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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]

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]

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]

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]

Complex oxide thin films exhibit intriguing phenomena due to the coupling between multiple degrees of freedom through interfacial structural engineering. Atomic tailoring of structural parameters determines unique band structure and phonon modes, regulating emergent magnetic and electrical properties of oxide films. However, the construction of different strained and oriented domains in one intact oxide thin film is impossible using conventional means. Here we report the fabrication and quantitative structural analysis of La0.7Sr0.3MnO3 (LSMO) homostructures assisted by atomic-flat freestanding membranes. Pristine substrates and suspended membranes regulate the epitaxial strain and orientation of subsequently grown films. Our results demonstrate an ultrathin transition layer (∼ 4 atomic layers) between freestanding membranes and LSMO films is formed due to the strain relaxation. This work offers a simple and scalable methodology for fabricating unprecedented innovative functional oxide homostructures through artificially controlled synthesis routes. [ABSTRACT FROM AUTHOR]

In this study, the effect of Ru additive on the crystallographic, magnetic, and electrocatalytic properties of LaBiBaMnO 3 manganite was investigated for magnetic refrigeration and energy storage systems. XRD analysis of La 0·62 Bi 0·05 Ba 0·33 MnO 3 (LBBM) and La 0·62 Bi 0·05 Ba 0·33 Mn 0·90 Ru 0·10 O 3 (LBBMR) manganites prepared by solid state method reveals that the samples have a rhombohedral structure and the average grain size of perovskites are found to be below 3 μm. From the temperature-dependent magnetization measurements, it was observed that the value of Curie temperature (T C) decreased from 334 K for LBBM to 327 K for LBBMR with the substitution of Mn with 10% Ru. In parallel with the decrease observed in T C with Ru contribution, a decrease in magnetic entropy value was also observed. The substitution of 10% Ru reduced the onset potential 51 mV for oxygen evolution reaction (OER) and 74 mV for oxygen reduction reaction (ORR). The electrode activity of OER at 10 mA cm−2 was obtained at around 0.976 V. Ru substitution and increasing scan rate to 100 mV s−1 increased the current density and lowered onset potential for OER. The ORR efficiency of LBBM catalysts boosted up to 60% with the durability test for 6 h. The increased cathodic Tafel slope from −255.1 mV dec−1 to −120.4 mV dec−1 with 10% Ru substitution suggests that a fast charge transfer for ORR activity due to Ru-occupied Mn-sites in the structure. LBBMR sample achieved bifunctional properties as ORR/OER performance and magnetic cooling applications by substituting Mn with 10% Ru. • The effect of Ru additive on the magnetic and electrocatalytic properties of LaBaBiMnO 3 manganite was investigated. • T c temperatures are determined as 334 K for LBBM and 327 K for LBBMR. • The addition of 10% Ru reduced the onset potential 51 mV for OER and 74 mV for ORR. • Anodic and cathodic slopes were improved to −74.2 mV dec−1 and 92 mV dec−1 with the addition of 10% Ru for ORR/OER. • Replacing of 10% Ru in LBBMR catalyst kept its 60% efficiency up to 6 h while RuO 2 exhibited 90% efficiency. [ABSTRACT FROM AUTHOR]

Several phase separated manganites present a peculiar effect each time they go through a phase transition within the range characterized by phase separation. The effect is known as the thermal cycling effect (TCE) and is characterized by monotonous changes in the relative content of the coexisting phases. In this work, we analyze a way to control the effects induced by TCE, performing thermal treatments at high temperature. Our results revealed a complex interplay between the dynamic and static characteristics of the phase separated state, which can be analyzed in terms of three simple parameters. One related to the static properties, another to the dynamic properties and a last one that acts as a link between both features. [ABSTRACT FROM AUTHOR]

Among transition metal oxides, manganites have attracted significant attention because of colossal magnetoresistance (CMR)—a magnetic field-induced metal–insulator transition close to the Curie temperature. CMR is closely related to the ferromagnetic (FM) metallic phase which strongly competes with the antiferromagnetic (AFM) charge ordered (CO) phase, where conducting electrons localize and create a long range order giving rise to insulator-like behavior. One of the major open questions in manganites is the exact origin of this insulating behavior. Here we report a dc resistivity and magnetization study on manganite La 1 − x Ca x MnO 3 ceramic samples with different grain size, at the very boundary between CO/AFM insulating and FM metallic phases x = 0.5 . Clear signatures of variable range hopping (VRH) are discerned in resistivity, implying the disorder-induced (Anderson) localization of conducting electrons. A significant increase of disorder associated with the reduction in grain size, however, pushes the system in the opposite direction from the Anderson localization scenario, resulting in a drastic decrease of resistivity, collapse of the VRH, suppression of the CO/AFM phase and growth of an FM contribution. These contradictory results are interpreted within the standard core-shell model and recent theories of Anderson localization of interacting particles. [ABSTRACT FROM AUTHOR]

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

We have investigated the influence of the disorder on the resistive relaxation effects in the Sm1-aSraMnO3 system where a is the fraction of the alkaline element. The disorder was introduced through chemical substitution of Mn sites with Fe doping, Ru doping, or forming composite structures by adding small fractions of BaTiO3. These three routes of adding disorder lead to a distinct behavior of Tc and TMIT that depends on the concentrations and types of dopants. All the samples with a measurable zero-field resistive relaxation effect exhibited two peaks in the temperature dependence of the relaxation rates. In particular, a negative peak is found at low temperatures near the onset temperature of anti-ferromagnetic ordering while a positive peak is found near the metal–insulator transition temperature. In an attempt to quantify the strength of the disorder, we have determined the ΔT for each sample where ΔT is defined as the difference in the metal–insulator transition temperature (TMIT) obtained from the warming and cooling curves in the temperature dependence of the resistivity. The magnitudes of the peaks increase in an exponential-like manner with the increasing thermal hysteresis width ΔT, which is a measure of the extent of the inhomogeneous magnetic state or disorder in the manganite system. On the other hand, the Ru substitution of Sm1-aSraMnO3 (SGSMO) reduced the thermal hysteresis width ΔT substantially and subsequently the relaxation rates. Our observations revealed a clear relationship between the quenched disorder and the resistive metastability in manganites. [ABSTRACT FROM AUTHOR]

