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This work deals with the synthesis of hole-doped La1-xSrxMnO3 (x = 0.25 and 0.33) perovskite via two different ways, namely a solid-state reaction method and a sol-gel process. Various properties of the samples have been investigated and compared by means of different techniques, namely X-ray diffraction (XRD), temperature-dependent resistivity measurements in the temperature range 25-300 K using a closed cycle refrigerator and vibrating sample magnetometry (VSM). All samples have orthorhombic crystal symmetry and an irregular variation in unit-cell volume with increase in Sr content. The average crystallite size was determined from the XRD data and found to lie in the range 19-22 nm. Metal-insulator transitions (MIT) were observed in all the samples via low-temperature electrical characterisations. The magnetic measurements confirm that the magnetisation does not saturate for the 25% Sr doped samples up to the available field of 10 kOe. The magnetic response also supports the interpretation of XRD and resistivity data. The obtained results are explained on the basis of double-exchange and super-exchange mechanisms. [ABSTRACT FROM AUTHOR]

We present experimental and theoretical studies on the effect of Fe doping at Mn site, on the structural, morphological, electronic and vibrational properties of La 0.67 Sr 0.3 MnO 3 nanoparticle. The samples of La 0.67 Sr 0.3 MnO 3 and La 0.67 Sr 0.33 Mn 1-x Fe x O 3 (x = 0.15, 0.25 and 0.35) have been prepared by ball milling route. The phase purity of these samples has been confirmed using X-ray diffraction, while compositional analysis is done using EDAX. The morphological analysis done using scanning microscope indicates the agglomeration. The vibrational analysis which is done using Raman scattering and density functional theory (DFT) calculations show a substantial shift in A 1g and E g modes with Fe doping. The E g modes become broader with Fe doping. The UV–visible spectra were measured in the energy range of 1–5 eV and compared with DFT results. The spin polarized density functional calculations show an increase in density of states at Fermi level due to MnO 6 octahedra modification and significant magnetism on Fe doping. The total magnetic moment is found from 16 to 17 μ B for considered concentration. The effective mass of carriers is also calculated and found increasing with increasing concentration. [ABSTRACT FROM AUTHOR]

Single phasic La 0.67 Ca 0.33 Mn 1–x Sb x O 3 (LCMSO; x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) samples were characterized by performing temperature and magnetic field dependent resistance measurements. Present study, mainly, aims for the better understanding of possible charge conduction mechanisms responsible for the low temperature resistivity and high temperature [well above metal to insulator transition temperature (T P )] semiconducting regions. Variation in resistivity and T P with Sb 5+ content (x) and applied magnetic field has been discussed in the light of the modifications in structural and magnetic lattices of smaller diamagnetic Sb 5+ doped LCMSO system. Various models and mechanisms have been theoretical employed to fit obtained experimental resistivity data for the low temperature resistivity and semiconducting regions of all LCMSO manganites. It is found that low temperature resistivity minima follows the coulomb blockade model while charge conduction in the semiconducting region obeys the variable range hopping (VRH) mechanism. Variation in low temperature blocking energy, activation energy in semiconducting region and magnetoresistance (MR) with Sb 5+ content (x) and applied magnetic field has been discussed in detail. [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]

We report the thermoelectric (TE) properties of (1-x)LaCoO 3 .xLa 0.7 Sr 0.3 MnO 3 (0 < x < 0.50) composite in a temperature range 320–800  K . Addition of La 0.7 Sr 0.3 MnO 3 to LaCoO 3 in small amount (5 weight %) improves the overall Seebeck coefficient ( α ) at higher temperatures. The electrical conductivity however decreases due to a decrease in carrier concentration of the composite. The decrease in electrical conductivity of the composite at high temperature may be attributed to the insulating nature of the LSMO above room temperature. Thermal conductivity ( κ ) of all the samples increases with an increase in the temperature, but decreases with increasing LSMO content. We also report the local variation of Seebeck coefficient across the composite samples measured using a precision Seebeck measurement system. A maximum value of 0.09 for the figure of merit ( ZT ) is obtained for 0.95LaCoO 3 .0.05La 0.7 Sr 0.3 MnO 3 at 620 K which is significantly higher than the ZT of either of LaCoO 3 or La 0.7 Sr 0.3 MnO 3 at 620 K. This suggests the potential for enhancement of operating temperatures of hitherto well known low temperature thermoelectric materials through suitable compositing approach. [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]

