic and magnetocaloric properties have been calculated. Additionally, the magnetization and the susceptibility have been determined and the obtained critical temperature TC is in good agreement with the experimental results. The magnetic entropy and the relative cooling power for different external magnetic fields are obtained around TC. [ABSTRACT FROM AUTHOR]

This study evaluated metal availability under acidic soil conditions and identified the solid phases that govern their solubility using Baker soil test. Free metal ion activity (Mn+) expressed as negative logarithm value (pMn+ = -log10 Mn+) of iron (pFe3+), manganese (pMn2+), copper (pCu2+), zinc (pZn2+), nickel (pNi2+), cadmium (pCd2+), and lead (pPb2+) ranged from 17.5 to 21.3, 5.2 to 8.4, 12.2 to 15.3, 9.3 to 11.9, 11.5 to 14.8, 11.8 to 15.1, and 10.9 to 13.4, respectively. The activities of Fe, Cu, Zn, Ni, Cd, and Pb in the soil solution are likely to be buffered by exchange reactions rather than precipitation-dissolution reactions. However, bixybite and manganite oxides are likely to govern the free Mn2+ activity in the soils. Based on intensity and quantity parameters, the soils were found to have sufficient supply power for plant essential elements (i.e. Fe, Mn, Cu, Zn, and Ni) except in the coarse-textured soils of Kosi. Nevertheless, the toxicity of iron in Someshwar and cadmium in Dhaili soils is expected under the prevailing soil conditions. The generated information on the solubility vis-à-vis availability of metals under acidic soil conditions will contribute to enlarge a field of research which is crucial for land management and deserves more attention, particularly in the fragile mountainous ecosystem. [ABSTRACT FROM AUTHOR]

La0.4Pr0.25Ca0.35-xAgxMnO3 samples were elaborated using sol–gel method. X-ray diffraction study indicates that the investigated compounds exhibit an orthorhombic structure with Pbnm space-group symmetry. Introducing Ag in the investigated system leads to changes in the unit cell parameters and cell volume. The electrical properties have been investigated using the impedance spectroscopy technique. Dc-electrical resistivity study shows a metal-semiconductor transition at TMS = 220 K, which is Ag independent. Also, it is found that the resistivity decreases with increasing silver content. Then, the activation energy of the hopping mechanism is reduced with increasing Ag concentration. For different silver concentration, the conduction is dominated by thermally activated small polaron hopping (SPH) process at the high temperature and by variable range hopping (VRH) process at lower temperatures. [ABSTRACT FROM AUTHOR]

Ozone (O3) is a strong oxidant, which is able to oxidize carbonaceous solid soot even at ambient temperature. In this study, we found that the ozone-induced oxidation of soot was noticeably enhanced in the range 100–150 °C when La1-xKxMnO3 (x = 0, 0.1, 0.25) was used as a catalyst. The oxidation was limited at T < 300 °C owing to the thermal instability of ozone, but during temperature-programmed oxidation of soot from 25 to 700 °C, more than 70% of the carbon was combusted at T < 300 °C. The O3-induced soot oxidation rate over LaMnO3 at 150 °C was comparable to the NO2 (and O2)-induced soot oxidation rates over LaMnO3 at 430 °C and Pt/γ-Al2O3 at 410 °C. The K-substitution degree (x) of La1-xKxMnO3 had little influence on the catalytic activity in ozone-induced soot oxidation, which is a reflection of the similarity of the substituted catalysts in the number of surface oxygen vacancies. [ABSTRACT FROM AUTHOR]

