Perovskite Manganites Research Articles

Tuning the magnetocaloric and structural properties of La0.67Sr0.28Pr0.05Mn1–xCoxO3 refrigeration materials

Abstract The structural, magnetic and magnetocaloric properties of perovskite manganites La0.67Sr0.28Pr0.05Mn1−x Co x O3 (x = 0.05, 0.075 and 0.10) (LSPMCO) are investigated. LSPMCO crystallizes as a rhombohedral structure with R-3c space group. As the Co content increases, the cell volume expands, the Mn–O–Mn bond angle reduces and the length of the Mn–O bond increases. The samples show irregular submicron particles under a Zeiss scanning electron microscopy. The particle size becomes larger with increasing doping. The chemical composition of the samples is confirmed by x-ray photoelectron spectroscopy (XPS). The ferromagnetic (FM) to paramagnetic (PM) phase transition occurs near the Curie temperature (T C), and all transitions are second-order phase transitions (SMOPT) characterized by minimal thermal and magnetic hystereses. Critical behavior analysis indicates that the critical parameters of LSPMCO closely align with those predicted by the mean-field model. The T C declines with Co doping and reaches near room temperature (302 K) at x = 0.075. The maximum magnetic entropy change ( − Δ S M max ) at x = 0.05 is 4.27 J/kg⋅K, and the relative cooling power (RCP) peaks at 310.81 J/K. Therefore, the system holds significant potential for development as a magnetic refrigeration material, meriting further professional and objective evaluation.

Structural, electronic and optical properties of SrMnO3 photocatalyst for dye degradation; experimental and DFT study

Perovskite oxides (PO) are versatile multi-functional materials with wide range of applications. In current study, highly-crystalline perovskite manganite (PM) SrMnO3 has been synthesized via ultrasonic method followed by calcination at 600 °C. Morphology of PM with irregular shape and size was assessed by FESEM and hexagonal geometry with a crystallite size of 13.67nm was determined by XRD studies. As-synthesized PM was further tested as photocatalyst for its dye degradation potential against malachite green (MG) and methylene blue (MB). In the presence of synthesized perovskites, degradation of both the dyes MG and MB was achieved in 12min and 4.5min with the percentage degradation of 80.26% and 89.35% respectively. The factors including pH and temperature affecting degradation of both the dyes were also studied. Additionally, calculations based on simulated DFT (density function theory) have been employed to explore the optical, electronic and structural attributes of SrMnO3 PM through generalized gradient approximation (GGA). The total and partial density of states have been evaluated by GGA confirms the Fermi level (Ef) characteristics of metallic Sr and Mn and found that ‘d’ and ‘p’ orbitals of Sr, Mn and O were responsible for the band formation. The results of the current study advocate the synthesis of PM and related compounds followed by their successful applications as catalyst for dye degradation as well as many other fields involving the use of nanomaterials.

The structure, magnetic properties, magnetotransport and temperature coefficient of resistivity of hexagonal 4H-SrMnO3 manganite

The perovskite hexagonal SrMnO3 manganite with four layers (4H-SrMnO3) have been one of the hot topics in materials science due to the physical characteristics of antiferromagnetic, ferroelectric, and thermoelectric effects. The transport properties and magnetoresistance (MR) effect of 4H-SrMnO3 have seldom been reported. The structure, temperature coefficient of resistivity (TCR), magnetic and magnetotransport properties of the 4H-SrMnO3 SrMnO3 manganite obtained by solid state reaction have been investigated in this work. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements at room temperature reveal that the SrMnO3 sample exhibits a pure hexagonal symmetric structure, with uniform distribution of particles and elements. Under applied magnetic fields of 2000 Oe, the SrMnO3 sample exhibits a transition from antiferromagnetic (AFM) to paramagnetic (PM) behavior at approximately 280 K, known as the Néel temperature (TN). The resistance is influenced by the magnetic field, but overall exhibits an insulating state. Remarkably, the SrMnO3 sample shows significant MR effect near room temperature. The negative MR near room temperature varies from 5.8 % with 1 T field to 16.8 % with 6 T field, indicating an existence of obvious MR in the hexagonal AFM SrMnO3 manganite. Furthermore, the maxmium value of TCR reaches 4.34 % K−1 near room temperature. These findings of room-temperature TCR and room-temperature MR in the AFM 4H-SrMnO3 hold immense value for the research and potential application of the AFM spintronics and devices.