Structural, electrical and magnetic properties of Dy 1-x Ba x MnO 3 compounds synthesized by the standard solid state reaction route are reported in this paper. For x = 0.0 to 0.5, the compounds have orthorhombic structure and for x = 0.8 and 1.0, the structure changed to hexagonal structure corresponding to 2H. Raman spectra of the materials compliment structural phase transition. Phonon lifetimes estimated from the Raman line width were found to be in the order of pico seconds. X-ray photoelectron spectra of Dy 1-x Ba x MnO 3, revealed the presence of Dy, Ba, Mn and O elements with respective binding energies. Mn ions were found to be in the mixed valent states of Mn (III) and Mn (IV) and their ratio decreased with increasing Ba concentration. Temperature behavior of electrical resistivity of all the compounds showed semiconducting behavior that persisted in the entire temperature range with small polaron hopping conduction mechanism. As Ba content increased, activation energies for hopping of polarons decreased in the orthorhombic phase and increased in the hexagonal phase. Magnetic studies as a function of temperature indicated that ordering temperatures of rare earth (Dy) moments are suppressed with Ba substitution. Random occupation of magnetic Dy 3+ , Mn 3+ and Mn 4+ ions in Dy 1-x Ba x MnO 3 system resulted in complex magnetic structures. The reduction in the experimental effective magnetic moments determined from the Curie-Weiss fit parameters followed the magnetic dilution. Isothermal magnetization curves confirmed the presence of multiple interactions between the magnetic ions. [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]

In this study, we have investigated the structural, magnetic and thermoelectric properties of La 0.4 Bi 0.4 Ca 0.2 Mn 1− x Co x O 3 (0 ≤  x  ≤ 0.3) manganites. The crystallographic parameters of samples were determined by the Rietveld refinement of powder X-ray diffraction data. It was observed that Co doping results in change of crystal structures from orthorhombic (space group: Pbnm ) to rhombohedral (space group: R-3c ) symmetry. Scanning electron microscopy (SEM) images show smooth, clean and densified structures, depicting good crystallinity of samples. The zero field cooled (ZFC) and field cooled (FC) magnetization data were collected in the temperature range 5 to 300 K under an applied magnetic field of 0.1 Tesla. The analysis of temperature dependent magnetization data reveals all samples to be ferromagnetic with Curie temperatures around ∼77 K. The magnetic hysteresis loops, collected at 5 K, show that the saturation magnetization ( M S ) values decrease from 43 emu/g to 14 emu/g with increase in Co doping. The high temperature thermoelectric properties of all samples are characteristic of a semiconducting behavior, the small polaron hopping model fitting well with the temperature dependent electrical resistivity ( ρ ) and thermopower ( S ) data. The thermopower values change sign from positive to negative as temperature is increased from 313 K to 680 K. The maximum thermoelectric power factor (PF =  S 2 / ρ ) obtained for x  = 0.3 sample at 313 K is 4.60 μW/mK 2 , is much higher than for the undoped sample. [ABSTRACT FROM AUTHOR]

The effect of Ni 2+ doping on the magnetic and magnetocaloric properties of La 0.7 Ca 0.3 MnO 3 manganites synthesized via the auto-combustion method is reported. The aim of studying Ni 2+ -substituted La 0.7 Ca 0.3 Mn 1 − x Ni x O 3 ( x = 0 , 0.02 , 0.07 , and 0.1) manganites was to explore the possibility of increasing the operating temperature range for the magnetocaloric effect through tuning of the magnetic transition temperature. X-ray diffraction analysis confirmed the phase purity of the synthesized samples. The substitution of Mn 3+ ions by Ni 2+ ions in the La 0.7 Ca 0.3 MnO 3 lattice was also corroborated through this technique. The dependence of the magnetization on the temperature reveals that all the compositions exhibit a well-defined ferromagnetic to paramagnetic transition near the Curie temperature. A systematic decrease in the values of the Curie temperature is clearly observed upon Ni 2+ doping. Probably the replacement of Mn 3+ by Ni 2+ ions in the La 0.7 Ca 0.3 MnO 3 lattice weakens the Mn 3+ –O–Mn 4+ double exchange interaction, which leads to a decrease in the transition temperature and the magnetic moment in the samples. By using Arrott plots, it was found that the phase transition from ferromagnetic to paramagnetic is second order. The maximum magnetic entropy changes observed for the x = 0 , 0.02 , 0.07 , and 0.1 composites was 0.85, 0.77, 0.63, and 0.59 J/kg K, respectively, under a magnetic field of 1.5 T. In general, it was verified that the magnetic entropy change achieved for La 0.7 Ca 0.3 Mn 1 − x Ni x O 3 manganites synthesized via the auto-combustion method is higher than those reported for other manganites with comparable Ni 2+ -doping levels synthesized via standard solid state reaction. The addition of Ni 2+ increases the value of the relative cooling power as compared to that of the parent compound. The highest value of this parameter (∼60 J/kg) is found for a Ni-doping level of 2% around 230 K in a field of 1.5 T. [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]