Toward the development of infrared (IR) detectors, nickel–manganite-based thin films were initially prepared from (Ni0.2Mn2.8–xCux)Cl2 (0.010 ≤ x ≤ 0.040) solutions using the liquid flow deposition (LFD) method. The influence of Cu on the negative temperature coefficient of resistance (NTCR) characteristic of the films annealed at 400°C was investigated. It was found that the incorporation of Cu can effectively enhance electrical conductivity; however, it degrades both the thermal sensitivity and stability of the nickel–manganite films. The investigation was extended by further modifying the composition with Zn. The results revealed that by co-doping Cu with a proper amount of Zn the temperature coefficient of resistance (TCR) could be tailored, while a relatively low resistivity (ρ) of the final products was retained. Specially, when 0.01 mol Zn was added to a precursor solution containing 0.025 mol Cu, the resulting specimen possessed a TCR = 2.82% K–1 and a ρ = 820 Ω (measured at RT). More importantly, compared to Zn-free films, the (Zn,Cu) co-doped compositions showed much improved electrical stability, with an aging coefficient (ΔR/R) as low as 4.6%, after aging at 150°C in air for 500 h. The results suggest that the (Zn,Cu) co–doped (Ni,Mn)3O4 thin films have a promising application in IR detectors. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Bi substituted YMnO3 belonging to the series Y1-xBixMnO3 (x = 0, 0.3 and 0.5) were synthesised by employing a citrate gel method. X-ray diffraction confirmed the formation of a dominant phase of YMnO3 and scanning electron microscopy revealed grain growth. Temperature-dependent dielectric studies showed an increase in the dielectric response with temperature and also a change in the conduction mechanism with an increase in Bi percentage. The loss peaks obtained for Y0.5Bi0.5MnO3 samples indicate the existence of multiple relaxations. A cross over from polar hopping to a dipolar response is noticed which is a marked change in the conduction process. The Cole-Cole data also support such a phenomenon. Incorporation of Bi in YMnO3, a room temperature ferroelectric, transforms to a predominant orthorhombic structure aiding pronounced changes in the conduction process. [ABSTRACT FROM AUTHOR]

The paper investigates the magnetobarocaloric effect in a multiferroic composite made of ferroelectric and manganite components. Such a phenomenon can be classified as a secondary multicaloric effect. Its theoretical description is provided. In the presence of a magnetic field a temperature-dependent elastic field arises in the magnetostrictive material that results in the magnetobarocaloric effect. The effect reaches its maximum entropy change of 0.044 J kg−1K–1 at 312.5 K for the composite under study. [ABSTRACT FROM AUTHOR]

We report the synthesis of barium cerium manganite (BaMn0.94Ce0.06O3) single perovskite by using a conventional high-temperature solid-state reaction method. A structural phase transition occurs from hexagonal to orthorhombic confirmed by XRD data analysis after doping cerium (Ce) to the pure barium manganite (BaMnO3) matrix. The average crystallite size of the sample is about 63.38 nm. The lattice strain produced due to the addition of Ce dopant in the host matrix is about 0.00142. The SEM micrograph suggests the average grain size is about 30 μm. It is observed that the grain plays a dominant role compare to grain boundaries in defining the conductivity in the sample. The thermally activated relaxation process is controlled by the immobile charge carriers in the host materials at low-temperature range while controlled by defects at higher temperatures. From all the results, it is confirmed that the sample is dominated by the hopping process. The semicircular Nyquist plots confirm the semiconducting nature of the sample which is well supported by Cole-Cole plots. [ABSTRACT FROM AUTHOR]

In this article, we report the results of the Rietveld and impedance analysis of Eu doped La1–xEuxMnO3 (LEMO; x = 0.10, 0.30, and 0.50) perovskite manganites synthesized by solid-state reaction method. Structural studies through Rietveld analysis confirm that a mixed-phase nature of all LEM samples having a hexagonal unit cell structure with a less detectable impurity (Eu2O3) ceramics. The patterns are zanalyzed in detail with structural distortion and strain in LEM manganites ceramics. Dielectric constant and modulus are found to increase with increasing Eu concentration. The samples LEM-0.10 shows the negative capacitance at low frequency and temperature, respectively. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic properties and magnetocaloric effect (MCE) of NdCo2-xMnx (x = 0.0–0.5) compounds have been investigated. X-ray diffraction (XRD) analysis has revealed that all the compounds crystallize in the MgCu2-type cubic Laves phase structure (C15-type, Fd-3m). The lattice parameter a increases from 7.2987 Ǻ (x = 0.0) to 7.4020 Ǻ (x = 0.5) and the Curie temperature from 102 to 202 K as the Mn content increases to x = 0.5. Under an external field change from 0 to 5 T, a maximum magnetic entropy changes (ΔSM) value of 8.75 J/kg K was obtained for NdCo2. With an increase of Mn content, the calculated ΔSM shows an obvious decrease with a broader peak. However, the relative refrigerating capacities (RCP) of the NdCo2–xMnx compounds are larger than the parent compound. The Arrott curves and universal curves of the rescaled ΔSM confirmed that the NdCo2–xMnx compounds undergo a second-order phase transition. [ABSTRACT FROM AUTHOR]