Magnetic exchange coupled composite behavior in the doped manganite nanoparticles: A proposed phenomenological model

In this paper, we comprehensively investigate the isothermal magnetization behavior of doped perovskite manganite nanoparticles. The focus is on understanding the impact of variation of particle sizes on the soft and hard magnetic phases with respect to the changes in the coercive field and remanent magnetization, both theoretically and experimentally. The study seeks to correlate experimental findings with the proposed phenomenological model to gain deeper insights into the underlying mechanisms governing exchange coupling and anisotropy effects in the nanocrystalline composites. The proposed phenomenological model beautifully demonstrates how the values of saturation magnetization and coercive field changes with changing the particle size in the nanocrystalline La0.48Ca0.52MnO3 (LCMO48) and La0.46Ca0.54MnO3 (LCMO46) compounds. In addition, the model provide an insights into the limitations of critical radius, size and shape of the nanocrystalline particle. This investigation looks into how the size of particles affects their magnetic properties, specifically coercive field and remanent magnetization.

Copper-perovskite interfacial engineering to boost deNOx activity

By adjusting the Cu doping level and calcination temperature during synthesis of a series of noble metal-free lanthanum copper manganite perovskites LaCuxMn1-xO3, we show the importance of tuning the redox chemistry for optimum steering of the catalytic activity and N2 selectivity in the catalytic reduction of NO by CO. A prerequisite is the in situ formation of an extended copper-perovskite phase boundary. The associated improvement of redox and surface properties by Cu addition leads to an optimized balance of the reduction of the catalyst in the NO+CO reaction mixture. The creation of oxygen vacancies improves the reaction kinetics and initiates the NO dissociation. Strongly dependent on the calcination temperature, the Cu/Mn ratio, the reducing agent, as well as the reaction temperature as parameters for Cu-perovskite interfacial control, surface reduction can induce partial copper exsolution, significant perovskite reduction, agglomeration of exsolved Cu particles and eventual decomposition of the catalyst structure. We show that increasing the amount of initial copper incorporated into the perovskite structure can beneficially extend the phase boundary, but exceeding the amount of copper leads to increased sintering of the copper particles at the expense of catalyst activity, especially in repeated catalytic cycles. Increasing the calcination temperature, in addition to the initial sintering of the catalyst and shifting the reaction onset temperature to higher temperatures in the first cycle, improves the reduction resistance of the catalyst. Consequently, in order to form a higher amount of phase boundary-bound active sites, stronger reducing conditions than provided by the NO+CO reaction mixture are needed. This effect can be counterbalanced by using stronger reduction agents prior to performing subsequent catalytic cycles by inducing the exsolution process.

Study of structural, Griffiths phase, and magneto-crystalline anisotropy in Pr0.47La0.20K0.33Mn0.91Cu0.09O3 perovskite manganite

Study of structural, Griffiths phase, and magneto-crystalline anisotropy in Pr0.47La0.20K0.33Mn0.91Cu0.09O3 perovskite manganite

Performance of a perovskite-structured calcium manganite oxygen carrier produced from natural ores in a batch reactor and in operation of a chemical-looping combustion reactor system

The potential for low cost of CO2 capture using chemical-looping combustion (CLC) should not be compromised by costs associated with the oxygen carrier. This justifies studies of oxygen carrier materials with reasonable production costs. In this study, a perovskite calcium manganite (CaMnO3-δ), was synthesized from manganese ore and limestone through a straightforward process involving mixing with polyvinyl-alcohol, sintering, crushing and sieving. The calcium manganite produced exhibited two primary crystalline phases: CaMnO3 (perovskite) and CaMn2O4 (marokite). Experiments were conducted using both a batch fluidized-bed reactor and a 300 W CLC reactor system in continuous operation to assess the oxygen uncoupling and reactivity of the calcium manganite. The results show that the oxygen uncoupling ability increases with temperature. Full syngas conversion was achieved at relatively low temperatures and low fuel-reactor bed mass over fuel power ratio in the 300 W unit. Elevated temperatures and ratio of fuel-reactor bed mass over fuel power enhance methane conversion significantly. The attrition of the calcium manganite was low, around 0.1 wt%/h for the last 15 h operation with methane. Batch reactor tests of fresh and used materials showed that there was no reduction in reactivity after 29 h of fuel operation.