In insulating compounds R1-xAxMnO3, the role of orbital ordering in magnetic competition is emphasized. The conditions of ordered state's destruction are estimated. The ranges of orbital structure mixing angles to form frustrated or low-dimensional magnetic structures are determined. The influence of nonlinear and nonlocal terms of vibronic interaction on orbital ordering and magnetic structure are discussed. The possible magnetic structures are described. [ABSTRACT FROM AUTHOR]

[Display omitted] • The rhombohedral La 0.8 K 0.2-x Li x MnO 3 (0 ≤ x ≤ 0.075) samples were synthesized using the sol–gel technique at low temperature. • All the samples exhibit a second order paramagnetic-ferromagnetic transition with decreasing temperature. • Δ S M Max under an applied magnetic field change of 5 T is found to be 3.19, 3.51, 2.39 and 2.24 J kg−1 K−1 for x = 0, 0.025, 0.05 and 0.075 respectively • The RCP (S) of La 0.8 K 0.175 Li 0.025 MnO 3 sample is 320.5 J/kg under a magnetic field change of 5 T. In this study we report the effect of lithium substitution on the structural, magnetic and magnetocaloric properties of La 0.8 K 0.2-x Li x MnO 3 (0 ≤ x ≤ 0.075) samples synthesized by the sol–gel technique at low temperature. The investigated compounds crystallize in a rhombohedral system with R 3 ¯ c space group. The thermal variation of the magnetization under an applied magnetic field of 0.05 T showed that all our compounds exhibited a paramagnetic to ferromagnetic transition with decreasing temperature. With increasing lithium content, the Curie temperature T C , decreases from 287.4 K for x = 0 to 172.6 K for x = 0.075. The maximum of the magnetic entropy change, - Δ S M Max , is found to be 3.19, 3.51, 2.39 and 2.24 J kg−1 K−1 in a magnetic field change of 5 T for x = 0, 0.025, 0.05 and 0.075 respectively. The La 0.8 K 0.175 Li 0.025 MnO 3 sample displays a higher maximum relative cooling power value of 320.5 J kg−1, equal to 78 % of that of gadolinium. Technically, this large value associated to a T C of 270 K makes the present sample very promising for magnetic refrigeration technology below room temperature. [ABSTRACT FROM AUTHOR]

Structural analysis, magnetocaloric properties, and theoretical investigations of the magnetocaloric effect were carried out in the crystalline La0.7Ba0.15Ag0.15MnO3 manganite prepared using sol-gel route. The phase purity and structure of this sample were checked by X-ray diffraction technique and Rietveld analysis. From magnetic measurements, the ferromagnetic to paramagnetic (FM-PM) phase transition was observed around TC = 255 K. The maximum change in magnetic entropy (∆ S M max ) and relative cooling power (RCP) extracted from magnetic measurements were 3.48 J × kg-1 × K-1 and 225 J × kg-1 at an applied magnetic field of 5 T. These magnetocaloric parameters offer to the sample the possible use in the magnetic refrigeration technology. The magnetic entropy simulation by using different theories such as the Weiss molecular mean-field theory and the Landau theory shows good correlation between the theoretical values of −∆SM(T) and the experimental ones estimated from Maxwell relation. [ABSTRACT FROM AUTHOR]

We have reported the solgel synthesis, the structural analysis, and the correlation between magnetic and electrical properties of La0.7Ba0.15Ag0.15MnO3 manganite. The phase purity and structure of this sample were checked by X-ray diffraction technique and Rietveld analysis. M(T) measurement shows a ferromagnetic (FM)-to-paramagnetic (PM) phase transition of second-order type at Curie temperature TC = 255 K. The obtained magnetocaloric parameters offer to the sample the possible use in the magnetic refrigeration technology. The resistivity data, ρ(μ0H, T), show the presence of metal–semiconductor transition and a maximum magnetoresistance (MR) value of the order of 32% at magnetic field of 5 T. The phenomenological percolation model was used to study the conduction mechanism of the sample. It has been also shown that, from analyzing the temperature and magnetic field dependences of the electrical resistivity, it is possible to predict the behavior of the magnetization as well as the change of magnetic entropy near the phase transition temperature. The obtained agreement with experimental data for this analysis is quite reasonable. [ABSTRACT FROM AUTHOR]

In this work, an overview of the Weiss molecular mean-field theory, the Bean–Rodbell model and the Landau theory is presented, providing the theoretical background for simulating the magnetocaloric properties for La0.6Ca0.2Na0.2MnO3 manganite. Results showed that sample exhibits second-order ferromagnetic (FM)–paramagnetic (PM) magnetic phase transition and relatively higher values of magnetic entropy change (−∆SM). In application point of view, this material can be used in magnetic refrigeration technology. The theoretical values of −∆SM determined using each theory agree well with the experimental ones estimated from Maxwell relations. In other part, a good agreement in the spontaneous magnetization values, Mspont(T), estimated from (−∆SM vs. M2) and (H/M vs. M2) data was found. Also, the values of the critical exponent (β) found from both methods are close and check that the mean-field model is adequate to study the MCE in La0.6Ca0.2Na0.2MnO3 sample. [ABSTRACT FROM AUTHOR]