First magnetic characterization of a recently developed generation of carbide free bainitic steels, known as Nanobain, has been performed. Stability of its retained austenite at cryogenic temperatures has been studied by means of X-ray diffraction, microscopy, dilatometry and magnetic measurements. Two morphologies for this phase (blocky-type and film-type) appear in a different proportion depending on the chemical composition and the applied thermal treatment. Inhibition of the martensitic transformation, when decreasing the temperature down to −271°C, has been observed in those microstructures with higher proportion of film-type austenite. The paramagnetic state of austenite at room temperature seems to lead to different magnetic behaviors (ferromagnetic, antiferromagnetic) at cryogenic temperatures (TC or TN being around −23°C in all the studied samples), depending on the proportion of such morphological features. Furthermore, irreversibility with temperature on the evolution of such magnetic behaviors has been observed for all the studied bainitic structures and is proposed to be due to a magnetic proximity effect. [ABSTRACT FROM AUTHOR]

Here the conglomerate bed consists of subparallel lenticular paleostream channels that contain copper-bearing ore shoots called the Calumet (or Main) ore shoot and the Lateral ore shoot. However, the conglomerate that contains vugs of manganite microcrystals shows little copper mineralization. The third locality where manganite microcrystals were found was the South Hecla mine on the southern end of the Calumet ore shoot in Calumet, Houghton County. [Extracted from the article]

In this work, the magnetic and transport properties of micro and nanometer-sized samples of La0.9Ba0.1MnO3 manganite have been studied. The temperature variation of ac susceptibility of the nanometer-sized sample shows one transition at high temperature (265 K). On the contrary, the ac susceptibility of the micrometer-sized sample shows two transitions with a high-temperature transition occurring at 240 K and low-temperature transition around 100 K. The high-temperature transition corresponds to the paramagnetic-ferromagnetic (PM–FM) transition (Tc) and is independent of frequency, while the low-temperature transition is frequency-dependent and shifts toward high temperatures by increasing frequency. The different magnetic behavior for two samples may be understood on the basis of crystalline homogeneity. The competition between FM double exchange and antiferromagnetic superexchange component in the micrometer-sized sample leads to the cluster glass state at low temperatures. The magnetotransport data further supports the obtained results from magnetic measurements. [ABSTRACT FROM AUTHOR]

La0.7Ca0.3MnO3 perovskite and its composites with graphene nanoplatelet (GNP) were prepared using a wet chemical method. The structural, magnetic and magnetocaloric properties of La0.7Ca0.3MnO3: GNP composites were investigated to determine the effect of GNPs. The results of XRD analysis show that the synthesised powders can be almost indexed to pure phase orthorhombic La0.7Ca0.3MnO3. The magnetic measurements demonstrate that 0.7 and 1% GNP amounts cause an increase in the Curie temperature (TC), and for larger amounts of GNP, the TC monotonically decreases, except for the sample with 10% GNP. The results obtained from the Arrott plots show that the magnetic phase transition of the samples transforms from the first to second order with increasing GNP amount. The changes in the magnetocaloric properties are interpreted in terms of perovskite phase formations via structural analysis. The amounts of graphene nanoplatelets in the oxide powders are correlated with the observed magnetocaloric properties. The best magnetocaloric performance with the maximum magnetic entropy change of 3.99 Jkg−1K−1 and refrigeration capacity of 90 Jkg−1 was obtained at a 2 T magnetic field. [ABSTRACT FROM AUTHOR]

Lithium ferrites-yttrium manganite composites were prepared by adding varying amount of yttrium manganite to lithium ferrite. The composites prepared have the general formula Li0.5Fe2.5O4+(x) YMnO3where x=(0, 10, 15, 20, 25, 30)wt%. They were studied for their structural properties by using X-Ray Diffraction (XRD) Technique. The XRD patterns revealed that in addition to the reflection peaks corresponding to cubic spinel structure of the ferrite components, few peaks which are reflections from planes of hexagonal yttrium manganite have been observed confirming the formation of composites. From the XRD data various structural parameters were evaluated and it is found that lattice constant and density increased slightly with addition of yttrium manganite while the crystallite size is decreased. The initial permeability and permeability loss of the samples showed resonance in the range 20-40MHz. The magnetic hysteresis properties were obtained from M-H loop measurements and it is found that the hysteresis parameters such as remanence and coercivity of lithium ferrites were improved with yttrium manganite additions. The results and the mechanism pertaining to the results have been discussed in the paper. [ABSTRACT FROM AUTHOR]

