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The effects of light illumination and magnetic field on the electrical transport properties of La0.67Ca0.33MnO3 thin film on a silicon substrate have been studied in detail. Large value of colossal magnetoresistance has been observed under an applied magnetic field in the whole temperature range below 150 K which is related to the presence of both antiferromagnetic and ferromagnetic phase in the sample. A significant amount of resistance drop is caused by light illumination even at extremely low light intensities, ∼−22% with light of 0.3 μ W cm−2 intensity and ∼−42% with 6.2 μ W cm−2 intensity at 600 nm wavelength. There has been a notable rise in the photoinduced magnetoresistance value, specifically, a significant decrease in resistance occurs in simultaneous presence of magnetic field and light. For 1 T applied magnetic field, MR% rises from −33% in dark to −58% under light illumination at 150 K i.e. ΔMR% is 25%. As the strength of the magnetic field increases, ΔMR% decreases, suggesting that the magnetoresistive photoinduced phenomenon is more pronounced in the presence of mix phases in the sample. This combined enhanced magnetoresistive photoinduced phenomenon is explained by the interaction of photogenerated charge carriers in the sample and applied magnetic field. [ABSTRACT FROM AUTHOR]

The present work provides a detailed investigation of the electronic- and magneto-transport properties of bulk and nanostructured Nd0.7-xGdxSr0.3MnO3 (x = 0, 0.1, 0.2 and 0.3) polycrystalline manganites. We have specially addressed the issue of the observed minimum in the temperature dependent resistivity of these manganites in the low temperature regime (<50 K). It is observed that increase of A-site disorder due to progressive substitution of Gd and decrease of grain size enhances the observed resistivity minima. Different theoretical models have been employed to analyze the resistivity data in the low temperature regime. It has been established that the quantum interference effect due to electron–electron interaction, most likely, is the dominant factor of the observed resistivity minimum and upturn in resistivity in the lower temperature regime. The effect of phase separation is also found to play a key role in the electronic-transport of the materials. Further the magnetoresistance is found to increase with the increase of Gd concentration as well as with the decrease of grain size in the low temperature regime. The origin of magnetoresistance has been critically analyzed. [ABSTRACT FROM AUTHOR]

In this work, we have studied the effect of annealing temperature (T S) on the structural properties and the critical behavior of Nd 0.5 Sr 0.5 MnO 3 compound prepared by sol-gel method (T S = 600, 700, 800 and 1000 °C). Scanning electronic microscope images indicate that all the samples are nanosized. The refinement of X-ray diffraction data shows that the samples sintered at 600 °C and 700 °C have three structural phases and that the monoclinic phase is linked to a superstructure (superlattice). The samples sintered at 800 °C and 1000 °C crystallize in the orthorhombic structure with Pnma space group, indicating the occurrence of a structural transition with increasing particle size. The magnetic measurements reveal that all our samples exhibit a paramagnetic to ferromagnetic transition with the absence of the long-range charge-ordered antiferromagnetic state. Through the magnetic field dependent magnetization, the observed overlapping between the isotherms suggests the persistence of some antiferromagnetic ordering in the nanosized samples. The reduction of saturation magnetization at 5 K for the sample sintered at 1000 °C indicates the beginning of the establishment of long-range charge ordering. The study of critical exponents has shown that the mean-field model is the most suitable model to describe the magnetic interactions for all our samples, suggesting the presence of long-range ferromagnetic interactions. [ABSTRACT FROM AUTHOR]

This study explores the critical behavior and magnetocaloric properties of La0.5Sm0.2Sr0.3Mn1-xCrxO3 manganites, with a focus on the novel effect of Cr doping (x = 0, 0.1, 0.15, and 0.2) on magnetic phase transitions and magnetocaloric response. Unlike previous works, this study provides new insights by revealing how chromium substitution alters the critical exponents γ and β, using modified Arrott plots (MAPs) and the Kouvel–Fisher method, resulting in a deviation from mean-field theory and suggesting a shift in the universality class. These findings underscore the novel impact of Cr on magnetic ion interactions and lattice structure. Furthermore, this research uniquely examines the effect of Cr doping on the magnetocaloric effect (MCE), showing that increasing Cr content tailors the magnetic entropy change − ∆SM(T) and the Temperature-Averaged Entropy Change (TEC), enhancing the potential of these materials for magnetic refrigeration. This work significantly contributes to the optimization of manganites for applications in magnetic cooling, spintronics, and temperature-sensitive sensors. [ABSTRACT FROM AUTHOR]

The current work discusses on the effect of sodium (Na) and bismuth (Bi) ion doping at different concentrations in the compositional formula La0.67Sr0.33–yNay/2Biy/2MnO3 (y = 0, 0.0825, 0.165, 0.2475, 0.33) on structural, magnetic, magnetotransport and thermoelectric studies. X-ray diffraction confirms the R c space group with rhombohedral structure and the field emission scanning electron microscope images confirms a systematic growth of grains with increasing in NaBi concentrations. An enhancement in the ferromagnetic ordering and magnetic transitions above 325 K were observed up to y = 0.165 and they decrease thereafter. A broad maximum along with a double peak behavior were noticed in the temperature dependent resistivity curves and they disappear upon the application of external magnetic fields. The Seebeck coefficient show a change of sign from positive to negative with increasing temperature for lower concentrations of NaBi and they exhibit a negative sign for higher substitutions suggesting the variation in the nature of charge carriers. The small polaron hopping mechanism governs the resistivity and thermopower behavior in the high temperature regions while, electron-electron, electron-magnon, magnon-magnon scattering mechanism contributes in the low temperature region. [ABSTRACT FROM AUTHOR]

