MnO3 System Research Articles

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.

Admittance spectroscopy investigation of Pr0.65Ca0.25Sr0.1MnO3 system

Admittance spectroscopy investigation of Pr0.65Ca0.25Sr0.1MnO3 system

La0.6X0.1Te0.3MnO3 system with significant refrigerant capacity at low magnetic field and double magnetic entropy change peaks: effect of ball-milling time on physical and critical behaviors

We have investigated the ball-milling time effect on different physical properties of La0.6X0.1Te0.3MnO3 (X is a lacuna) system (LT) milled for 1 h (LT-1h), 3 h (LT-3h), and 6 h (LT-6h). According to Williamson-Hall method, as the ball-milling duration is increased, the material’s crystallite size decreases from approximately 145 to 99 nm for LT-1h and LT-6h, respectively. Electronic study was also investigated. The Zero-Field-Cooling and Field-Cooling (ZFC/FC) magnetization measurements illustrated that all the systems are presenting a ferromagnetic to paramagnetic phase transition around Curie temperature (TC). This transition is around 176, 182, and 183 K accompanied by a decrease in the magnitude in both ZFC and FC data. Thus, increasing the ball-milling time of the sample leads to the elevation of TC and does not enhance the magnitude of the magnetization the fact that it affects the magnetic interactions between atoms. By increasing the ball-milling duration, the proportion of homogeneity is increased, and the material becomes slightly more resilient, according to the Curie-Weiss law. Additionally, it is accompanied with an increase in coercivity and a decrease in the saturation magnetization and remanence. Based on the AC-susceptibility, raising the ball-milling time facilitates the appearance of a spin-glass (SG) state. The relative cooling power (RCP) value in the LT-1h sample at 2 T is 108% (211.758 J kg−1) compared to that of the Gd at 2 T. Consequently, the LT sample could be a permanent magnet in a magnetic refrigerator. Noting that raising the ball-milling time weakens the RCP. Both LT-1h and LT-3h systems are belonging to the tricritical mean field model. However, for LT-6h, the model changed and the best one became the 3D-Ising model. Hence, the ball-milling time influences also the universality class.

Effects of laser floating zone processing on electrical and magnetic properties of (Ca,Pr)MnO3 system

Manganites present fascinating physical properties which can be tuned according with the method and processing conditions. In this work, Ca1-xPrxMnO3 (x = 0.03, 0.06, 0.1) materials were prepared by the Laser Floating Zone (LFZ) technique, under different pulling rates (25–100 mm/h) in air and argon atmospheres, obtaining fibres with 2.5 mm diameter. Such processing conditions promote the formation of secondary phases in (Ca,Pr)MnO3 fibres. The formation of the perovskite phase at slow pulling rates was observed. The effects of the LFZ conditions on the phase composition, microstructural features, electric and magnetic properties of as-grown and thermally post-processed fibres are analysed and discussed. The results indicate that the LFZ processing conditions have a great impact on the electrical and magnetic properties of the prepared manganites. Secondary phases increase with pulling rate and the effects imposed by their formation can be minimized by additional heat treatment at high temperatures, improving the electric conductivity and magnetization of the thermally-treated fibres.

Ferroelectric-polarization modulation of charge-to-spin conversion in Pb(Mg1/3Nb2/3)O3–Pb0.7Ti0.3O3/La0.67Sr0.33MnO3 system

Modulation of charge-to-spin conversion through active control is supposed to manipulate efficiency in a wide range for future spintronic devices. Despite its great significance, passive control still dominates the manipulation while the active control of charge-to-spin conversion is still challenging. Here we experimentally observe spin pumping-type charge-to-spin conversion besides Rashba-type one in La0.67Sr0.33MnO3 thin films deposited on ferroelectric Pb(Mg1/3Nb2/3)O3–Pb0.7Ti0.3O3 (PMN-PT) substrate. We exhibit that both two types of charge-to-spin conversion efficiency give rise to a variety of sign under positive and negative remnant polarized states of PMN-PT, which can be ascribed to the effect of ferroelectric polarization. The possibility of modulating charge-spin conversion opens a route for designing low-energy spintronics.