Yttrium manganite (YMnO3) and Chromium doped yttrium manganite (YMn1-xCrxO3) ceramic samples were prepared by sol-gel auto-combustion method. The as-prepared samples were annealed at 900 °C and sintered using conventional and microwave techniques. The influence of sintering technique on the structural and electrical properties was studied. The detailed structural investigations were carried out using X-ray Diffraction (XRD) and Fourier Transform Infra-red Spectroscopy (FTIR) studies. The variation of room temperature dielectric constant, dielectric loss and ac conductivity were studied as a function of frequency in the range 100 Hz–1 MHz using Agilent HP 4284A LCR(Inductance, Capacitance and Resistance) metre. [ABSTRACT FROM AUTHOR]

Yttrium manganite (YMnO3) and Chromium doped yttrium manganite (YMn1-xCrxO3) ceramic samples were prepared by sol-gel auto-combustion method. The as-prepared samples were annealed at 900 °C and sintered using conventional and microwave techniques. The influence of sintering technique on the structural and electrical properties was studied. The detailed structural investigations were carried out using X-ray Diffraction (XRD) and Fourier Transform Infra-red Spectroscopy (FTIR) studies. The variation of room temperature dielectric constant, dielectric loss and ac conductivity were studied as a function of frequency in the range 100 Hz–1 MHz using Agilent HP 4284A LCR(Inductance, Capacitance and Resistance) metre. [ABSTRACT FROM AUTHOR]

When La in perovskite (ABO3) manganite is partially substituted by rare earth element Er, average ionic radius on A site decreases, resulting in influence of internal pressure generated in a lattice on electronic activity energy band overlapped between the d orbit on B site and the p orbit on O site. Manganite polycrystalline samples La0.7-xErxCa0.3MnO3(x = 0, 0.1, 0.2) were prepared by solid-state reaction technique. X-ray diffraction spectra, resistance-temperature (R-T) curves and magnetoresistance-temperature (MR-T) curves of the samples were measured. The influence of different substitution of Er for La on low field magnetoresistance effect of the samples was analyzed. Experimental results showed that crystal structure of the samples was cubic structure. Lattice constant dMn-Mn, and transition temperature between ferromagnetic state and paramagnetic state TC of the samples decreased with the increase of Er doping. Tolerance factor t of the samples was less than 1 and Mn-O-Mn bond angle of the samples was less than The samples showed obvious low field magnetoresistance effect in experimental temperature range in 0.25 T magnetic field. [ABSTRACT FROM AUTHOR]

When La in perovskite (ABO3) manganite is partially substituted by rare earth element Er, average ionic radius on A site decreases, resulting in influence of internal pressure generated in a lattice on electronic activity energy band overlapped between the d orbit on B site and the p orbit on O site. Manganite polycrystalline samples La0.7-xErxCa0.3MnO3(x = 0, 0.1, 0.2) were prepared by solid-state reaction technique. X-ray diffraction spectra, resistance-temperature (R-T) curves and magnetoresistance-temperature (MR-T) curves of the samples were measured. The influence of different substitution of Er for La on low field magnetoresistance effect of the samples was analyzed. Experimental results showed that crystal structure of the samples was cubic structure. Lattice constant dMn-Mn, and transition temperature between ferromagnetic state and paramagnetic state TC of the samples decreased with the increase of Er doping. Tolerance factor t of the samples was less than 1 and Mn-O-Mn bond angle of the samples was less than The samples showed obvious low field magnetoresistance effect in experimental temperature range in 0.25 T magnetic field. [ABSTRACT FROM AUTHOR]