Herein, the impact of exposing the perovskite compound Pr0.5Sr0.5MnO3 to oxygen plasma is explored by comparing the structural and transport properties of the exposed samples to those of the unexposed ones. The Pr is oxidized to PrO2 in the investigated samples due to plasma exposure. The alterations in the transport properties can be linked to the changes in MnOMn bond angle and MnO bond length due to plasma exposure, as indicated by X‐ray diffraction analysis. Additionally, exposure to oxygen plasma increases the conductivity by incorporating oxygen into the exposed samples, making them oxygen‐rich. Detailed analysis of the resistivity and thermoelectric power data indicates that small polarons are responsible for conduction at high temperatures, while at low temperatures, variable range polarons take over. The negative value of the thermopower at all temperatures proclaims that the electrons behave as the dominant charge carriers. [ABSTRACT FROM AUTHOR]

In this study, La0.63Sr0.2Nd0.17MnO3 was synthesized by the sol-gel method, and its structural, morphological, magnetic, and magnetocaloric effects were investigated. The structural properties were analyzed by x-ray diffraction (XRD), and scanning electron microscopy (SEM) was used to characterize the morphology. An integrated magnetic measurement system was used to determine the magnetic properties. La0.63Sr0.2Nd0.17MnO3 crystallized in a hexagonal crystal system with space group R-3c. This was also confirmed by Rietveld refinement of the x-ray data from La0.63Sr0.2Nd0.17MnO3. With the doping of Nd3+, the cell volume decreases, which can be explained by the angles and bond lengths of the bonds between the Mn and O ions and the distortion of the lattice. Near the Curie temperature, La0.63Sr0.2Nd0.17MnO3 exhibits significant magnetocaloric effects. The magnetic study of La0.63Sr0.2Nd0.17MnO3 suggests that the transition from the paramagnetic to ferromagnetic phase can occur near the Curie temperature. The maximum magnetic entropy change and relative cooling power (RCP) of La0.63Sr0.2Nd0.17MnO3 (298 K, 3 T) are 2.70 J/(kg K) and 135 (J/kg), respectively. The effect of f-orbitals on the magnetic properties of La0.8Sr0.2MnO3 was investigated by first-principles calculations in density functional theory. Thus, it can be concluded that the magnetocaloric effects of the material after doping with f-orbital ions (Nd3+) is enhanced compared to La0.8Sr0.2MnO3. [ABSTRACT FROM AUTHOR]

This study investigates the critical behavior analysis and predicting magnetocaloric properties of La0.6-xGdxSr0.4MnO3 manganites, focusing on the impact of varying gadolinium (Gd) doping levels (x = 0, 0.0125, 0.05, and 0.10). Using modified Arrott plots (MAPs) and the Kouvel–Fisher method, the critical exponents γ and β were determined, yielding values that indicate how Gd content influences magnetic phase transitions. Additionally, the magnetocaloric effect (MCE) was analyzed to assess the magnetic entropy change − Δ S M (T) and the Temperature-Averaged Entropy Change (TEC) across different magnetic field changes. The results show that increasing Gd doping enhances the magnetocaloric response, suggesting potential applications in magnetic refrigeration. Overall, the study provides insights into optimizing these manganites for applications in high-temperature sensors, spintronics, and magnetic cooling. Highlights: Using modified Arrott plots (MAPs) and the Kouvel–Fisher method, the critical exponents γ and β of La0.6-xGdxSr0.4MnO3 (x = 0, 0.0125, 0.05, and 0.10) manganites were derived. The magnetocaloric effect (MCE) was analyzed to assess the magnetic entropy change − Δ S M (T) and the Temperature-Averaged Entropy Change (TEC) across different magnetic field changes. [ABSTRACT FROM AUTHOR]

The crystal structure of La 0.7 Sr 0.3 Mn 1−x Al x O 3 (LSMAO) with x = 0,0.025,0.05,0.075 and 0.10 ceramics prepared by the Sol-gel method were investigated by employing the XRD technique. The XRD patterns analysis by employing the Rietveld analysis confirms the nonexistence of secondary crystal phase/s and, materials are crystallized to the R-3c(167) space group. The microstructural properties were studied using scanning electron microscope (SEM) and transmission electron microscope (TEM). The dielectric property, AC conductivity, complex impedance spectroscopy and complex electrical modulus have been studied over a wide range of frequencies (103 Hz–107 Hz) at different temperatures from 313K to 393K. The Non-Debye type relaxation process has been observed in synthesized samples confirmed from the Nyquist plot. The Cole-Cole plots were employed to estimate the individual grain and grain boundary contributions. The Maxwell-Wagner (MW) polarization model provides an explanation for the greater values of dielectric constant at the lower frequencies. The present study explores the technological usefulness of LSMAO. [ABSTRACT FROM AUTHOR]