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

The high-energy ball milling method has been used to synthesize the polycrystalline powders La0.5Ca0.5Mn1−xVxO3 (x = 0.05, x = 0.10). The Rietveld refinement technique shows that the samples crystallized in the orthorhombic structure with the Pbnm space group. The La0.5Ca0.5Mn0.95V0.05O3 exhibits a second-order phase transition from paramagnetic (PM) to ferromagnetic (FM) state at TC = 208 ± 1 K followed by a second one from FM to charge ordering–antiferromagnetic state at TN = 150.0 ± 0.1 K when decreasing temperature. The substituted sample with 10% amount of vanadium dopant corresponds to the disappearance of the charge-order phase; meanwhile, it was suppressed for 5% of the vanadium in the solid-state route. The Curie temperature TC increases with vanadium content from 208 ± 1 K for x = 0.05 to 255 ± 1 K for x = 0.10. The values of the maximum of the magnetic entropy change under a magnetic field change of 5 T are found to be 2.95 ± 0.04 J kg−1 K−1 and 5.42 ± 0.07 J kg−1 K−1 corresponding to a relative cooling power RCP = 128.4 ± 0.3 and 220.8 ± 0.7 for x = 0.05 and x = 0.10 respectively. The order of phase transition has been determined. The critical exponent study has been performed for La0.5Ca0.5Mn0.9V0.10O3 by using the Arrott plot, Kouvel–Fisher method, and critical isotherm analysis. The measured β, γ, and δ values are in agreement with those expected for the tricritical mean-field model. [ABSTRACT FROM AUTHOR]

Electronic phase separation in complex oxides is the inhomogeneous spatial distribution of electronic phases, involving length scales much larger than those of structural defects or nonuniform distribution of chemical dopants. While experimental efforts focused on phase separation and established its correlation with nonlinear responses under external stimuli, it remains controversial whether phase separation requires quenched disorder for its realization. Early theory predicted that if perfectly "clean" samples could be grown, both phase separation and nonlinearities would be replaced by a bicritical-like phase diagram. Here, using a layer-by-layer superlattice growth technique we fabricate a fully chemically ordered "tricolor" manganite superlattice, and compare its properties with those of isovalent alloyed manganite films. Remarkably, the fully ordered manganite does not exhibit phase separation, while its presence is pronounced in the alloy. This suggests that chemical-dopinginduced disorder is crucial to stabilize the potentially useful nonlinear responses of manganites, as theory predicted. [ABSTRACT FROM AUTHOR]

The influence of lead substitution on the magnetocaloric properties of La0.7(Te1-xPbx)0.3MnO3 (0.0 ≤ x ≤ 0.3) manganites synthesized by solid-state reaction process was studied both by experimental and theoretical modeling. The X-ray diffraction patterns reveal that samples crystallize in the rhombohedral perovskite structure. Thermomagnetic measurements indicate that the magnetic transition temperature increases gradually from 238 to 262 K with increasing Pb amount in the structure. Maximum magnetic entropy changes (ΔSM) are determined to be 7.16 for x = 0.0 and 4.76 J kg−1 K−1 for x = 0.3. Relative cooling power (RCP) values of samples are ranging between 266.94 and 195.21 J kg−1 at ΔH = 5 T. Due to relatively high ΔSM and RCP values of the samples, they can be potential materials in magnetic refrigeration applications which work around room temperature. [ABSTRACT FROM AUTHOR]

Meyer-Neldel behaviour of the conductivity of phase separated La1−xCaxMnO3 manganite system in the low Ca-doping range has been investigated. Evolution of the isokinetic temperature of the conductivity, modified by Ca-doping, hydrostatic pressure and current bias has been determined. In addition, the evolution of the isokinetic temperature with ageing has also been studied. It is found that the Meyer-Neldel behaviour of the manganite system stems from multi-excitation entropy mechanism. The isokinetic temperatures estimated from pressure and doping effects coincide but differ from those determined using current and ageing controlled conductivity changes. It is concluded that in the presence of a detailed theoretical model of the excitations coupling in manganites, the investigations of the Meyer-Neldel effect may became a powerful tool for characterization and investigation of transport mechanisms in phase separated manganites. [ABSTRACT FROM AUTHOR]

The critical behavior of La 0.5 Ca 0.2 Sr 0.3 MnO 3 manganite has been investigated by measuring the magnetization around the Curie temperature T C . The experimental results indicate that this sample exhibits a second-order phase transition. The critical exponents (β , γ and δ ) are estimated using the Kouvel–Fisher technique and critical isotherm analysis. The reliability of obtained exponents was confirmed by using the universal scaling hypothesis. The obtained β value ( = 0.47 ) is close to that expected for the mean-field model ( = 0.5 ), while the γ value ( = 1.28 ) lies between the 3D Ising ( = 1.24 ) and 3D Heisenberg ( = 1.336 ) models. This reveals that the critical exponents of this half-doped manganite do not correspond to the conventional universality classes. In addition, the results show that the ferromagnetic interaction is of itinerant type. [ABSTRACT FROM AUTHOR]

We summarize the long-term electron transport and electronic noise investigations of low-doped La 0. 8 6 Ca 0. 1 4 MnO3 manganite single crystal being in its several, consecutive metastable resistivity states: the pristine high-resistivity one, the low-resistivity, and finally in the high-resistivity metastable state. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and magnetocaloric effect (MCE) properties and the critical behavior of the La0.45Pr0.2Sr0.35MnO3 sample prepared by the sol–gel method have been investigated. The X-ray diffraction characterization reveals that our sample crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature measurement shows that our compound exhibits a ferromagnetic–paramagnetic transition. The Curie temperature is found to be 348 K. Close to this temperature, the maximum values of the magnetic entropy change (ΔSM) and the relative cooling power (RCP) are found to be 2.84 J/kg/K and 230 J/K under µ0H = 5 T, respectively. The Arrott plots revealed that this compound exhibits a second-order magnetic phase transition at TC. The critical behavior has been investigated by several techniques which are the modified Arrott plot method, the Kouvel–Fisher method, and the critical isotherm analysis. The obtained critical exponents β, γ, and δ are consistent with those predictions of the mean-field model. Their reliability was confirmed by Widom's scaling relation, as well as the universal scaling hypothesis. [ABSTRACT FROM AUTHOR]