Erratum to: Formation of Gapless Z2 Spin Liquid Phase Manganites in the (Sm1 – yGdy)0.55Sr0.45MnO3 System in Zero Magnetic Field: Topological Phase Transitions to States with Low and High Density of 2D-Vortex Pairs Induced by the Magnetic Field

Erratum to: Formation of Gapless Z2 Spin Liquid Phase Manganites in the (Sm1 – yGdy)0.55Sr0.45MnO3 System in Zero Magnetic Field: Topological Phase Transitions to States with Low and High Density of 2D-Vortex Pairs Induced by the Magnetic Field

Effect of varying milling time on the formation of La0.9Sr0.1MnO3 for IT-SOFC

Lowering the sintering temperature of cathode material for intermediate temperature solid oxide fuel cell (IT-SOFC) is the main concern of current research. In the present work, well-known La0.9Sr0.1MnO3 system as cathode for IT-SOFC was prepared by using mechanochemical synthesis by varying the grinding time. The pure phase La0.9Sr0.1MnO3 forms after dry milling at 24 h with 500 rpm. X-ray diffraction confirms single crystalline rhombohedral phase of as-synthesized and sintered La0.9Sr0.1MnO3. Sintering at 700 °C improves the degree of crystallinity. Scanning electron microscope images of as-synthesized samples reveal highly agglomerate fine-scale grains. The temperature dependence of DC conductivity curve exhibits linear dependence of conductivity with temperature.

Synthesis and Characterization of La0.70Ca0.30MnO3 System for Solid Oxide Fuel Cell Applications

La0.70Ca0.30MnO3 system has been prepared by solid state reaction method for cathode of solid oxide fuel cell applications. The structural studies have been investigated by X-Ray diffraction method and the experimental results have confirmed that the prepared system has been well crystallized into single phase, crystal structure is orthorhombic and size of the particle has been calculated to be 0.35 μm. The surface morphology has been studied by scanning electron microscopy which confirmed that grain sizes are irregular, non uniform and randomly oriented. Archimedes principle has been used to investigate the density of the prepared material. Thermal properties of the system confirmed its stability at high temperature and thermal expansion coefficient well matched with other cell components. The dielectric as well as impedance properties have been investigated at different ranges of temperature and frequency. Electrical conductivity of the prepared system has been found to be more than 100 S/cm as well as obtained value of activation energy signifies that the synthesized system is suitable for cathode of solid oxide fuel cell applications.

The Effect of Ball-Milling Time on the Physical and Critical Behaviors of a La0.6◻0.1te0.3mno3 System with Double Magnetic Entropy Change Peaks and Significant Refrigerant Capacity at Low Magnetic Field

The Effect of Ball-Milling Time on the Physical and Critical Behaviors of a La0.6◻0.1te0.3mno3 System with Double Magnetic Entropy Change Peaks and Significant Refrigerant Capacity at Low Magnetic Field

Correlating X-ray absorption spectra and ultraviolet photoelectron spectra to understand magnetic and transport properties of charge-ordered perovskite manganites

X-ray absorption spectra and ultraviolet photoelectron spectra have been used to compare the electronic structures of (La0.6Pr0.4)0.65Ca0.35MnO3 and (La0.4Pr0.6)0.65Ca0.35MnO3 systems to understand their magnetic and transport properties. Structural analysis showed that increased Pr-substitution triggers expansion in apical Mn-O bond lengths, which eventually causes narrowing of the eg band width. (La0.6Pr0.4)0.65Ca0.35MnO3 exhibits ferromagnetic ordering below 215 K and shows semiconductor to metal transition around 212 K, while (La0.4Pr0.6)0.65Ca0.35MnO3 exhibit complex magnetic behaviour and also show local semiconductor to metal transition around 95 K before re-entering into semiconducting region again below 80 K. A slight change in the slope of resistivity around 220 K and four orders increase in resistivity indicates presence of charge-ordering in (La0.4Pr0.6)0.65Ca0.35MnO3. Moreover, (La0.4Pr0.6)0.65Ca0.35MnO3 exhibits ~ 100% magneto-resistance. X-ray absorption studies of Mn-L2,3 edge and O-K edge reveal the onset of Mn3+-Mn4+ charge-ordering in (La0.4Pr0.6)0.65Ca0.35MnO3 at room temperature. O-K edge spectra exhibits an increased spectral intensity of O2p-Mn3d(eg) states near Fermi-level for (La0.4Pr0.6)0.65Ca0.35MnO3, which reflects the number of unoccupied eg states. Valence band ultraviolet photoemission spectroscopy study revealed that Mn3d(eg) states of (La0.6Pr0.4)0.65Ca0.35MnO3 extends into conduction band by crossing-over the Fermi-level. On the other hand, (La0.4Pr0.6)0.65Ca0.35MnO3 exhibits no electronic state at Fermi-level explaining stronger semiconducting nature of x = 0.6 system than x = 0.4 near room temperature.