Nd x AE 2-x MnO 4±δ (AE: Ca, Sr) manganites with x = 0.25, 0.4, 0.5 and 0.60 are part of the Ruddlesden-Popper family of generic formula A n+1 B n O 3n+1 with n = 1. The compositions range that can be successfully synthesized by the sol-gel method in air has been identified. While Sr compounds are stable in reducing atmosphere (3% H 2 /Ar - 850 °C/16 h), Ca ones decompose when submitted to such atmosphere. Nd 0.5 Sr 1.5 MnO 4±δ was analyzed by High-Temperature X-ray diffraction (HT-XRD) showing TEC values of 12.7 × 10 −6  K −1 and 14.4 × 10 −6  K −1 in air and 3% H 2 /N 2 (25–800 °C), respectively. Using standard conditions for electrode elaboration, the material reacts with YSZ electrolyte, but is chemically compatible with GDC electrolyte. A small polaron-type behavior is observed for the electrical conductivity of Nd 0.5 Sr 1.5 MnO 4±δ in air and 3% H 2 /Ar , with respective values of 33.4 S cm −1 and 0.9 S cm −1 at 800 °C, meeting the preliminary requirements for use as symmetrical SOFC electrode. [ABSTRACT FROM AUTHOR]

In the present communication, we present results on the effect of rare-earth (RE) substitution at La-site on the structural, electrical and thermoelectric properties of La 0.7−x RE x Sr 0.3 MnO 3 compounds. The lattice parameters are observed to decrease with RE-doping which is attributed to the fact that the substituted RE ions (RE = Eu, Gd and Y) are smaller than that of La ion. In high temperature semiconducting regime, small polaron hopping (SPH) model is valid, whereas, variable hopping model is valid in low temperature metallic region. The resistivity in the entire temperature range follows percolation model. All the samples exhibit sign reversal in thermopower, S . From temperature dependent S data, it is seen that SPH model is applicable in high temperature regime. [ABSTRACT FROM AUTHOR]

Orthorhombic GdMnO3 is studied using density functional theory considering the pseudo-potential plane-wave method within local-spin-density approximation, LSDA. The electronic band structure and density of states, for several hydrostatic pressures, are studied. The Mott transition was observed at 60 GPa. Calculated lattice parameters are close to the experimental measurements, and some indirect band gaps (S→Γ) were obtained within the LSDA level of calculation, between the occupied O-2p and unoccupied Gd-4f states. The variation of the gap reduces with increasing pressure, being well fitted to a quadratic function. [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]

Experimental data on structural, magnetic, and electrical features of manganites of the system La0.65Sr0.35-cCecMn1 - xZnxO3 + γ (c = 0, 0.05; x = 0, 0.05, 0.10), synthesized by ceramic processing, are reported. Part of the samples were annealed under conditions that yield stoichiometric oxygen content. The samples obtained are of rhombohedral structure, but contain the impurity of the CeO2 phase. The introduction of cerium and zinc leads to a decrease in the unit cell volume of the rhombohedral phase. Cerium does not substantially affect the magnetization and Curie point of the initial samples. The width of the “ferromagnetic-paramagnetic” transition temperature interval rises after annealing, especially in manganite with high zinc content. Initial and annealed samples of composition with c = 0.05, x = 0.10 exhibit the phase transition “metal-semiconductor” at temperatures of about 219 K and 200 K, respectively. All other manganites possess a metallic character of conductivity in the range of 100-300 K. The maximum absolute value of magnetoresistance reaches 52%. The approaches to the interpretation of experimental results are discussed. [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]

“Ab-initio” calculations of the electronic structure of the heterojunction (001) between cubic CaMnO3 and BaTiO3 perovskites are performed on the basis of density functional theory for different variants of magnetic ordering in calcium manganite. The paper considers some cases of ferromagnetic and antiferromagnetic A-type ordering. Comparison of the total energies of these structures shows that antiferromagnetic ordering in CaMnO3 is the most favorable. All the studied structures in a ferromagnetic state are half-metallic ferromagnets. [ABSTRACT FROM AUTHOR]

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• 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]

We investigated the influence of 10% substitution of rare-earth (RE) elements on the crystallographic, transport, and magnetic properties of La _0.67– _x RE _x Ca _0.33 MnO _3 (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, T _c , 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.