La0.8Ca0.2MnO3 manganese oxides have been prepared by the conventional solid-state reaction. The samples crystallize in the orthorhombic structure with Pnma space group. A first-order magnetic phase transition from ferromagnetic to paramagnetic state is observed at the Curie temperature that is found to be around 241 K. The magnetic and magnetocaloric properties have been simulated using a phenomenological model. The maximum of magnetic entropy change is of order 8.2 J/kg K for an applied magnetic field of 5 T, and the adiabatic temperature change is found to be of 4 K under a same magnetic field; this high value gives the sample the possibility of technologic application in the magnetic refrigeration area. The simulated results of magnetization and magnetic entropy change are compared with the experimental measurements. Finely, we found a good agreement between experimental and theoretical results. [ABSTRACT FROM AUTHOR]

La0.8Ca0.2MnO3 manganese oxides have been prepared by the conventional solid-state reaction. The samples crystallize in the orthorhombic structure with Pnma space group. A first-order magnetic phase transition from ferromagnetic to paramagnetic state is observed at the Curie temperature that is found to be around 241 K. The magnetic and magnetocaloric properties have been simulated using a phenomenological model. The maximum of magnetic entropy change is of order 8.2 J/kg K for an applied magnetic field of 5 T, and the adiabatic temperature change is found to be of 4 K under a same magnetic field; this high value gives the sample the possibility of technologic application in the magnetic refrigeration area. The simulated results of magnetization and magnetic entropy change are compared with the experimental measurements. Finely, we found a good agreement between experimental and theoretical results. [ABSTRACT FROM AUTHOR]

The present paper is focused on the study of different physical properties, especially magnetoimpedance (MI) of (x = 0-0.33) manganites of the rhombohedral structure. From the results of transmission electron microscopy it is evident that the average grain size lies in the range of 35-50 nm. MI measurements were carried out at room temperature for the frequency range of in presence of dc magnetic field of . The experimental results show that MI increases with the increase in grain size; the maximum MI () and a large ac MR () have been obtained for the sample under a field of at a frequency of . However, the same sample shows very low dc MR () under the same field. The MI results can be explained well in the light of skin depth effect and variation of transverse permeability with frequency. [ABSTRACT FROM AUTHOR]

Single phase Bi2Fe4O9 (Mullite BFO) nanoparticles were prepared first time by combustion method without using any solvent. Metal nitrates as oxidants and citric acid as fuel was used to synthesize Bi2Fe4O9 which were subsequently annealed at temperatures 550 °C, 600 °C and 650 °C. The impact of annealing temperature on crystal structure and physical properties are investigated by using X -ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electron Dispersion Spectroscopy (EDS), Ultra Violet Visible (UV–vis) spectroscopic studies and Fourier Transformed Infrared Spectroscopy (FTIR). X-ray diffraction confirmed orthorhombic phase of the Mullite BFO and peak profile analysis has been carried out to study the crystallite development in Mullite BFO nanoparticles. The Mullite BFO annealed at 600 °C showed minimum lattice strain. Further, the FTIR and UV-Vis spectra of the samples at room temperature confirm the formation of orthorhombic structure of the samples. Our results revealed that the band gap of Mullite BFO nanoparticles reduces with increase in strain and lowest band gap attained for strained mullite BFO annealed at 650 °C is 2.0 eV. The correlation of annealing temperature with calculated lattice and structural parameter of Mullite BFO nanoparticles was established. Magnetic measurements were carried out at room temperature up to a field of 30 kOe. All samples of Mullite BFO showed weak ferromagnetic behavior. Magnetic hysteresis loops showed a significant increase in magnetization for sample annealed at 600 °C. [ABSTRACT FROM AUTHOR]

The electrical resistivity was fitted with the phenomenological percolation model, which is based on the phase segregation of ferromagnetic metallic clusters and paramagnetic isolant regions. So, we found that the estimated results are in adequate accordance with experimental data. The relationship between electrical and magnetic properties of manganites has been traced through the analysis of temperature dependence of the La0.6Sr0.4Mn0.9V0.1O3 resistivity. The estimated critical exponents are (β = 0.326 ± 0.01; γ=1.237 ± 0.02 and α = 0.112). The values of these exponents obtained from resistivity are very close to them predicted by the 3D-Ising model. These results are in good agreement with the analysis of critical exponents from magnetization measurements. The obtained values of the temperature coefficient of resistance (TCR) for La0.6Sr0.4Mn0.9V0.1O3 sample is comparable with some systems used for infrared sensors. [ABSTRACT FROM AUTHOR]