Resistive Switching and Redox Process at the BaTiO3/(La,Sr)MnO3 Multiferroic‐Type Interface

AbstractResistive switching in oxide‐based structures is intensively studied for the development of ultra‐fast non‐volatile memories with low consumption and neuromorphic electronic devices. Here, evidence of interface‐controlled, reversible, bi‐polar resistance switch in prototype multiferroic BaTiO3/La0.75Sr0.25MnO3 (BTO/LSMO) system is given. The analysis of current–voltage hysteresis curves of a thick Au/BTO/LSMO structure reveals the existence of a 2.55 nm‐thick barrier layer at the bottom BTO/LSMO interface, leading to a tunnel electroresistance of ≈1700%. In the native state where BTO polarization points downward, high resolution electron microscopy and electron energy loss spectroscopy show Ba/(La,Sr) and Ti/Mn cationic intermixing, together with a valency reduction of Mn cations and an oxygen deficiency at the interface. This results in a high resistance state, due to partial loss of the metallicity and of the double exchange magnetic interaction in the oxygen‐deficient LSMO. The switch to the low resistance state, achieved by upward electric field, is explained in terms of re‐oxydation of Mn cations at the interface (decrease of the Mn3+/Mn4+ ratio), with oxygen vacancies migration from LSMO to BTO. This work emphasizes the crucial role of ionic exchanges and of redox processes at interfaces, both on ferroelectric bound charge screening and on resistive switching.

Dynamic observation of manganese adatom mobility at perovskite oxide catalyst interfaces with water

Real time in-situ microscopy imaging of surface structure and atom dynamics of heterogeneous catalysts is an important step for understanding reaction mechanisms. Here, using in-situ environmental transmission electron microscopy (ETEM), we directly visualize surface atom dynamics at manganite perovskite catalyst surfaces for oxygen evolution reaction (OER), which are ≥20 times faster in water than in other ambients. Comparing (001) surfaces of La0.6Sr0.4MnO3 and Pr0.67Ca0.33MnO3 with similar initial manganese valence state and OER activity, but very different OER stability, allows us to distinguish between reversible surface adatom dynamics and irreversible surface defect chemical reactions. We observe enhanced reversible manganese adatom dynamics due to partial solvation in adsorbed water for the highly active and stable La0.6Sr0.4MnO3 system, suggesting that aspects of homogeneous catalysis must be included for understanding the OER mechanism in heterogeneous catalysis.

Effect of Process Control Reagents on Structure and Electrochemical Performance of La0.8Sr0.2MnO3

AbstractIn the present work, well‐recognized La0.8Sr0.2MnO3 (LSM) system as cathode for IT‐SOFC is prepared by using different process control reagents (PCAs) such as stearic acid and salicylic acid with varying grinding times. This is the first attempt to develop LSM by using PCAs in mechanochemical synthesis. By using stearic acid single cubic phase, LSM material is obtained at 3 h of grinding (LSM‐St). However in case of salicylic acid, the respective phase of La0.8Sr0.2MnO3 is achieved for 5 h of grinding (LSM‐Sa) and without PCA the same phase is obtained for 7 h of grinding (LSM‐Wt). X‐Ray diffraction confirms single crystalline cubic phase of as‐synthesized LSM by PCAs and without PCA. All the samples are sintered at 700 °C to improve the degree of crystallinity. Scanning electron microscopy images of as‐synthesized samples reveal highly agglomerate fine‐scale grains. The temperature dependence of direct current conductivity curve exhibits linear dependence of conductivity with temperature, which is found maximum for LSM‐St as compared to other two samples. Symmetric cells in the configuration given by—composite cathode/electrolyte/composite cathode—are fabricated using spin coating technique. The area specific resistance is minimum for LSM‐St based symmetric cell and correlated with the maximum conductivity.