This study examined the structural and magnetic properties of polycrystalline perovskite Pr0.47La0.20K0.33Mn0.91Cu0.09O3. Through Rietveld refinement of powder X-ray diffraction data, it was determined that the material possesses an orthorhombic structure with space group Pnma. At the Curie temperature ( T C = 177.80 K ), the magnetization behavior shifted from paramagnetic to ferromagnetic, revealing a Griffiths phase characterized by downward divergence from the Curie–Weiss law. Key parameters such as the Curie temperature TC, the Griffiths temperature ( T G ), and the Griffiths exponent (λ) were determined to be 177.80 K, 287.85 K, and 0.0762, respectively. To analyze the saturation magnetization data at higher magnetic fields using the law of approach to saturation (LAS) model, we can determine the magneto-crystalline anisotropy constant (K1). The value of (K1) was estimated to be approximately 1.27 × 106 erg/cm3 = 1.27 × 105 J/m3. These findings suggest that the Pr0.47La0.20K0.33Mn0.91Cu0.09O3 sample shows promise as a candidate for multifunctional devices. [ABSTRACT FROM AUTHOR]

The ferromagnetic La 1 - x Sr x MnO 3 (LSMO) manganites are ideal materials for magneto-caloric applications due to their high Curie temperature. Here, we prepare open-cell, porous LSMO foams starting from a commercial polyurethane (PU) foam and commercial LSMO powder with x = 0.3. The cut PU foams are then covered by a slurry of LSMO powder mixed with PVA and water, and then, the foams are subjected to a heat-treatment with two steps at 600 ∘ C (burn-off organic material) and 1200 ∘ C (sintering/compacting). The resulting ceramic LSMO foams are then characterized by X-ray, SEM, electron backscatter diffraction (EBSD) orientation mapping and magnetic measurements. The foam sample consists of randomly-oriented LSMO grains with an average grain size of 188 nm, being distinctly smaller than bulk samples of the same composition, but considerably larger than LSMO nanowires prepared by electrospinning. The magnetic data reveal a high Curie temperature like the bulk samples, and an entropy change, - Δ S M slightly higher than that of the bulk samples, which points to a strong influence of the LSMO grain size. Thus, the resulting LSMO foam material is well suited for magneto-caloric applications at room temperature. [ABSTRACT FROM AUTHOR]

The Sm0.47La0.20K0.33MnO3 perovskite manganite was synthesized using the solid-state reaction method and its structural, magnetic, and critical properties were investigated. This work analyzed the structural characteristics of our sample through Rietveld refinement of the X-ray diffraction pattern and Hirshfeld surface mapping (HS) techniques. It was shown that the sample crystallized in the space group Pnma, with the lattice parameters: a = 5.461 (4) Å, b = 5.478(1) Å, and c = 7.706(8) Å. The Mn–O bond length ~ 1.9 Å obtained from the Rietveld refinement, agrees with the minimum distances between Mn and O atoms obtained from the characteristic 2D fingerprint plots of this manganite. From M vs. T measurements in the range of 5 K < T < 300 K and isothermal measurements M (H) in the range of 0 T < H < 6.5 T , two phase transitions were observed: (i) a paramagnetic (PM)—ferromagnetic (FM) second-order phase transition, and (ii) a FM—spin-glass-like transition. The latter is associated with the presence of samarium in the crystalline structure of the manganite studied. Furthermore, a collective freezing state occurs at T B = 72.83 K . The behavior of the inverse of susceptibility χ - 1 (T) vs. T shows the coexistence of FM clusters within the PM state ( T > 184 K ). Modified Arrott plots (applied to 3D-Heisenberg, 3D-Ising, and Tricritical mean-field models), as well as the Kouvel-Fisher method, were employed to obtain the critical coefficients that were found to be β = 0.367 , γ = 1.330 , and δ = 4.776 for the Sm0.47La0.20K0.33MnO3 manganite. It was confirmed that both critical exponents (β and γ) satisfy the Widom scaling relation (δ = 1 + γ β) . However, a slight deviation from the theoretical values exists of the critical exponent δ obtained with the 3D Heisenberg model. This may be due to the nanoscale dimensions of the secondary phase KMn 2 O 6 particles. In conclusion, critical coefficients and observed phase transitions are significant because they provide guidance for theoretical modeling, enabling real-world applications in diverse technical domains, and shed light on material behavior, all of which contribute to our understanding of manganites. Based on the results of the search, it appears that a better understanding of the critical magnetic behavior in polycrystalline manganites may greatly improve future research and applications in the following areas: Hard disk drives HDDs and magnetic tapes are magnetic data storage devices which can benefit from manganite research to be advanced. Spintronics is a technology, which is based on electron spin polarization mechanism to process information. It utilizes manganites as an important material. [ABSTRACT FROM AUTHOR]

We have systematically investigated the critical behavior around paramagnetic-ferromagnetic (PM-FM) phase transition temperature, TC, and attempted to determine the Curie temperatures and critical exponents β, γ and δ of perovskite manganites La0.67Ba0.33–xSrxMnO3 (x = 0.1, 0.2 and 0.25).The TC determined from M(T) is observed to increase from 336.7 to 368.4 K, with Sr doping at Ba. The critical exponents β, γ and δ are determined from the magnetization, M(T,H), using Modified Arrott Plots for theoretically predicted models and critical M(H) isotherms at T = TC. From the critical exponents we have inferred that La0.67Ba0.33–xSrxMnO3 behave as a three-dimensional (3D) isotropic nearest heighbor Heisenberg ferromagnet in the critical region. We have further verified that the behavior of 3D isotropic nearest neighbor Heisenberg is in agreement with the values of exponent 'n' determined based on the relation between field dependent change in magnetic entropy at the Curie temperature, T = TC. Sr doping at Ba site in La0.67Ba0.33–xSrxMnO3 does not lead to any crossover in the type of magnetic interactions present in the materials, indicating a stable behavior of 3D isotropic nearest neighbor Heisenberg ferromagnet in the critical region. The differences in the values of parameters may be attributed to the complex nature of interactions present in these materials. [ABSTRACT FROM AUTHOR]