Highly Recyclable and Versatile La0.5Nd0.2Ca0.3MnO3 and La0.5Nd0.2Ca0.25K0.05MnO3 Perovskite Catalysts for Effective Removal of Organic Contaminants

AbstractWastewater contamination, particularly from dye effluents containing organic colorants originating from industrial sources, represents a significant environmental and public health hazard. This study is dedicated to removal of these abundant coloured effluents in wastewater, addressing the imperative need for effective remediation strategies to safeguard ecosystems and human well‐being. In this regard, bare and K‐doped perovskite manganites La0.5Nd0.2Ca0.3MnO3 (LCM) and La0.5Nd0.2Ca0.25K0.05MnO3 (LCKM) nanoparticles respectively were synthesized in order to study their catalytic behaviour for degradation of coloured effluents. The Rietveld analysis applied to the X‐ray diffraction data provides confirmation of orthorhombic symmetry. For exploring the catalytic properties, rhodamine‐B (RhB) dye was chosen as model dye pollutant. The achieved degradation efficiency is substantial, reaching 99 % within a brief period of 10–12 min. Following these results, we have also carried out the degradation of some other dyes such as methylene blue (MB) and methyl orange (MO). It was observed that MO dye was more efficiently degraded in quick time as compared to all the other dyes due to its anionic nature. Furthermore, the comparative catalytic efficiencies of LCM and LCKM catalysts were explained on the basis of Mn3+/Mn4+ redox pairs and it was observed that LCKM had shown better degradation efficiency than LCM.

Multifaceted Roles of Ag+ Ions within and outside La–Ca–MnO3 Perovskite Manganites: Unveiling the Room Temperature Magnetocaloric Effect

Multifaceted Roles of Ag⁺ Ions within and outside La–Ca–MnO₃ Perovskite Manganites: Unveiling the Room Temperature Magnetocaloric Effect

Kinetics of the CH4/O2 reaction over supported palladium catalysts on K-doped manganite perovskite: Impact of potassium on the nature of Pd-support interface and related reaction mechanisms

The kinetics of the CH4/O2 reaction, occurring on post-combustion catalysts to treat the exhaust gases of natural gas-powered engines, has been investigated in lean conditions on model Pd catalysts supported on K-doped LaMnO3. Experimental and predicted reaction rates have been compared according to a single site on Pd active sites and dual site reaction mechanism on active sites located at the Pd-perovskite interface. Comparisons with a benchmark Pd/LaMnO3 emphasized significant changes induced by thermal aging at 750 °C in wet atmosphere (10 vol% H2O in 5 vol% O2). Indeed, the contribution of the single site mechanism grows on aged Pd/LaMnO3 emphasizing a deterioration of the Pd-LaMnO3 interface. The opposite trend is observed on Pd/La1−xKxMnO3 with kinetics obeying to a single site mechanism on pre-reduced catalyst and then shifting to a quasi-exclusive dual site mechanism after aging. Such kinetic features have been discussed with respect to bulk and surface physicochemical characterization pointing out the key role of potassium in the stability of the Pd-support interface.

Strained single crystal high entropy oxide manganite thin films

The ability to accommodate multiple principal cations within a single crystallographic structure makes high entropy oxides (HEOs) ideal systems for exploring new composition–property relationships. In this work, the high-entropy design strategy is extended to strained single-crystal HEO-manganite (HEO-Mn) thin films. Phase-pure orthorhombic films of (Gd0.2La0.2Nd0.2Sm0.2Sr0.2)MnO3 were deposited on three different single-crystal substrates: SrTiO3 (STO) (100), NdGaO3 (110), and LaAlO3 (LAO) (100), each inducing different degrees of epitaxial strain. Fully coherent growth of the thin films is observed in all cases, despite the high degree of lattice mismatch between HEO-Mn and LAO. Magnetometry measurements reveal distinct differences in the magnetic properties between epitaxially strained HEO-Mn thin films and their bulk crystalline HEO counterparts. In particular, the bulk polycrystalline HEO-Mn shows two magnetic transitions as opposed to a single one observed in epitaxial thin films. Moreover, the HEO-Mn film deposited on LAO exhibits a significant reduction in the Curie temperature, which is attributed to the strong variation of the in-plane lattice parameter along the thickness of the film and the resulting changes in the Mn–O–Mn bond geometry. Thus, this preliminary study demonstrates the potential of combining high entropy design with strain engineering to tailor the structure and functionality of perovskite manganites.