Nanosized particles of La0.9Dy0.1MnO3 were prepared by sol-gel technique using citric acid as a chelating agent. The compound was analysed by powder X-ray diffraction technique and found to be single-phased orthorhombic in structure with space group Pnma which was confirmed with standard JCPDS data. The structural and morphological characterisations of synthesised material were carried out using XRD, Fourier transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectrometer. The magnetic study at room temperature shows the paramagnetic behaviour of the material. The existence of space charge polarisation and relaxation is due to the presence of oxygen vacancy illustrated from the real and imaginary part of impedance, respectively. The activation energy of synthesised material is calculated using Arrhenius equation from the impedance spectroscopy which corresponds to the existence of oxygen vacancy. [ABSTRACT FROM AUTHOR]

We have investigated the effects of barium deficiency on structural, magnetic and magnetocaloric properties of La0.6Nd0.1Ba0.3−xMn0.9Cr0.1O3(x= 0, 0.05 and 0.1) manganites prepared using the solid-state reaction. All the studied samples crystallize in the orthorhombic structure phase withPnmaspace group. Magnetization versus temperature showed that the samples exhibit a second-order paramagnetic to ferromagnetic transition with a decrease of the Curie temperature (TC) from 275 K forx= 0–235 K forx= 0.1. The increase of barium deficiency leads to the decrease of the maximum magnetic entropy changeand relative cooling power values from (4.40 J.kg−1K−1and 262.94 J.kg−1, forx= 0) to (2.78 J.kg−1K−1and 159.41 J.kg−1, forx= 0.1) for an applied magnetic fieldμ0H= 5 T. These values are compared favorably with those of some other reported manganites, making our samples promising candidates for the magnetic refrigeration technology. [ABSTRACT FROM AUTHOR]

We present the structural investigation on multiferroic Ba1-xSrxMnO3perovskite manganites with x = 0.50, 0.60, 0.70 and 0.75 synthesized by combustion method. Rietveld refinement of powder X-ray diffraction data reveals the hexagonal structure with space group P63/mmc for all compositions. The unit cell lattice parameters for Ba1-xSrxMnO3decrease monotonically with Sr-substitution on Ba-site. The value of structural tolerance factor decreases from 1.047 for x = 0.50 to 1.018 for x = 0.75. [ABSTRACT FROM PUBLISHER]

Effect of cation substitution on the structural, electrical and magnetic properties in an electron-doped perovskite manganites viz. La0.90Zr0.10MnO3(Zr10) and La0.90Te0.10MnO3(Te10) prepared by solid-state reaction is reported herein. XRD indicates that both samples are polycrystalline with rhombohedral crystal structure. The strong absorption in FTIR spectra at ∼615 cm−1was of Mn-O bond, which gets slightly shifted due to different ionic radii of cations. A large resistivity with a slight increase in transition temperature in the case of Te10 than Zr10 indicates that the ‘Te’ doping stabilizes the ground state of double-exchange mechanism between theeglevels andt2glevels. [ABSTRACT FROM AUTHOR]

Presently, the effect of divalent Ca ions on the structural and transport properties of YMnO3is studied. A series of (Y1-xCaxMnO3x = 0.00, 0.03, 0.05, 0.1, 0.25) samples were synthesized by solid state reaction method. X-ray diffraction shows that pure YMnO3have hexagonal while Ca doped compounds possess mixed (hexagonal and orthorhombic) phase for all concentrations of Ca. Ferroelectric behavior of all samples was also investigated by PE loop. Furthermore, dielectric constant is found to improve after Ca doping which is understood in terms of electronic phase separation that generally occurs in charge ordered manganites. [ABSTRACT FROM AUTHOR]

Polycrystalline yttrium iron manganites – YMn1-xFexO3(with x = 0.0, 0.1, 0.15, 0.20) were synthesized by ceramic method and sol-gel auto-combustion method. XRD confirmed the formation of hexagonal phase in all samples. The hexagonal a– and c- parameters for the samples prepared by the sol-gel method are found to be closer to the stoichiometric values. The room temperature frequency variation of electrical properties such as dielectric constant, dielectric loss and ac conductivity showed a dispersive behavior for all the samples. The values of dielectric constant and dielectric loss are found to be lower for the sol-gel prepared samples. [ABSTRACT FROM AUTHOR]