Assessment of structural, optical, magnetic, magnetocaloric properties and critical phenomena of La0.57Nd0.1Sr0.18Ag0.15MnO3 system at room temperature

In this research paper, our central focus is upon structural, optic, magnetic, magnetocaloric, and critical phenomena of La0.57Nd0.1Sr0.18Ag0.15MnO3 (LNSMAO) compound. This compound is crystallized in the rhombohedric system, with a $$R\mathop 3\limits^{ - } c$$ space group. The band gap energy of this powder was 2.5 eV. Therefore, the LNSAMO sample proved to be not only a photocatalysis material but also a photovoltaic application. The FTIR spectra confirmed the formation of the structure of orthorhombic perovskite. The second-order transition of the magnetic phase in the LNSMAO sample was also reported by the positive slopes of the Arrott plot. Beneath 5 T, the values of magnetic entropy change and relative cooling power, respectively, amounted to about 5.08 J kg−1 K−1 and 146.7 J/Kg. In perspective, this sample stands for an agreeable candidate for magnetic refrigeration. By analyzing the dependence on the field of the magnetic entropy change (ΔSM) data as well as the relative cooling power (RCP), it was possible to assess the values of the critical exponents. Moreover, the critical exponents of LNSMAO compound were estimated based on multiple techniques like Kouvel-Fisher (KF), modified Arrott plot (MAP) method, and critical isotherm analysis (CIA). The reliability of these critical behaviors was verified by the Widom scaling relation and the universal scaling hypothesis. Our results demonstrate an excellent correlation between magnetocaloric effect (MCE) properties in manganese systems and critical behavior.

Enhancement of temperature coefficient of resistance (TCR) and magnetoresistance (MR) of La0.67–xRExCa0.33MnO3 (x = 0, 0.1; RE = Gd, Nd, Sm) system via rare-earth substitution

We investigated the influence of 10% substitution of rare-earth (RE) elements on the crystallographic, transport, and magnetic properties of La0.67–xRExCa0.33MnO3(RE = Nd, Sm, and Gd, x = 0.0, 0.1) manganite perovskite compounds. The bulk polycrystalline samples were synthesized using solid-state reaction method. The phase purity and crystal structure of studied samples were confirmed by room temperature X-ray diffraction followed by the Rietveld refinement analysis. A high temperature insulator to low temperature metal phase transition is observed in electrical transport measurement. We observed an enhancement in the temperature coefficient of resistance (TCR) and magnetoresistance (MR) by partially substituting La with RE ions. The maximum TCR ≈ 22% and MR ≈ 96% are observed in Gd doped sample. The magnetic transition temperature, Tc, decreases from ∼254 K for the pristine sample to about ∼165 K for the Gd-doped sample. Our analysis of electrical and thermal transport data shows that the Small Polaron Hopping (SPH) is predominant at high temperatures conduction mechanism, whereas at low temperatures mechanism is dominated by electron-magnon scattering. The high temperature insulator paramagnetic phase to low temperature metallic ferromagnetic phase transitions are also observed in thermal conductivity and specific heat.

Structural study and large magnetocaloric entropy change at room temperature of La1-x □ x MnO3 compounds.

In this study, our central focus is to investigate the magnetocaloric characteristics of a La1−x□xMnO3 (x = 0.1, 0.2 and 0.3) series prepared by a sol–gel technique published in Prog. Mater. Sci., 93, 2018, 112–232. The crystallographic study revealed that our compounds crystallize in a rhombohedral structure with R3̄c. Ferromagnetic (FM) and paramagnetic (PM) characters were detected from the variation in magnetization as a function of magnetic fields at different temperatures. The second order transition was verified from the Arrott plots (M2vs. (μ0H/M)), where the slopes have a positive value. In order to verify the second order, we traced the variation of magnetization vs. temperature at different magnetic fields for x = 0.2. This revealed a ferromagnetic (FM)–paramagnetic (PM) transition when temperature increases. Relying on the indirect method while using the Maxwell formula, we determined the variation in the entropy (−ΔSM) as a function of temperature for different magnetic fields for the three samples. We note that all the studied systems stand as good candidates for magnetic refrigeration with relative cooling power (RCP) values of around 131.4, 83.38 and 57.26 J kg−1 with magnetic fields below 2 T, respectively. Subsequently, the magnetocaloric effect was investigated by a phenomenological model for x = 0.2. The extracted data confirm that this phenomenological model is appropriate for the prediction of magnetocaloric properties. The study also demonstrated that this La0.8□0.2MnO3 system exhibits a universal behaviour.