In this study, we have characterized the magnetic and magnetocaloric (MC) properties of composites formed by two manganites with appropriate Curie temperatures (TC) and acceptable maximum magnetic entropy change ( - Δ S M max ) values. The composites have similar diffraction patterns obtained for the main phases La0.67Ca0.27Sr0.06MnO3 (LCSM) and La0.7Sr0.3Mn0.95Cu0.05O3 (LSMC) overlapping the diffraction peaks of the perovskite structure. The absence of any diffraction peaks distinct from the main phases in the XRD patterns of the composites indicates that there is no third phase besides the main ones. It is understood from the SEM images that the composites are composed of particles of different shapes and that the interparticle spacing decreases and the grain boundaries become clear, indicating that the interaction between particles becomes stronger with the increase of the y ratio. A gradual transition is seen from the M(T) curves, which specify that the composites consist of phases with discrete transition temperatures. The magnetic phase transition of the samples is second order. The - Δ S M max value has been calculated as 3.18, 3.24, and 4.05 J kg−1 K−1 at 5 T magnetic field for the composites 0.25LCSM/0.75LSMC, 0.50LCSM/0.50LSMC, and 0.75LCSM/0.25LSMC, respectively. Since the RCP value of 0.5LCSM/0.5LSMC composite is 301.61 J kg−1 under 5 T, it can be considered as a promising candidate for use in various magnetic cooling technologies at room temperature. [ABSTRACT FROM AUTHOR]

Swift heavy ion (SHI) irradiated LaMnO 3 /La 0.7 Ca 0.3 MnO 3 (LMO/LCMO) interfaces have been investigated to understand their charge transport and conduction mechanisms. Prominent effect of ion fluence has been discussed for the interface resistivity behaviors and metal to insulator phase transition for LMO/LCMO interfaces on the bases of lattice strain, crystalline granular state, crystalline imperfection, average grain size, grain boundary density and rms surface roughness. Field effect configuration (FEC) has been employed to study the interesting modifications in the irradiated LMO/LCMO interface resistivity under different applied electric fields to understand the depletion region, free charge carrier density, ferromagnetic phase fractions and crystal field based distortions. A Phenomenological percolation model has been employed to understand the role of phase separation in governing the charge conduction processes across LMO/LCMO interfaces. [ABSTRACT FROM AUTHOR]

Charge transport studies on pulsed laser deposition grown Y0.95Ca0.05MnO3 (YCMO) thin film on (100) single crystalline Nb:SrTiO3 (SNTO) substrate. X-ray diffraction analysis reveals the single phase nature of YCMO manganite film having lattice mismatch between YCMO thin layer and SNTO substrate. Surface morphology, studied using atomic force microscopy, indicates the presence of island like grain growth with narrow size distribution. Transport properties have been studied by performing temperature dependent resistivity under different applied voltages across the YCMO/SNTO interface to understand the charge conduction across the same interface. The observed electric field-induced modifications in interface resistance across the YCMO/SNTO lattice have been discussed in the contexts of barrier between YCMO and SNTO, oxygen vacancies, structural disorder and structurally strained region at the film–substrate interface. Electrical resistance has been theoretically fitted using various models and mechanisms to better understand the charge conduction mechanisms in the semiconducting region for the YCMO/SNTO interface. [ABSTRACT FROM AUTHOR]

Doped calcium manganite perovskites CaMnO 3− δ which constitute some of the most promising materials for all-oxide thermoelectric generators for conversion of heat to electricity operating in air over a wide temperature range have been modified by Sr–Pb–Ho co-doping. The Ca 0.5 Sr 0.45− x Pb 0.05 Ho x MnO 3− δ samples (x = 0.05, 0.10, 0.15 and 0.20) synthesized by the citrate-nitrate method of precursor preparation are shown to have an orthorhombic crystal structure (space group Pbnm) at room temperature. The relationship between temperature, concentration of donor ions, Jahn-Teller distortions and energy parameters of carrier formation and mobility that affect the thermoelectric properties of electron-doped manganites has been studied. The temperature-activated nature of the electrical conductivity (σ) was revealed to be consistent with the adiabatic mechanism of small-radius polaron transport. The increase in the absolute values of the Seebeck coefficient (S) with rising temperature and the decrease in σ above 500 K are attributed to the decrease in the concentration of Mn3+ ions due to their disproportionation into Mn2+ and Mn4+ ions. The equilibrium constants of the disproportionation reaction, carrier concentration and mobility have been derived from the temperature dependencies of S (T) and σ (T) in the conditions when δ ≈ 0. The best values of power factor (S 2 σ) and dimensionless thermoelectric figure-of-merit (ZT = S 2 σT / κ) have been found at the substitution level x = 0.15. [ABSTRACT FROM AUTHOR]