Sr-substituted perovskites, La1.8Sr0.2MMnO6(M = Ni, Co), were synthesized using the solid-state reaction technique to present a systematic study on their morphological, structural and magnetic properties. The average grain size of the as-prepared La1.8Sr0.2NiMnO6samples are in the range of 0.2–0.7µm and those for La1.8Sr0.2CoMnO6manganites are 0.1–2.8μm, which is significantly less than that of unsubstituted La2NiMnO6(LNMO) and La2CoMnO6(LCMO) manganites. The XPS analysis enlightened about phase purity, binding energy and oxygen vacancy of La1.8Sr0.2MMnO6manganites. The Sr-substituted LNMO has revealed a sharp ferromagnetic to paramagnetic phase transition at 160 ± 2 K, which is about 120 K less than that of parent LNMO. The Sr-substituted LCMO exhibited such a transition at 220 ± 2 K, which is 8 K less than that of parent LCMO. The temperature-dependent magnetization measurements suggest that the effect of Sr on the transition temperature in LNMO is more significant than that of LCMO. [ABSTRACT FROM AUTHOR]

In this paper, a table-like magnetocaloric effect (MCE) is obtained in the (AMn0.9Ti0.1O3)1−x/(AMn0.85Ti0.15O3)xcomposite system. A flattening behaviour of the entropy change is investigated from the isothermal magnetic entropy change versus temperature curves ∆S(T) of AMn0.9Ti0.1O3and AMn0.85Ti0.15O3(A = La0.57Nd0.1Pb0.33) manganite materials. Both compounds exhibit nearly some large MCE, 5.2–4.85 J kg−1K−1, under an applied field of 0–5 T, around their respective Curie temperature (TC) ranged from 279 to 299 K. The temperature dependence of the isothermal magnetic entropy change ΔS(T) is calculated for (AMn0.9Ti0.1O3)1−x/(AMn0.85Ti0.15O3)xcomposite with 0 ≤x≤ 1. The optimum ΔS(T) of the composite withx= 0.495 approaches a nearly constant value of ∼3.63 J kg−1K−1in a field change of 0–5 T in a wide temperature span over 15 K, resulting in large refrigerant capacity value of ∼172.3 J kg−1. The (AMn0.9Ti0.1O3)0.505/(AMn0.85Ti0.15O3)0.495composite system indicates that this approach can be used to design magnetic refrigerant materials with enhanced magnetocaloric response in a magnetic refrigerator performing an Ericsson cycle near room temperature. [ABSTRACT FROM AUTHOR]

The critical properties of perovskite manganite La0.67Ba0.33−xZnxMnO3around the paramagnetic–ferromagnetic phase transition are investigated through various techniques such as modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis. Through the nature of this transition was found to be in second order. The value of critical exponent, derived from the magnetic data using the Kouvel-Fisher method, yields,and 4.600.034.66 ± 0.06 with aTCof 259.98 ± 0.32 − 221.73 ± 0.05 K. The exponent values are close to those expected for three-dimensional Heisenberg ferromagnets with short-range magnetic interaction. [ABSTRACT FROM AUTHOR]

Local charged states have been induced at the surface of lanthanum strontium manganite single crystals as a result of the local bias application by a conducting tip of atomic force microscope. These results show the dependence of the surface potential of induced area on the writing time similar to that for ferroelectrics. Phenomenon of phase separation with charge segregation is considered for low-doped manganites. It indicates the tendency of manganites toward charge segregation stimulated by the magnetic ordering. [ABSTRACT FROM PUBLISHER]

The paper first introduces the basic physics behind perovskite multiferroics. Then the recent progress on simple, complex perovskites, and manganites are briefly reviewed. The review discloses two important directions on achievement multiferrocity in perovskite: pay with strain engineering and adjust octahedral deformation. The authors also suggest that specific issues like leakage current and characterization platforms are also very important for the study of multiferroics. [ABSTRACT FROM PUBLISHER]

