Structural Characterization and Physical Properties of Double Perovskite La2FeReO6+δ Powders

The structural, optical, dielectric, and magnetic properties of double perovskite La2FeReO6+δ (LFRO) powders synthesized by solid-state reaction method under CO reduced atmosphere are reported on in this paper. Reitveld refinements on the XRD data revealed that the LFRO powders crystallized in an orthogonal structure (Pbnm space group) with column-like morphology. The molar ratios of La, Fe, and Re elements were close to 2:1:1. XPS spectra verified the mixed chemical states of Fe and Re ions, and two oxygen species in the LFRO powders. The LFRO ceramics exhibited a relaxor-like dielectric behavior, and the associated activation energy was 0.05 eV. Possible origins of the dielectric relaxation behavior are discussed based on the hopping of electrons among the hetero-valence ions at B-site, oxygen ion hopping through the vacant oxygen sites, and the jumping of electrons trapped in the shallower level created by oxygen vacancy. The LFRO powders display room temperature ferromagnetism with Curie temperature of 746 K. A Griffiths-like phase was observed in the LFRO powders with a Griffiths temperature of 758 K. The direct optical band gap of the LFRO powders was 2.30 eV, deduced from their absorption spectra, as confirmed by their green photoluminescence spectra with a strong peak around 556 nm.

Colossal magnetoresistance of Nd-doped LaCaMnO3 polycrystalline ceramics

The cation doped polycrystalline compound La0.5Nd0.15Ca0.35MnO3 has been synthesized by a conventional solid state reaction method. The Rietveld analysis of the powder XRD of the composites reveals an orthorhombic structure with Pbnm space group symmetry. The cell parameters are a = 5.4505 ?, b = 5.4457 ? and c = 7.6876?. The AC magnetization studies show a semiconducting paramagnetic to metallic ferromagnetic transition at a temperature below the Curie temperature TC which is found to be 206.3K. It is also observed that metal to semiconductor transition temperature TMS is very close to TC. The sample also possesses high magnetoresistance, which is revealed in MR studies.

Effect of Bi Substitution on Structural and AC Magnetic Susceptibility Properties of Nd1−xBixMnO3

This study synthesizes the neodymium-based manganites with Bi doping, Nd1−xBixMnO3 (x = 0, 0.25 and 0.50) using the solid-state reaction route. The crystal structural, morphological and magnetic properties were determined using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and AC magnetic susceptibility. The Rietveld refinement confirmed that the compounds were in the single-phase orthorhombic structure of the NdMnO3 with Pbnm space group and lattice parameter b increased with doping from 5.5571 (x = 0) to 5.6787 (x = 0.5). FTIR spectra showed that absorption bands were located within the range of 550–600 cm−1, which corresponded to the Mn–O stretching vibration. FESEM exhibited homogenous compound. The AC magnetic susceptibility measurement studies showed a strong antiferromagnetic (AFM) to paramagnetic (PM) transition existed at 76 K, 77 K and 67 K for samples (x = 0, 0.25 and 0.50), respectively.

Effect of Zr addition on structure and electrical properties of SmFeO3 prepared by solid state reaction method

Series of Sm1-xFe1-3xZr3xO3 (SFZO, where x = 0.0, 0.01, 0.02, 0.033, 0.05, 0.1 and 0.15), was synthesised by the solid state reaction method and sintered at 1500?C in air. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the structure of the materials. The XRD results indicated that the pure SmFeO3 and Sm0.99Fe0.97Zr0.03O3 samples are single phase materials with an orthorhombic symmetry and Pbnm space group. The increase of Zr content (x ? 0.02) causes a phase change from single to twophase system with orthorhombic (Pbnm) and fluorite symmetry (Fm?3m). The microstructural analyses showed that the Zr4+ doping resulted in an increase of porosity in the sintered SFZO compared to SmFeO3 sample. The direct current (DC) electrical conductivity at 850?C in air was found to be 0.045 S/cm and 0.007 S/cm for Sm0.99Fe0.97Zr0.03O3 and SmFeO3, respectively, showing a significant enhancement compared to the pure SmFeO3.