One of the most fascinating aspects of condensed matter is its ability to conduct electricity, which is particularly pronounced in conventional metals such as copper or silver. Such behavior stems from a strong tendency of valence electrons to delocalize in a periodic potential created by ions in the crystal lattice of a given material. In many advanced materials, however, this basic delocalization process of the valence electrons competes with various processes that tend to localize these very same valence electrons, thus driving the insulating behavior. The two such most important processes are the Mott localization, driven by strong correlation effects among the valence electrons, and the Anderson localization, driven by the interaction of the valence electrons with a strong disorder potential. These two localization processes are almost exclusively considered separately from both an experimental and a theoretical standpoint. Here, we offer an overview of our long-standing research on selected organic conductors and manganites, that clearly show the presence of both these localization processes. We discuss these results within existing theories of Mott–Anderson localization and argue that such behavior could be a common feature of many advanced materials. [ABSTRACT FROM AUTHOR]

Here, we report the results of a Mössbauer study on hyperfine electrical and magnetic interactions in quadruple perovskite BiMn7O12 doped with 57Fe probes. Measurements were performed in the temperature range of 10 K < T < 670 K, wherein BiMn6.9657Fe0.04O12 undergoes a cascade of structural (T1 ≈ 590 K, T2 ≈ 442 K, and T3 ≈ 240 K) and magnetic (TN1 ≈ 57 K, TN2 ≈ 50 K, and TN3 ≈ 24 K) phase transitions. The analysis of the electric field gradient (EFG) parameters, including the dipole contribution from Bi3+ ions, confirmed the presence of the local dipole moments pBi, which are randomly oriented in the paraelectric cubic phase (T > T1). The unusual behavior of the parameters of hyperfine interactions between T1 and T2 was attributed to the dynamic Jahn–Teller effect that leads to the softening of the orbital mode of Mn3+ ions. The parameters of the hyperfine interactions of 57Fe in the phases with non-zero spontaneous electrical polarization (Ps), including the P1 ↔ Im transition at T3, were analyzed. On the basis of the structural data and the quadrupole splitting Δ(T) derived from the 57Fe Mössbauer spectra, the algorithm, based on the Born effective charge model, is proposed to describe Ps(T) dependence. The Ps(T) dependence around the Im ↔ I2/m phase transition at T2 is analyzed using the effective field approach. Possible reasons for the complex relaxation behavior of the spectra in the magnetically ordered states (T < TN1) are also discussed. [ABSTRACT FROM AUTHOR]

In this work, we present a detailed investigation of the electrical and optical properties of Pr0.5−xGdxSr0.5MnO3 (0 ≤ x ≤ 0.1) polycrystalline compounds synthesized via a solid-state route. Impedance spectroscopy measurements were performed in the frequency and temperature ranges of 40 Hz–10 MHz and from 80 to 320 K, respectively. DC conductance (GDC) results evince the semiconductor behavior of all studied compounds in the whole temperature range of study. Doping with gadolinium causes a lowering in GDC values and an increase in the activation energies. GDC is shown to be governed by the small polaron hopping model (SPH) at high temperatures and by the variable range hopping (VRH) model at lower ones. The AC measurements show a metallic behavior which can be described by the simplified Drude model. The optical properties were characterized using UV–Vis absorption spectroscopy. By analyzing the UV absorption measurements and based on the Tauc model, we have determined the optical bandgap of each compound evaluated at around 4.5 eV which is a high value compared with those obtained in the literature. The Urbach energy, the optical extinction coefficient, and the refractive index were calculated on the basis of absorbance measurements. In addition, the skin depth, optical conductivity, and the dispersion energy parameters as a function of the wavelength of the incident photon were determined and discussed. These compounds may be interesting in optoelectronic applications. [ABSTRACT FROM AUTHOR]

The mixed-valence perovskite manganites attracted much attention because of their interesting electro-magnetic properties, and strain modulation on magnetic properties of perovskite manganites is worth exploring. In this paper, [La 0. 8 Ca 0. 2 MnO3/La 0. 5 Ca 0. 5 MnO3] 2 0 superlattice films with different La 0. 8 Ca 0. 2 MnO3 layer thicknesses are prepared by pulsed laser deposition (PLD). The crystal structures (lattice constants) of samples are measured by X-ray diffraction (XRD). The strain of the films is determined according to their crystal structures. The magnetic hysteresis loops (M-H loops) and magnetization versus temperature (M-T) curves of these superlattice films are measured by the physical property measurement system (PPMS). From the M-H loops, the coercive field (H C) of the samples can be measured. From the M-T curves, the Curie temperature (T C) of the samples can be obtained. All samples show a ferromagnetic to paramagnetic transition at TC, and the [La 0. 8 Ca 0. 2 MnO3/La 0. 5 Ca 0. 5 MnO3] 2 0 sample with the La 0. 8 Ca 0. 2 MnO3 layer thicknesses of 72 Å has an antiferromagnetic Néel transition at TN. According to the strain state and magnetic phases, the magnetic properties are comprehensively analyzed. It is found that with the increase of ferromagnetic La 0. 8 Ca 0. 2 MnO3 layer thickness, the ferromagnetic phase is increased, and the double exchange effect can also be enhanced, resulting in the increase of TC. When the thickness of La 0. 8 Ca 0. 2 MnO3 reaches 96 Å, the uneven strain distribution in the superlattice can induce the reduction of ferromagnetic phase compared with antiferromagnetic phase (even antiferromagnetic phase starts to appear), and the double exchange effect can be weakened, and finally leading to the decrease of TC. In addition, with increasing the La 0. 8 Ca 0. 2 MnO3 layer thickness, HC gradually decreases. The change of HC is related to strain states and magnetic phase interactions in the samples. The analysis of the strain and magnetism can contribute to the understanding of perovskite manganite superlattice films. [ABSTRACT FROM AUTHOR]