In this paper, we present the drug loading and release works of(LSMO) manganite nanoparticles (NPs). The LSMO NPs, grown using the sol–gel method, were embedded in an acrylic interpenetrating polymer network to make the sample applicable for biomedical purposes. The results of scanning electron microscopy showed that these NPs were well dispersed in the polymer. The grain size of these NPs lies in the range of 25–45 nm, as confirmed by transmission electron microscopy. The measurements of DC magnetization and hysteresis loops reveal that the basic magnetic behaviour of the LSMO NPs remained almost unaltered even after embedding in polymer, but with lower saturation value of magnetization. The drug loading and release studies of the grown sample were carried out using an antibiotic, ciprofloxacin. The minimum inhibitory effect of the sample loaded with this drug has exhibited high activity against different strains of bacteria, comparable to the pure ciprofloxacin. [ABSTRACT FROM PUBLISHER]

Local charged states have been induced at the surface of lanthanum strontium manganite single crystals as result of the local bias application by a conducting atomic force microscope tip. The piezoelectric contrast is observed in these states pointing to the existence of a local polar state. The induced charged states relax with characteristic time constant of about 50–100 hours at room temperature. Charge and size of the created structures increase significantly if the induction occurs in a magnetic field. It indicates the tendency of manganites toward charge segregation stimulated by the magnetic ordering. [ABSTRACT FROM PUBLISHER]

In this article, the influences of grinding particle size on the structure and electrical transport properties of La0.67Sr0.33MnO3−δcompound have been investigated. The compound was prepared by gel combustion process followed by grinding for different duration time. It was found that the lattice parameters, unit-cell volume, strain, oxygen deficiency, and temperature dependence of resistivityρ–Tincrease with decreasing particle size. Theρ–Tgrowth can be explained by the increasing contribution of the grain boundary effect, strain, and even oxygen deficiency. The electrical transport mechanism over the whole temperature range of 100–400 K was thoroughly described by applying the phase separation model around the phase transition temperatureTP. This model was subsequently employed to calculate theρ–Tat high temperature up to 1000 K. The result showed there was a second phase transition at a typical temperatureT*>TP, which could be attributed to the relaxation of small polarons to large ones. This relaxation occurred at lower temperatures when the particle size decreased. It might be due to the decrease in conduction bandwidth caused by the defects arisen during the grinding. [ABSTRACT FROM AUTHOR]

A detailed structural, magnetic and physics properties of La1−xMnO3±δ(LMO) nanomanganites were investigated to find out the role of cationic vacancies (La vacancy with Mn3+/Mn4+) in grain size modulation. Crystal structure and phase analysis of all samples were carried out by Rietveld refinement of high-resolution XRD and neutron diffraction data. We report here, the oxygen content in studied LMO compound decreases with increase in La vacancies in parent site and a parasitic Mn3O4phase has been evolved in the range of 0.9 ≥ La/Mn ≥ 0.7. Para to ferro magnetic transition temperature (TC) of all nanometric samples (La/Mn < 0.9) was found at high temperature side (≥260 K) whereas, the same for bulk one (La/Mn ≥ 0.9) was around 160 K. The enhancement ofTC(~70 K) with size reduction is attributed to broadening of bandwidth due to compaction of MnO6octahedra in system unit cell. In bulk sample, a secondary cluster/spin glassy phase is found below 50 K, whereas the glassy phase has been suppressed in nanoscale. Field-dependent magneto-resistance measurements are also carried out for all samples at different temperatures to get a profound insight of magneto-transport dynamics of the present system. [ABSTRACT FROM AUTHOR]

The lattice contribution to the thermal conductivity (κph) of La0.95Ag0.05MnO3manganites is theoretically analysed within the framework of Kubo model. The theory is formulated when thermal conduction is limited by the scattering of phonons from defects, grain boundaries, charge carriers, spin waves and phonons. The lattice thermal conductivity dominates in Ag-doped manganites and is artefact of strong phonon–impurity and phonon–phonon scattering mechanism in the ferromagnetic metallic state. The electronic contribution to the thermal conductivity (κe) is estimated following the Wiedemann–Franz law. Another important contribution in the metallic phase should come from spin waves (κm). It is noticed that κmincreases with aT2dependence on the temperature. The behaviour of the thermal conductivity in manganites is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between electron, magnon and phonon contributions. [ABSTRACT FROM PUBLISHER]