Abstract We report on the structural, magnetic and transport properties of the Pr-doped manganite (La 1- x Pr x) 0.7 Ba 0.3 MnO 3 (x = 0.05 and 0.15). X-ray diffraction data demonstrate that both samples possess dual crystallographic phases: rhombohedral R 3 ¯ c and orthorhombic Pnma. This is due to the martensitic phase transition inherent to the pristine La 0.7 Ba 0.3 MnO 3 sample, whose impact is seen as a second metal-insulator (MI) transition below the ordered temperature in electric measurements. Griffiths phase (GP)-like behavior in the inverse magnetic susceptibility (χ−1(T)) was observed only for Pr -15%. The origin of the Griffiths singularity could be understood in terms of the competing accommodation strain arising from martensite-like phase transition and quenched disorder. Interestingly, GP cannot be considered as a precursor for the magnetoresistance (MR), but can be essential for improving the temperature coefficient of resistance (TCR). At low temperature, the magnetization follows the Bloch's T 3/2 law, while the resistivity shows a shallow minimum in both samples. Our work reveals that, at low temperature, the influence of the magnetic contribution of Pr3+ becomes relevant against the quenched disorder (σ 2). These findings suggest that quenched disorder, strain field, and the coupling between rare-earth and Mn3+/Mn4+ sublattice are important factors in determining the structural and magneto-transport properties in manganite systems. Graphical abstract Image 1 Highlights • Quenched disorder destroys the martensitic transition. • Two metal–insulator transitions are detected in the electrical resistivity. • Griffiths singularity improve the temperature coefficient of resistance. • A shallow minimum has been observed at low temperature resistivity. [ABSTRACT FROM AUTHOR]

Highlights • Magneto-caloric properties of manganite La 0.6-x Gd x Sr 0.4 MnO 3 (x = 0, 0.0125, 0.05, 0.10) was investigated. • Rietveld refinement analysis indicated that the gradual replacement of La with Gd effect. • Magnetization measurements as a function of temperature on all the samples showed a ferromagnetic transition change. • Magneto-caloric parameters measurements suggested the samples for the magnetic refrigeration application. Abstract The effect of slight changes of the chemical composition on Magneto-caloric properties of manganite was investigated on a series of ceramic nano-particles of La 0.6-x Gd x Sr 0.4 MnO 3 (x = 0, 0.0125, 0.05, 0.10) where they synthesized using the Sol-gel method. The X-ray powder diffraction data and the Rietveld refinement analysis indicated that the gradual replacement of La with Gd reduced the cell volume acting in a comparable manner to applying external pressure. Similarly, the magnetization measurements as a function of temperature on all La 0.6-x Gd x Sr 0.4 MnO 3 samples showed a ferromagnetic transition, in which the transition temperature reduced as x increased. The calculated magnetic entropies of all samples of La 0.6-x Gd x Sr 0.4 MnO 3 as a function of temperature suggest a magneto-caloric effect similar to that of pure Gd. These results provide evidence that La 0.6-x Gd x Sr 0.4 MnO 3 compounds have a potential for magnetic refrigeration application. [ABSTRACT FROM AUTHOR]

The critical exponents and magnetocaloric properties of La0.7Sr0.3Mn1−xTixO3 with x = 0 and 0.05 have been explored via magnetic measurements. The magnetic data analyzed in the critical region by using modified Arrott plots, the Kouvel-Fisher method, and the scaling hypothesis reveal values for the critical parameters of β = 0.3165 and 0.3027, γ = 1.1121 and 1.203, and δ = 4.7556 and 4.833 for x = 0 and x = 0.05 respectively. These values are in agreement with the three-dimensional (3D) Ising model. The n values obtained from the law ΔSmax=a(μ0H)n are 0.648 and 0.685. The maximum values of the magnetic entropy change are 1.65 J/kg K and 1.46 J/kg K under a magnetic field change of 10 kOe for x = 0.00 and 0.05, respectively. These results can be explained in the scenario of the short-range interaction and the phase separation as well as the diluted magnetic effect in manganites. [ABSTRACT FROM AUTHOR]

Abstract In this communication, low resistive bulk La 0.7 Ca 0.3 MnO 3 (LCMO) was prepared by solid state reaction (SSR) route whereas high resistive nanoparticles of LaMnO 3 (LMO) was prepared by cost effective sol–gel technique. Composites of LMO and LCMO were prepared by mixing them in different weight ratios, i.e. LMO = 10%, 20% and 30% in LCMO manganite matrix. In the present study, LMO have been used as nanoparticle fillers in the LCMO matrix lattice to study the transport properties of the composites. X–ray diffraction (XRD) measurement reveals the single phasic nature of the composites without any detectable impurity within the measurement range studied. XRD pattern of higher LMO content based composite possesses slightly different structural phases of LMO and LCMO. Resistivity measurement reveals that all the composites exhibit metal to insulator electronic phase transition at respective T P , wherein values of resistivity and T P get modified due to the cooling or heating cycles performed, measurement current used and LMO nanoparticle filler content in the composites. These variations have been discussed in the context of scattering centres created due to the presence of LMO fillers and complex phase separation scenario of the composites. A clear phase separation in higher filler content based composite has been displayed in its resistivity behaviour. To understand the charge transport mechanisms responsible for metallic and insulating (or semiconducting) regions in resistivity behaviours of the composites, most suitable zener double exchange polynomial law and Mott type variable range hopping mechanism were fitted theoretically to the obtained experimental results. Fittings show that spin fluctuations in the composites are highly dependent on the cycles performed, current applied and LMO nanoparticle filler content in the composites. Applied negative and positive current and voltage dependent resistance of the composites reveal the negative electroresistance. Both, resistance of the composites as well as electroresistance are highly affected by the cycles performed, current applied and LMO nanoparticle filler content in the composites understudy. Temperature dependent electroresistance was studied for better insight into an active role of phase separation near electronic phase transition temperatures for all manganite based composites. Graphical abstract Image 1 Highlights • Transport properties of manganite–manganite composites. • Preparation of single phasic manganite metallic matrix using ceramic method. • Synthesis of nanostructured manganite fillers using sol–gel technique. • Role of complex phase separation scenario in charge conduction mechanisms. [ABSTRACT FROM AUTHOR]