Single-phase, nanosized La0.7Ca0.3Mn1−xNixO3 (x = 0, 0.02, 0.07, 0.1) manganites were synthesized via the autocombustion route. Information on the local geometric structure and the charge state of the Mn ions in the nanosized samples was gleaned from extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) data analysis, respectively. The experimental absorption spectra were recorded at room temperature at the K-edge of the Mn-ions. Analysis of the normalized XANES spectra showed that the Mn formal valence remained practically unchanged upon Ni2+ doping. Nevertheless, the observed broadening of the ruling absorption edge suggested that the repulsive nearest-neighbor potential, stemming from the shortening of the distances of Mn to the nearest-neighbor oxygen atoms (Mn–O bonds) in the coordination shell, was slightly modified. The values of the Mn–O distances were obtained from the Fourier transformed EXAFS spectra. A slight but sizeable decrease in the value of the Mn–O bond distances was verified, which pointed to a slight variation in the Mn3+/Mn4+ ratio sparked by the Ni2+ doping. Here, a generation of more Mn4+ ions with smaller radius (0.53 Å) was expected. The obtained Mn–O distances were compared with those resulting from the Rietveld refinement of the X-ray powder diffraction data. The variation of the 〈Mn–O–Mn〉 bond angle with Ni2+ doping was also determined from the analysis of the X-ray diffraction patterns, which allowed visualizing the small distortion of the MnO6 octahedra on substitution of Mn with Ni2+. [ABSTRACT FROM AUTHOR]

Phase equilibria in the Li–Mn–Eu–O system were studied for the first time in the temperature range 700–1000°С, and a concentration diagram was constructed within the Li–Mn–Eu triangle at an oxygen partial pressure of 21 kPa. It was shown that the LiEuO2–Li2MnO3 section can be represented as quasi-binary, unlike the sections LiEuO2–LiMnO2 and LiEuO2–LiMn2O4. It was determined that the isomorphic substitution of Eu for Mn in spinel LiMn2O4 (Fd m) does not exceed 2 mol %, while Li2MnO3 (C2/m) loses its single-phase character. [ABSTRACT FROM AUTHOR]

The structural, transport and magnetic properties of La0.67Sr0.33MnO3 with additives of ZrO2 and Bi2O3 were investigated and the results are presented. The studied samples showed a ferromagnetic-to-paramagnetic phase transition around 383 K, and a sharp transition was observed for the La0.67Sr0.33MnO3/Bi2O3 sample. A soft ferromagnetic behavior at room temperature was observed in all the La0.67Sr0.33MnO3 samples: however, the sample with bismuth oxide additive exhibited higher saturation magnetization and an enhanced magnetocaloric effect. In addition to a metal–insulator transition, a broad peak was observed in the ferromagnetic metallic region due to inhomogeneities arising from the antiferromagnetic interactions in the samples, and this disappeared with the application of a magnetic field. Positive magnetoresistance was observed for ZrO2 added to La0.67Sr0.33MnO3 for temperatures greater than 200 K. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of the Li–Mn–Eu–O system were obtained by preliminarily ball-milled precursor mixtures annealing in air (700, 800, 900, 1000, and 1100°C). The obtained products were studied by X-ray powder diffraction and thermogravimetry (TG-DSC). The possibility of substituting Mn with Eu for spinel LiMn2–xEuxO4 was assessed. Within the framework of the Li–Mn–Eu concentration triangle, a subsolidus isobaric diagram and a projection of the liquidus surface of the Li–Mn–Eu–O system were constructed using models of polythermal phase diagrams of the LiEuO2–LiMnO2 and LiEuO2–LiMn2O4 sections. The temperatures of eutectic equilibria involving three crystalline phases and a melt were determined. [ABSTRACT FROM AUTHOR]

The extraordinary physical characteristics and enormous potential for technological applications of multiferroic materials have sparked recent interest in these materials. In this work, the composition of aliovalent ions Ba2+/Ti4+ doped YMnO3 i.e., Y0.95Ba0.05Mn0.95Ti0.05O3 ceramic sample was prepared through the solid-state method. The structural, dielectric, and ferroelectric properties of the prepared sample were studied in detail. X-ray diffraction patterns unveil the hexagonal crystal structure of the ceramic owning P63cm space group symmetry, which is also authenticated by accomplishing Rietveld's refinement of the sample. Nevertheless, the ceramic demonstrated the emergence of the orthorhombic peak. The formation of phase composition of the prepared sample was proved through FT-IR spectroscopic measurement. The Raman spectroscopy analysis of the sample reveals the presence of subtle vibrational modes. The investigation of the dielectric and electrical properties of the prepared sample at frequencies between 1 kHz and 1 MHz and temperatures spanning from 303 to 623 K has yielded significant outcomes. These outcomes include dielectric dispersion, conduction mechanism, and relaxation process of the samples, which are highlighted in this study. The ferroelectric behaviour of the prepared sample has been studied using PE hysteresis loop measurement. [ABSTRACT FROM AUTHOR]