Magnetocaloric behavior of chromium doped Pr0.5Sr0.5MnO3 system

The magnetocaloric behavior of chromium doped Pr0.5Sr0.5MnO3 manganite system has been studied by synthesizing a series of samples using the citrate sol–gel route. The samples were characterized structurally by XRD and found to be crystallized in orthorhombic structure with Pnma space group. A systematic investigation of magnetization over a temperature range 80–300 K was carried out mainly to understand their magnetic behavior and the transition temperatures are found to decrease with increase in chromium concentration. This may be due to change in Mn3+ and Mn4+ ratio. Further, from the fittings (using a theoretical model) of M-T data at 500 Oestered magnetic field, curie constant has been calculated. It has been observed that due to chromium doping ferromagnetic phases were induced in the charge ordered system and this gave rise to interesting phenomena.

Sintering temperature effects on some physical properties of a Dy0.5(Sr/Ca)0.5MnO3 system

A Dy0.5(Sr0.95Ca0.05)0.5MnO3 system has been prepared by the sol gel method and sintered at temperatures of 700 °C and 1350 °C for a similar period of time. Its electrical and dielectrical data as a function of frequency and temperature have been recorded by means of impedance spectroscopy. It is observed that the contribution of grain boundary to total resistance becomes dominant once increasing sintering temperature. The increase of sintering temperature increases the static dielectric constant by 25 times. Such interesting result is understood in the framework of many reasons including the presence of oxygen vacancies. Unlike sample sintered at 700 °C , the compound sintered at 1350 °C reveals two extra relaxation processes. Further, the sample sintered at 1350 °C possesses the higher value of the dielectric constant as well as a lower value of the loss tangent, which makes it a promising candidate for technological applications. For transport properties, the conduction process is found to be governed by the band gap model.

Magnetic Entropy Change in La0.57Nd0.1Sr0.13Ag0.2MnO3 by Means of Theoretical Models

In the present research work, a phenomenological model is applied to describe the magnetocaloric effect of the La0.57Nd0.1Sr0.13Ag0.2MnO3 system near a second-order phase transition from ferromagnetic to paramagnetic state. Based on this model, the values of the magnetocaloric properties are predicted from the calculation of magnetization as a function of temperature under different external magnetic fields. The maximum magnetic entropy change ( $$ - \Delta S_{\text{M}}^{\mathrm{max} } $$ ) and the relative cooling power are found to be, respectively, 1.51 J kg−1 K−1 and 71.96 J kg−1 for H = 2T, making this material a suitable candidate for magnetic refrigeration applications. The magnetic entropy change ΔS has been determined using the Landau theory consistent with the experimental ones. A master curve of the magnetic entropy change confirmed the second order of the magnetic phase transition.

Tuning magnetic and magnetocaloric properties around room temperature via chromium substitution in La0.65Nd0.05Ba0.3MnO3 system

Abstract In this paper, we report the structural, magnetic and magnetocaloric properties of La0.65Nd0.05Ba0.3Mn1−xCrxO3 (0 ≤ x ≤ 0.15) system synthesized by conventional solid-state reaction method. Phase identification is performed by X-ray diffraction analysis, which shows the rhombohedra crystal structure with R -3 c as a space group. Magnetic measurements show that all our samples undergo a second order paramagnetic (PM) – ferromagnetic (FM) transition when the temperature decreases. However, The M(T) shows a decrease in a Curie temperature (TC) from 330 K for x = 0 to 275 K for x = 0.15 as a Cr ion increases. This decrease can be explained by the decreasing number of hopping electrons, which reduces the double exchange (DE) interaction of Mn3+-O-Mn4+. The role of the trivalent ions Cr3+ is merely to dilute the DE interactions between Mn sites. Moreover, the maximum magnetic entropy change −ΔSM calculated from the M(μ0H) measurements are found to be 4.26, 4.03, 3.97 and 3.55 Jkg−1K−1 under an external field change of 5 T for x = 0, 0.05, 0.1 and 0.15, respectively. However, the temperature-averaged entropy change (TEC) over 10 K temperature span under same field, TEC (10 K, 5 T), are 4.19, 3.91, 3.86 and 3.47 Jkg−1K−1. This finding suggests that our samples can be used as a magnetic refrigeration material around room temperature. Furthermore, the ΔSM –T curves collapse onto a single master curve confirming the second order phase transition. Additionally, a phenomenological universal model is used to predict the magnetocaloric properties for Cr substituted samples.