La0.7Sr0.3MnO3 (LSMO) and La0.7Ba0.3MnO3 (LBMO) Polycrystalline manganite nanoparticles were prepared by combustion method using glycine fuel. The ignition process was done at 360 °C and 330 °C for LSMO and LBMO, respectively. Both of the samples have rhombohedral structure using XRD analysis. The reduction is observed in electrical resistivity when external magnetic field is applied during the decrease in temperature from 300 to 89 °K, which is due to the tunneling between particles. The magnetoresistance (MR) of samples was measured in this range of temperature in both the presence and absence of a magnetic field of about 10 kG. The colossal role of a kind of extrinsic MR which is 19% and 22% for LSMO and LBMO, respectively, has been investigated in this research. The metal-insulator transition temperature of 200 °K is recorded for LBMO. [ABSTRACT FROM AUTHOR]

We have performed a systematic study of the critical properties of Pr 0.8 K 0.2 MnO 3 manganite synthesized using two various methods in the vicinity of the ferromagnetic–paramagnetic phase transition. Our compound was successfully prepared by using the solid state reaction at high temperatures and Pechini sol-gel method. The X-ray diffraction pattern shows that all our samples adopt an orthorhombic structure with Pnma space group. Moreover , the critical exponents β, γ and δ are estimated through various techniques such as the modified Arrott plot, the Kouvel–Fisher method and the critical isotherm analysis founded on the data of the magnetic measurements on record near the Curie temperature. Compared to standard models, the estimated critical exponents are close to the theoretical values of 3D-Heisenberg model for the sample elaborated by solid state reaction and tricritical mean-field model for the sample elaborated by the sol-gel method. These results indicate the presence of a ferromagnetic short-range order in our samples. The calculated values using the Widom scaling equation are proximate to those obtained values from critical isotherm M (T C , µ 0 H). The accuracy of the critical exponents values was confirmed with the scaling hypothesis, the magnetization curves fall onto two sides independents below and above T C . Interestingly, the change of the universality class is due to the relevant the diminution of grain size. These results imply that the critical behavior of our samples depended sorely on the synthesis technique. [ABSTRACT FROM AUTHOR]

Highlights • The uniform model of orbital structure is presented. • The most important application is the case of magnetic frustration. • The orbital-magnetic structures phase diagrams are drawn. Abstract In insulating manganites, a semi-empirical model of orbital structure is proposed. The model allows us to account for the non-linear and non-local effects of a crystal structure on the orbital ordering of a trivalent manganese sublattice. This allows the variation of only two parameters for each degenerated manganese ion. They include the main part – the linear vibronic interaction – and additional parts (as long-range Coulomb fields or non-linear vibronic interactions). This is why one can define the orbital structure with respect of the magnetic structure without explicit microscopic definition of the non-linear and non-local terms. The continuous changes to the orbital mixing parameters are important for magnetic structure description. Within the framework of orbitally-dependent superexchange interaction, magnetic structures dependent on orbital orderings are considered. For manganite crystals LaMnO 3 , BiMnO 3 , La 0.5 Ca 0.5 MnO 3 , La 0.333 Ca 0.667 MnO 3 , phase diagrams of the orbital and magnetic structures with an unchanged crystal structure are drawn. The role of orbital ordering in frustrated magnetic structures is emphasized. The insufficiency of the linear vibronic approach is shown. [ABSTRACT FROM AUTHOR]

Abstract In this communication, we report the results of the studies on structural, transport and magnetoresistance (MR) properties of nonmagnetic Ga – substituted La 0.67 Ca 0.33 Mn 1–x Ga x O 3 (LCMGO) manganites synthesized using conventional ceramic route. Rietveld refined XRD patterns shows that all the samples possess single phasic nature without any detectable impurity. Resistivity behavior shows a systematic variation with Ga3+ – content (x) while metal to insulator transition temperature (T P) shifts towards lower temperature which has been discussed in the light of zener double exchange (ZDE) mechanism and magnetic lattice distortion due to nonmagnetic ion substitution. Observation of low temperature resistivity minima behavior has been explained in the context of electron – electron scattering mechanism. Various transport models and mechanisms have been employed to understand the charge transport in metallic and semiconducting regions of all LCMGO samples. Temperature and Field dependent MR studies reveal intrinsic and extrinsic MR contributions in presently studied LCMGO manganites. Highlights • Effect of smaller nonmagnetic Ga3+ doping on charge conduction mechanisms for manganites. • Various models and mechanisms for charge conduction. • Electron–electron scattering mechanism is appropriate for low temperature resistivity minima. • Zener double exchange mechanism responsible for metallic region. • Variable range hopping mechanism for semiconducting region. [ABSTRACT FROM AUTHOR]

In this communication, we present a systematic investigation on structural, electric, magnetic and thermoelectric power properties of REMnO3 (RE = Dy, Gd, Eu and Sm) manganites which were prepared using solid-state reaction route. The samples exhibit orthorhombic crystal structure with Pbnm space group. Rietveld analysis of x-ray diffraction (XRD) data shows that the unit cell volume increases with increase in ionic radii of the rare earth ion, rRE. The particle size was calculated from the scanning electron microscope (SEM) images. The estimated particle size is observed to decrease with increasing ionic radii of the rare earth ions. All samples exhibit insulating behaviour and display immeasurably high resistivity at low temperatures. Magnetization studies indicate that the samples display a transition in the low temperature region. Magnetization data also reveals that antiferromagnetic behaviour is observed for all samples. Thermoelectric power results show that large thermoelectric power is seen for these manganites. Thermoelectric power of high-temperature region was successfully analysed using small polaron hopping (SPH) model. [ABSTRACT FROM AUTHOR]