This study investigates the interaction between Co and Mn ions on spin state behaviour and magnetic frustration in hole-doped La0.6Dy0.1Ca0.3Co1-xMnxO3 (x = 0-1.0) cobaltite. It aims to understand the inducement of the double-exchange (DE) mechanism in this system. The samples were synthesised using the conventional solid-state synthesis method, and their crystal structure and magnetic properties were analysed. Rietveld refinement of X-ray diffraction data confirmed that La0.6Dy0.1Ca0.3Co1-xO3 (x = 0.0 and 0.2) samples had rhombohedral crystals structure with R c - 3 space group. An orthorhombic (Pbnm) perovskite structure was observed for the La0.6Dy0.1Ca0.3Co1-xMnxO3 (x = 0.4 -1.0) accompanied by increasing cell volume in the samples as the substitution level of Mn increases. Temperature dependence of resistivity p(T) shows semiconducting behaviour in the whole temperature and composition range of x = 0.0-0.8. However, further substitution with x = 0.9 and x = 1.0 give remarkable induced MI behaviour where the MI transition temperature (TMI) increased from 75 K and 132 K, respectively. The result suggests that Mn ions play an important role in the magnetic properties of the cobaltite, and the system can be tuned by adjusting the Mn concentration. [ABSTRACT FROM AUTHOR]

Pr0.67Ba0.33Mn1-xTixO3 (x = 0 and 0.02) were synthesized using a conventional solid-state synthesis method to investigate the effect of Ti substitution on their magnetic and electrical transport properties. All the samples were structurally evaluated by XRD diffraction Rietveld refinement method which showed an increase in unit cell volume with increasing Ni content, indicating that Ti is partially substituted at Mn. Scanning electron microscopy (SEM) and energy dispersive X-tray (EDX) are used to examine the surface morphology and identified elements in the samples' compounds. Fourier transform infrared spectroscopy (FTIR) reveals that all the samples exhibit a transmission band in the range of 590 cm-1 - 610 cm-1. For x = 0, magnetization measurements showed paramagnetic (PM) to ferromagnetic (FM) transition at the transition temperature, TC ~ 213 K. For Ti-substituted samples, ferromagnetic (FM) to PM transition was reduced with Curie temperature (TC), decreasing from 213 K (x = 0) to 205 K (x = 0.02). On the other hand, the M(H) showed the presence of a linear graph for x = 0 and x = 0.02 which may be related to the presence of paramagnetic at room temperature. [ABSTRACT FROM AUTHOR]

The present report focuses on the successful synthesis of La0.7Ca0.3−xAgxMnO3 (x = 0, 0.10, 0.15, 0.20, and 0.30) polycrystalline manganite samples through a soft chemical polymeric precursor route and subsequent impact of Ag doping and grain size on their magnetotransport features. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses reveal that Ag doping leads to a phase transformation from the orthorhombic phase to the rhombohedral phase (for x ≥ 15%). Furthermore, it shows that the insulator–metal transition temperature (TIM) and paramagnetic–ferromagnetic (PM-FM) transition temperature (TC) increase with Ag doping concentration and also with the sintering temperature. The prime factors leading to the enhancement with Ag doping are the well-known oxygenation effect by metallic Ag, which helps to improve the transport properties of La1−xCaxMnO3 (LCMO) manganite, and the increase in the tolerance factor (τ), which in turn leads to the Mn-O-Mn bond angle and the structural disorder near the grain boundaries that weaken the double exchange. The room temperature magnetoresistance values are found to be higher for Ag-doped LCMO samples than for the pristine LCMO. The enhanced ferromagnetic ordering temperature along with low-field magnetoresistance (LFMR) of the as-synthesized Ag-doped LCMO polycrystalline ceramic indicate its potential for device fabrication. [ABSTRACT FROM AUTHOR]

Perovskite-type Ca0.5 –xSr0.5LuxMnO3 – δ (x = 0.05, 0.10, 0.15, and 0.20) manganites have been prepared in air using a citrate–nitrate process for preparing precursors. At room temperature, the x = 0.05, 0.10, and 0.15 samples have an orthorhombic structure (space group Pbnm); when x = 0.2, a tetragonal structure (space group I4/mcm) is formed. The increase in unit cell volume in response to rising lutetium concentration in the samples is due to an increase in Mn3+ concentration necessary to ensure n-type electrical conductivity σ. The temperature-activated electrical conductivity is consistent with the adiabatic transport mechanism of small polarons. The increase in magnitude of the Seebeck coefficient S in response to rising temperature is due to the decrease in the concentration of Mn3+ ions via their disproportionation to Mn2+ and Mn4+ ions. The S(T) and σ(T) temperature dependences under the condition where δ ⁓ 0 have been used to calculate the equilibrium constants of the disproportionation reaction, charge carrier concentrations and mobilities. [ABSTRACT FROM AUTHOR]

Highlights: Orthorhombic Eu1−xYxMnO3 (0.0 ≤ x ≤ 0.5) thin films were successfully synthesized by spin-coating. The film phase evidences an additional contribution to lattice strain with increasing Y-content. Appreciable modification of magnetic response from bulks to films due to structural distortions. The effects on the structure and magnetic properties of Eu1−xYxMnO3 (0.0 ≤ x ≤ 0.5) thin films due to lattice strain were investigated and compared with those obtained in equivalent composition ceramics. The films were deposited by spin-coating chemical solution onto Pt\TiO2\SiO2\Si (100) standard substrates. X-ray diffraction and Raman spectroscopy measurements revealed that all films crystallize in orthorhombic structure with space group Pnma, observing an added contraction of the unit cell with increasing Y-substitution ou Eu, corresponding to a broadening of the Mn-O1-Mn angle and a gradual decrease in magnetic order response. [ABSTRACT FROM AUTHOR]