Local lattice distortions and electronic phases in perovskite manganite Pr0.5Sr0.5MnO3

We use variable temperature and magnetic field total x-ray scattering to study the crystal structure of the strongly correlated Pr0.5Sr0.5MnO3 perovskite, which is a paramagnetic insulator at room temperature, becomes a ferromagnetic metal at 272 K and, upon further decreasing the temperature, turns into an antiferromagnetic insulator at 105 K. We find that a model featuring a monoclinic symmetry captures the structure and its temperature and field evolution well, eliminating the need to evoke a phase segregation scenario as done in prior studies. It appears that coupled variations in Mn–oxygen bonding distances and angles from their values in an undistorted perovskite lattice, i.e., coupled local lattice distortions, assist the phase transitions in Pr0.5Sr0.5MnO3, contributing to its unique physical properties. Local structural distortions thus emerge as an important degree of freedom in strongly correlated systems, in particular perovskite manganates, and, therefore, they should be fully accounted for when their fascinating physics is considered.

Rietveld Refinement, Structural Morphology and Magnetic Properties of La0.57Sm0.1Sr0.33−xBaxMnO3 Manganite Nanoparticles

Lanthanide-based manganite perovskites due to their possible integration both in conventional Si-based electronics, and in innovative full-oxide electronics, have led to a massive resurgence of interest. The properties and applicability of these perovskites can be tailored with the interplay of foreign ion substation, and thus lot of efforts have been made by the researchers by using various types of compound combinations. In this work, a systematic study of Ba-substituted lanthanide of a chemical formula La[Formula: see text]Sm[Formula: see text]Sr[Formula: see text]Ba[Formula: see text]MnO3 (where, [Formula: see text], 0.05, 0.1, 0.20 and 0.33) was done and the manganites were synthesized by sol–gel auto-combustion method. The structural and magnetic properties were investigated by thermogravimetric/differential thermal analysis, which was also carried out to investigate the thermal stability of the prepared samples. X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM), scanning electron microscopy (SEM) etc. were employed to investigate the crystallographic structure. XRD patterns and selected area electron diffraction patterns revealed the formation of single-phase La[Formula: see text]Sm[Formula: see text]Sr[Formula: see text]Ba[Formula: see text]MnO3 perovskite materials without any signature of secondary phases. Elemental composition of the synthesized samples was investigated by the energy dispersive analysis of X-ray analysis, which confirmed the expected stoichiometry of the prepared samples. TEM and SEM observations revealed the nano-crystalline nature of the prepared samples, where particle size obtained from TEM ranges from 40[Formula: see text]nm to 70[Formula: see text]nm. It has been found that structural and magnetic properties of the parent La[Formula: see text]Sm[Formula: see text]Sr[Formula: see text]MnO3 system were greatly affected by the Ba substitution.

Terahertz photon to dc current conversion via magnetic excitations of multiferroics

Direct conversion from terahertz photon to charge current is a key phenomenon for terahertz photonics. Quantum geometrical description of optical processes in crystalline solids predicts existence of field-unbiased dc photocurrent arising from terahertz-light generation of magnetic excitations in multiferroics, potentially leading to fast and energy-efficient terahertz devices. Here, we demonstrate the dc charge current generation from terahertz magnetic excitations in multiferroic perovskite manganites with spin-driven ferroelectricity, while keeping an insulating state with no free carrier. It is also revealed that electromagnon, which ranges sub-terahertz to 2 THz, as well as antiferromagnetic resonance shows the giant conversion efficiency. Polar asymmetry induced by the cycloidal spin order gives rise to this terahertz-photon-induced dc photocurrent, and no external magnetic and electric bias field are required for this conversion process. The observed phenomena are beyond the conventional photovoltaics in semi-classical regime and demonstrate the essential role of quantum geometrical aspect in low-energy optical processes. Our finding establishes a paradigm of terahertz photovoltaic phenomena, paving a way for terahertz photonic devices and energy harvesting.