In this work we address the interplay between two phenomena which are signatures of the out-of-equilibrium state in phase separated manganites: irreversibility against thermal cycling and aging/rejuvenation process. The sample investigated is La 0.5 Ca 0.5 MnO 3 , a prototypical manganite exhibiting phase separation. Two regimes for isothermal relaxation were observed according to the temperature range: for T > 100 K, aging/rejuvenation effects are observed, while for T < 100 K an irreversible aging was found. Our results show that thermal cycles act as a tool to unveil the dynamical behavior of the phase separated state in manganites, revealing the close interplay between static and dynamic properties of phase separated manganites. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect along with magnetic phase transition in the peroveskite polycrystalline samples La 0.7 Ba 0.2 Ca 0.1 Mn 1-x Sn x O 3 (x = 0 and 0.1) was investigated. The samples were synthesized using conventional solid state reaction at 1400 °C temperature. Magnetization vs. temperature measurements, under a magnetic field of μ 0 H = 0.05 T, showed a paramagnetic-ferromagnetic transition at Curie temperature, T C , which decreases from 310 K for x = 0–290 K for x = 0.1. A large magnetic entropy change | Δ S M | deduced from isothermal magnetization curves, has been observed in our samples with a peak centered on their respective T C . Interesting values of the relative cooling power (RCP), 237 J kg -1 for x = 0 and 248 J kg -1 x = 0.1, make these samples promising candidates for magnetic refrigeration around room temperature. [ABSTRACT FROM AUTHOR]

The influence of a magnetic field on reflection and transmission spectra of ferromagnetic manganites possessed the colossal magnetoresistance effect has been in the infrared range studied. It was shown that observed magnetotransmission and magnetoreflection of unpolarized light are an optical response to the colossal magnetoresistance in optimally doped manganites. Compared to crystals and multilayers the effects are the most pronounced and reach the magnitude of up to few tens of percent in single-layer thin films near the Curie temperature. A new low-temperature mechanism of magnetotransmission connected with the tunnel magnetoresistance was revealed far below the Curie point in Ba-doped manganite films with a variant structure. The observed magneto-optical effects in manganites can be described in the framework of the magnetorefractive effect theory. The observed effects are one or two orders of magnitude greater than the conventional IR magnetooptical phenomena in manganites. Being quite large, magnetoreflection and magnetotransmission effects in manganites structures could be successfully used in optoelectronics. [ABSTRACT FROM AUTHOR]

In this work, the effect of Pr doping at the Bi site on the critical behavior and magnetocaloric and transport properties of Bi0.5−xPrxCa0.5MnO3 (0.0 ≤ x ≤ 0.50) manganite synthesized by sol-gel method is reported. An increase in Curie temperature (TC) with an increase in Pr content is observed. The samples with x = 0.0-0.40 show first-order phase transition whereas the sample with x = 0.50 shows second-order phase transition near TC. The estimated values of critical exponents β = 0.75 and γ = 0.82 for the sample with x = 0.50 do not fall into any universality class. The sample with x = 0.50 shows maximum magnetic entropy change (|ΔSm| = (1.22 J kg−1 K−1) at TC in an applied magnetic field of 40 kOe, which is associated with magnetocaloric effect (MCE). All the samples show semiconducting behavior and also follow Mott’s variable range hopping (VRH) model below the charge ordering temperature (TCO). The changes in magnetic and transport properties are correlated with the changes in the structural parameters of the samples. The results are discussed in view of the effect of Pr doping on the 6s2 lone pair character of Bi3+ ions and disorder in the samples. [ABSTRACT FROM AUTHOR]

Polycrystalline Pr 1- x Ca x MnO 3 ( х = 0.3, 0.35, 04, 0.45, and 0.5) samples are synthesized by solid-state reaction method. Crystal structure of the samples is studied by X-ray diffraction method with Rietveld refinement. Diffraction patterns from all the samples are well indexed within the Pnma space group. It is shown that lattice parameters and unit cell volume decrease monotonically and O−Mn−O angles become closer to the ideal 180⁰ value upon the growth of x . Mn2p, Mn3s, Ca2p, Pr3d, Pr4d, and O1s X-ray photoelectron spectra are measured. Pr3d and Pr4d spectra are calculated in isolated ion approximation with approximate accounting for the charge transfer effect. Elemental compositions of samples are measured by the XPS method; they differ noticeably from the nominal ones. Charge compensation upon heterovalent Pr 3+ → Ca 2+ substitution is shown to realize via two mechanisms: creation of oxygen vacancies and formation of Mn 4+ ions coexisting with Mn 3+ . Relative Mn 4+ /Mn 3+ abundances are determined via decomposition of Mn2p and Mn3s XPS into contributions from the spectra of tri- and quadrivalent Mn ions. The amount of Mn 4+ ions is shown to increase with Ca content x . [ABSTRACT FROM AUTHOR]

In the present work, we have investigated the structural, magnetic and magnetocaloric properties of Pr 0.67 Ba 0.22 Sr 0.11 Mn 1-x Fe x O 3 (0 ≤ x ≤ 0.15) manganites oxides. The compounds were elaborated using the conventional solid-state reaction. X-ray diffraction (XRD) at room temperature were used to carry out the structural properties. The magnetic and the magnetocaloric effect properties were explored using magnetization measurements at different parameters such as changing temperature or the applied magnetic field. XRD results indicate that all our compositions crystallized in the orthorhombic structure with Pnma space group. Magnetic measurements as a function of temperature, M (T), under an applied magnetic field of 0.05 T show that all the synthesis compounds present a paramagnetic (PM) – ferromagnetic (FM) transition with decreasing temperature. Arrott plots analysis reveals that our materials exhibit a second order magnetic phase transition. The magnetic entropy change | Δ S M | was calculated using Maxwell relation. The maximum values of the magnetic entropy change ( | Δ S M max | ) for x = 0.00, 0.05, 0.10 and x = 0.15 are found to be 4.72, 1.90, 1.45 and 0.83 J kg −1 K −1 , respectively, which corresponds to relative cooling power (RCP) about 218, 175, 122 and 79 Jkg −1 under a magnetic field change of 5T. [ABSTRACT FROM AUTHOR]