A La0.7Sr0.3−xSmxMn0.95Ni0.05O3 (x = 0, 0.05, 0.10, 0.15) series of manganites were synthesized by the Pechini sol–gel method. The changes in structure and magnetic properties caused by the substitution of Sr2+ by Sm3+ were systematically investigated. The results of Rietveld refinement using GSAS (General Structure Analysis System) software showed that the samples had a rhombohedral structure before and after the substitution, but the cell volume increased. In addition, the Curie temperature (TC) of the samples gradually decreased with increased doping, and the magnetic entropy change ( Δ S M ) showed the same trend. This can be attributed to the weakening of the ferromagnetic coupling between Mn4+ and Mn3+. For the doped sample with x = 0.05, the TC was 300 K, and the maximum magnetic entropy change ( - Δ S M max ) reached 4.59 J kg−1 K−1 at an applied magnetic field of 5 T. The relative cooling power (RCP) also reached 297.39 J kg−1, which is certainly promising for meeting the need for room-temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Here we report the synthesis and investigation of bulk and nano-sized La0.7Ba0.3−xCaxMnO3 (x = 0, 0.15, 0.2 and 0.25) compounds that are promising candidates for magnetic refrigeration applications. We compare the structural and magnetic properties of bulk and nano-scale polycrystalline La0.7Ba0.3−xCaxMnO3 for potential use in magnetic cooling systems. Solid-state reactions were implemented for bulk materials, while the sol–gel method was used for nano-sized particles. Structurally and morphologically, the samples were investigated by X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). Oxygen stoichiometry was investigated by iodometry. Bulk compounds exhibit oxygen deficiency, while nano-sized particles show excess oxygen. Critical magnetic behavior was revealed for all samples using the modified Arrott plot (MAP) method and confirmed by the Kouvel–Fisher (KF) method. The bulk polycrystalline compound behavior was better described by the tricritical field model, while the nanocrystalline samples were governed by the mean-field model. Resistivity in bulk material showed a peak at a temperature Tp1 attributed to grain boundary conditions and at Tp2 associated with a Curie temperature of Tc. Parent polycrystalline sample La0.7Ba0.3MnO3 has Tc at 340 K. Substitution of x = 0.15 of Ca brings Tc to 308 K, and x = 0.2 brings it to 279 K. Nanocrystalline samples exhibit a very wide effective temperature range in the magnetocaloric effect, up to 100 K. Bulk compounds exhibit a high and sharp peak in magnetic entropy change, up to 7 J/kgK at 4 T at Tc for x = 0.25. To compare the magnetocaloric performances of the studied compounds, both relative cooling power (RCP) and temperature-averaged entropy change (TEC) figures of merit were used. RCP is comparable for bulk polycrystalline and nano-sized samples of the same substitution level, while TEC shows a large difference between the two systems. The combination of bulk and nanocrystalline materials can contribute to the effectiveness and improvement of magnetocaloric materials. [ABSTRACT FROM AUTHOR]

Industrial effluents containing dyes are a serious threat to the ecosystems and the removal of these dyes is most often conducted by adsorption. In this study, Sr-doped lanthanum (LSMO), calcium (CSMO) and barium (BSMO) manganites were prepared by the autocombustion and co-precipitation synthesis, and tested as the adsorbents for the removal of methyl orange (MO) as a model pollutant from the aqueous solution. The highest adsorption of the MO solution obtained by CSMO adsorbents was 83.5%, while the highest adsorption of 95% was achieved using LSMO and BSMO due to their large specific surface area and average pore diameter promoting the diffusion of the MO to the adsorbent surface. The oxygen nonstoichiometry of these materials also contributed to their adsorption properties due to the presence of unpaired electrons, which affected their electronic structure and lowered the adsorption energy. Kinetic studies showed that Ho’s pseudo-second-order model exhibited the best fit with the experimental data, indicating that chemisorption is the rate-limiting step. The rate constants were the highest for BSMO adsorbents ranging from 3.35 to 3.50 × 10–2 g mg–1·min–1. The adsorbents can be fully regenerated by calcining at 700°C for 2 h with no loss of their activity. [ABSTRACT FROM AUTHOR]

Nanocrystalline La0.9A0.1Mn0.9Cr0.1O3 (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology were studied using X-ray diffraction (XRD), Raman spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDS) and Scanning electron microscopy (SEM). Magnetic properties were studied using magnetometry methods and the valency changes of the cations after alkali ions doping were studied using X-ray photoelectron spectroscopy (XPS). The influence of the sintering pressure on the structural and magnetic properties of the manganites doped with different alkali ions and chromium was also investigated. Magnetization properties were studied as a function of sintering pressure and type of the dopant. Chemical doping with alkali ions as well as external pressure significantly changed the magnetic properties of the compounds. It was found that the magnetic properties of the manganites could be predictably modified through the use of a suitable dopant element. [ABSTRACT FROM AUTHOR]