Synthesis and magnetic properties of perovskite manganite La0.8Ca0.15Na0.05Mn0.8Fe0.2O3

Synthesis and magnetic properties of perovskite manganite La0.8Ca0.15Na0.05Mn0.8Fe0.2O3

Scalable and environmentally friendly production of perovskite manganite thin films for neuromorphic applications

A method of producing high-quality thin films of perovskite manganites utilizing citrate-based aqueous chemical solution deposition is presented. The method is applied to the production of thin films of gadolinium calcium manganite, Gd1−xCaxMnO3 (GCMO). The film quality is verified by x-ray diffraction analysis, electron microscopy, and magnetic measurements. Finally, planar memristors are fabricated using GCMO films, demonstrating the material’s ability to exhibit resistive switching. This underscores its potential for future memristor technologies.

Enhancing future technologies: Sol-Gel synthesis of Sr0.6Ag0.4MnO3 manganite perovskite

The research successfully produced Sr0.6Ag0.4MnO3, a silver strontium manganite with the desired perovskite crystal structure, using the sol-gel technique. Extensive analysis revealed its notable characteristics, indicating potential uses across various fields. X-ray diffraction showed the compound's tetragonal structure at room temperature, affirming its stability. Morphological and chemical assessments confirmed the material's consistency and evenness, with crystallites averaging 27 nm (from XRD) and 90 nm (from SEM). The material displayed a ferro-paramagnetic transition at 375 K, suggesting suitability for magnetic applications, alongside a slight drop in electrical resistance under a magnetic field, hinting at potential magnetoresistive properties for electronic devices. In terms of dielectric properties, particularly at low frequencies, the material demonstrated a high dielectric constant and low tangent loss, indicating its potential for electrical components. Overall, these findings position Sr0.6Ag0.4MnO3 as a versatile material with promising applications in magnetism, electronics, and electrical components.

Multisublattice Magnetic Structures in Charge Ordered Perovskite Manganites with High Doping Level

Multisublattice Magnetic Structures in Charge Ordered Perovskite Manganites with High Doping Level

Excess antimony induced 12R Ba4Sb0.85Mn3.15O12 phase and Mn3O4 exsolution from 10H Ba5Sb0.7Mn4.3O15: Crystal structure and magnetic properties

Hexagonal perovskite manganite has attracted much attention due to its rich structural chemistry and magnetic properties. The transformation between BaMxMn1−xO3 polymorphs can be caused by the change in substitution level or oxygen vacancies. In this study, we find a new polymorph change from 10H Ba5Sb0.7Mn4.3O15 (P63/mmc) to 12R Ba4Sb0.85Mn3.15O12 (R3‾m) via a ‘topochemical’ reaction with excess Sb2O3. The 10H Ba5Sb0.7Mn4.3O15 structure contains BaO3 layers in a (cchhh)2 sequence and face-shared MnO6 tetramers (Mn4 clusters), while the 12R Ba4Sb0.85Mn3.15O12 structure consists of BaO3 layers in a (cchh)3 stacking and face-shared MnO6 trimers (Mn3 clusters). The 10H → 12R phase conversion accompanies the exsolution of the Mn3O4 phase in trace amounts. For both 10H Ba5Sb0.71Mn4.29O15 and 12R Ba4Sb0.85Mn3.15O12, the Mn3+ cation on the corner-shared octahedra at M1 sites mediated competing ferromagnetic and antiferromagnetic exchanges between the magnetic Mn3 and Mn4 clusters, leading to spin-freezing transition at TF ≈ 11–15 K. The 10H → 12R phase change leads to an abrupt change of 2 K saturation moment from Ms ≈ 0.1 μB of 10H Ba5Sb0.71Mn4.29O15 to Ms ≈ 1.75 μB of 12R Ba4Sb0.85Mn3.15O12.

The production system and structural characterization of CAMNi-xTIxO3 with x values ranging from 0.0 to 1.0 are investigated

In this work, we report the production of new composite perovskite manganite system CaMn ,Ti,O, with doping x = 0.25, 0.5 and 0.75, reaction sintering method solid state. Structural characterization was performed using the technique of X-ray Diffraction (XRD) and the Rietveld method, obtaining a tetragonal structure, with Prima spatial group (# 62) (a=5.3586a y a=5.2997A: b=7.5041 A y b=7.5526a; c+5.3l82& y c=5.3278A). In this paper takes the discussion on possible structural changes with changes in the system titanium CaMn, ,Ti,O,.