This work presents a study of dynamic phase transitions in samples of perovskite type manganites of L a 2 3 C a 1 3 Mn O 3 , when they were submitted to the influence of an external magnetic field that includes both a time dependent and a time independent magnetic fields. This study was carried out based on Monte Carlo simulations and using the Metropolis algorithm and the mixed spin Ising model. Exchange parameters are proposed to simulate this material. These exchange parameters were obtained in order to reproduce the critical temperature for L a 2 3 C a 1 3 Mn O 3 . Results showed that it exists a competition between different factors that generate order or disorder in the magnetic behavior of that material. It was observed that, as the time independent field increases, the critical temperature increases. Moreover, simulations showed that as the amplitude or the period of the time dependent magnetic field increases, the critical temperature decreases. This behavior allows to assert that an time dependent magnetic field induced disorder while a time independent field induces order. [ABSTRACT FROM AUTHOR]

In this work, we present a detailed study on the magnetic properties and the magnetocaloric effect (MCE) of La 1−x K x MnO 3 compounds with x =0.05–0.2. Our results pointed out that the Curie temperature ( T C ) could be controlled easily from 213 to 306 K by increasing K-doping concentration ( x ) from 0.05 to 0.2. In the paramagnetic region, the inverse of the susceptibility can be analyzed by using the Curie-Weiss law, χ ( T )= C /( T − θ ). The results have proved an existence of ferromagnetic clusters at temperatures above T C . Based on Banerjee's criteria, we also pointed out that the samples are the second-order phase transition materials. Their magnetic entropy change was calculated by using the Maxwell relation and a phenomenological model. Interestingly, the samples with x =0.1–0.2 exhibit a large MCE in a range of 282–306 K, which are suitable for room-temperature magnetic refrigeration applications. The composites obtained from single phase samples ( x =0.1–0.2) exhibit the high relative cooling power values in a wide temperature range. From the viewpoint of the refrigerant capacity, the composites formed out of La 1−x K x MnO 3 will become more useful for magnetic refrigeration applications around room-temperature. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the magnetic properties and the magnetocaloric effect of La 0.7−x Na x Ca 0.3 MnO 3 compounds, which were prepared by a conventional solid-state reaction technique. The Rietveld refinement results suggested that the samples are single phase belonging to an orthorhombic structure (space group Pnma ). Analyzing temperature dependence of magnetization M ( T ) revealed that the Curie temperature ( T C ) increases with increasing Na content ( x ). Their T C value is found to be 260–298 K for x =0.0–0.1, respectively. Base on M ( T ) data measured at different applied magnetic fields ( H ), temperature dependence of magnetic entropy change Δ S m ( T ) data for all the samples was calculated by using a phenomenological model. In the vicinity of T C, -Δ S m ( T ) curve reaches a maximum value (denoted as |Δ S max |), which gradually increases with increasing H . Under 12 kOe, the value of |Δ S max | is in a range of 1.47–5.19 J/kg K corresponding to the relative cooling power RCP=57.12–75.88 J/kg. Applied the universal master curve method for the magnetic entropy change, we concluded that Na-doped in La 0.7−x Na x Ca 0.3 MnO 3 compounds leads to modification the nature of the magnetic phase transition from the first- to the second-order. [ABSTRACT FROM AUTHOR]

In this work, the magnetocaloric properties of (La 0.45 Nd 0.25 )Sr 0.3 MnO 3 (LNSMO)-based composites are studied. The structural, microstructural, magnetic and magnetocaloric properties of LNSMO and LNSMO/5CuO samples were investigated aiming to particularly clarify the secondary phase (CuO) role in driving the magnetocaloric behavior. The main phase LNSMO crystallizes in a rhombohedral R-3C (1 6 7) configuration. The XRD patterns of composite samples show both perovskite LNSMO and monoclinic Tenorite CuO structures. The microstructural analysis unveils that the CuO phase is mainly present in the grain boundaries and segregates region. On the other hand, it was found that the magnetocaloric effect could be significantly enhanced by adding a small amount of CuO (5% weight ratio). For a magnetic field changing from 0 to 1.5 T, the corresponding isothermal entropy change was found to be 2.55 J/kg K for the LNSMO/5CuO composite while it is only about 1.1 J/kg K for the mother material LNSMO. Our finding should inspire and open new ways for the enhancement of the magnetocaloric effect in manganites-based materials. [ABSTRACT FROM AUTHOR]

The ball milling route has been used to produce the LaSrMnFeO (LSMFO) nanocrystalline sample from oxide precursors. The sample was characterized using x-ray diffraction (XRD), a scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDAX), differential scanning calorimetry (DSC) and thermogravimetric (TGA) measurements. The x-ray diffraction confirms the phase purity of sample and shows that the sample crystallizes in the rhombohedral perovskite structure with a R-3c space group. The scanning electron micrograph shows the presence of well-faceted crystallites of LSMFO. The EDAX spectrum demonstrates the molar ratio of different elements of nanocrystalline LSMFO. Furthermore, the crystallite size using the Debye-Scherrer formula and William-Hall analysis has been found as 24 nm and 29 nm, respectively. Our results support the idea that a good quality nanocrystalline LSMFO sample can be obtained using the ball milling route. We also discuss the DSC and TGA curves and analyse the results in terms of phase transition, calcination temperature and activation barrier energies. [ABSTRACT FROM AUTHOR]

• La 0.8 Na 0.2- x Li x MnO 3 (x = 0 – 0.15) monovalent-doped manganite are synthesized by solid state method. • The influence of A site disorder on electroresistance effect (ER) has been studied. • Resistivity significantly dropped for all samples with the increased in applied current. • Li substitution at x = 0.15 induce Griffith phase (GP) and enhance ER effect at 300 K. • The increased of A site disorder contributes to strong lattice distortion and induce presence of GP. The effects of Li substitution on structural, magnetic properties, and electroresistance (ER) behaviour in La 0.8 Na 0.2- x Li x MnO 3 (x = 0 – 0.15) manganites prepared via the conventional solid-state method were reported. All samples exhibited a metal–insulator transition behaviour with a decrease in the metal–insulator transition temperature, T MI from 270 K (x = 0) to 255 K (x = 0.15) and reduction in Curie temperature, T C from 272 K (x = 0.10) to 235 K (x = 0.15). All samples exhibited a reduction in resistivity under higher applied current of 5 mA than that of 1 mA, which led to an ER effect. Large ER value of −59 % is achieved for sample × = 0.15 at 300 K, thereby indicating its potential application for spintronic-based devices. The competition between the occurrence of lattice distortion and the presence of magnetic inhomogeneity induced by A-site disorder (σ2) is suggested responsible for the observed ER effect. [ABSTRACT FROM AUTHOR]

Hybrid magnetic heterostructures made of epitaxial manganite LaSr MnO thin film and an intermetallic superlattice (TeCo/FeCo) were prepared on orthorhombic NdGaO substrates and characterized by means of magneto-optical Kerr effect, magnetoresistance and ferromagnetic resonance. Experimental data show that magnetic interaction between LaSrMnO and (TeCo/FeCo) is of an antiferromagnetic nature. The features observed in magnetotransport characteristics are caused by the magnetization reversal at the interface between manganite thin film and intermetallic superlattice. [ABSTRACT FROM AUTHOR]

In this study, we have investigated magnetic behavior, magnetocaloric effect and critical exponent analysis of La 0.7-x Eu x Sr 0.3 MnO 3 (x = 0.0, 0.1, 0.2, 0.3) manganites synthesized through solid state reaction route. The crystallographic data obtained from refinement of X-ray diffraction patterns reveal that crystal structure changes from rhombohedral (for x = 0.0) to orthorhombic (for x ≥ 0.1). The average ionic radius of A-site is decreased from 1.384 Å (for x = 0.0) to 1.360 Å (for x = 0.3) with Eu 3+ substitution which in turn decreases the Mn-O-Mn bond angles. Magnetization measurements are performed in the vicinity of T C to determine magnetocaloric effect (MCE) and critical field behavior. The maximum magnetic entropy change ( Δ S M max ) (for μ 0 ΔH = 6 T ) increases with the Eu 3+ substitution from 3.88 J/kg K (for x = 0.0) to 5.03 J/kg K (for x = 0.3) at the transition temperature. The critical field behaviour of compounds was analysed using various methods such as modified Arrott plots, Kouvel-Fisher method and critical isotherm to determine critical temperature and critical exponents ( β , γ and δ ). The obtained critical exponents are in good accordance with scaling relation. The temperature dependence of the order parameter n , for different magnetic fields, is studied using the relation ΔS M αH n . The values of n are found to obey the Curie-Weiss law for temperatures above the transition temperature. The rescaled change in entropy data for all compounds collapses into the same universal curve, revealing a second order phase transition. [ABSTRACT FROM AUTHOR]

The orthorhombic Pr 0.8 Na 0.2−x K x MnO 3 (x = 0.10 and 0.15) manganites are prepared by using the solid state reaction at high temperatures. The critical exponents (β, γ, δ) are investigated through various techniques such as modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis based on the data of the magnetic measurements recorded around the Curie temperature. The critical exponents are derived from the magnetization data using the Kouvel-Fisher method, are found to be β = 0.32(4) and γ = 1.29(2) at T C ~ 123 K for x = 0.10 and β = 0.31(1) and γ = 1.25(2) at T C ~ 133 K for x = 0.15. The critical exponent values obtained for both samples are comparable to the values predicted by the 3D-Ising model, and have also been verified by the scaling equation of state. Such results demonstrate the existence of ferromagnetic short-range order in our materials. The magnetic entropy changes of polycrystalline samples with a second-order phase transition are investigated. A large magnetic entropy change deduced from isothermal magnetization curves, is observed in our samples with a peak centered on their respective Curie temperatures (T C ). The field dependence of the magnetic entropy changes are analyzed, which show power law dependence Δ S max ≈ a ( µ 0 H ) n at transition temperature. The values of n obey to the Curie Weiss law above the transition temperature. It is shown that for the investigated materials, the magnetic entropy change follow a master curve behaviour. The rescaled magnetic entropy change curves for different applied fields collapse onto a single curve for both samples. [ABSTRACT FROM AUTHOR]

Based on the modified Arrott plots and the critical isotherm analysis, the critical exponents of both LaCaMnO and LaCaAgMnO systems have been comprehensively studied and investigated near the paramagnetic-ferromagnetic (PM-FM) phase transition. Critical exponents, β, γ, and δ, which are corresponding to the thermal variation of the spontaneous magnetization, initial susceptibility, and the isothermal magnetization, respectively, obeyed the Widom scaling law δ = 1 + γ/β. It indicates thus the validity the obtained results. We performed then another analysis of the critical behavior via the magnetocaloric effect presenting an accord with the analysis of magnetization measurements. Relative cooling power (RCP) follows the evolution of the magnetic field as RCP ∼ H . The acquired critical exponents were in conformity with those gotten from the modified Arrott plots and Widom scaling law. [ABSTRACT FROM AUTHOR]

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