Magnetization Reversal in PrCrO3

PrCrO3(PCO) samples were prepared by Citric acid route .The samples were characterized by XRD and SEM. The sample exhibits a single phase orthorhombic structure with Pbnm space group. The temperature dependent and field dependent magnetic measurements were measured in the range of 5K-400K at 100 Oe field and 0 to 5T field at 5K and RT respectively .The temperature dependence of dc magnetic properties show that the ZFC and FC magnetization curves are irreversible strongly and nearly symmetrical below 240K .There appears a novel magnetization behavior with negative magnetization characteristic in ZFC, the diamagnetism like behavior .This behavior exhibits the coexistence of canted anti-ferromagnetic and weak ferromagnetic phase and the existence of competition mechanism below 240K . This behavior can be interpreted from the interaction between Pr3+and Cr3+moments .The field and temperature dependent magnetization indicates the phase transition from canted anti ferromagnetic to paramagnetic occurred below 240K. In the region of higher temperature above 240K, PrCrO3behaved as a typical Curie-Weiss paramagnetic.Keywords: Orthochromites ,Multiferroics ,Neel temperature.PACS: 75.85 +t, 75.60 d, 75.50.Ee,75.30 Et,76.30 Kg

Effects of Film Thickness on Laser Induced Voltage (LIV) of La2/3Ca1/3MnO3:Ag0.05 Thin Films Grown on LaAlO3 Substrates

La2/3Ca1/3MnO3:Ag0.05(LCMO:Ag0.05) thin films were prepared on vicinal cut LaAlO3(LAO) substrates with various film thicknesses by pulsed laser deposition technique (PLD). XRD results show that all the samples are shown along the (00l) orientation in orthorhombic structure with Pbnm space group. While the film thickness is around 450nm, the optimum LIV effects of the epilayer thin film have been obtained. The LIV effects enhancement of the LCMO:Ag0.05 thin films due to the photon scattering effects have been restrained and anisotropic seebeck coefficient improved.

Synchrotron X-Ray Powder Diffraction Studies of Structural Phase Transitions in Perovskite Oxides

The utilization of the high resolution powder diffractometer at the Australian Synchrotron to obtain accurate and precise structures of some perovskite-type oxides is described. The structure of CdTiO3 has been studied from room temperature to 1000°C by high-resolution synchrotron X-ray powder diffraction. It was found that CdTiO3 remains orthorhombic in the Pbnm space group over the entire temperature range, with the expansion in the cell volume well fitted to the expression . The magnitudes of the TiO6 tilts are estimated from the refined structural parameters and these progressively reduce as the temperature is increased. The effect of Sr content on the room temperature structure of the double perovskites Ba2–xSrxInTaO6 is also described. At room temperature Ba2InTaO6 crystallizes in a cubic structure in space group . Doping with Sr results in tilting of the corner sharing octahedra with a concurrent lowering of symmetry with the sequence of structures being

Behavior of Clustered State above the Curie Temperature in La0.78Ca0.22MnO3 Single Crystal

The results of structural neutron diffraction study and the data on the transport and magnetic properties (the linear and nonlinear (second and third order) susceptibilities) are presented for the La0.88Ca0.22MnO3 single crystal. This compound has the orthorhombic Pbnm space group, showing no structural transformations between 90 K and 300 K. It exhibits the paramagnet-ferromagnet (P-F) (TC  186 K) and insulator – metal (I-M) (ТIM  201 K > TC) phase transitions. The measurements of the second harmonic of the magnetization in the parallel ac and dc H magnetic fields, M2(H,T), showed that below T* 252 K, the FM clusters appear in the PI matrix undergoing the second-order transition. The concentration of the FM clusters increases with cooling so that it is above the percolative threshold value below TIM, and the sample exhibits metallic behavior. The M2(H) hysteresis loops possess a high sensitivity to the I-M transition. Their usual central symmetry is broken in the vicinity of TIM and the loops become asymmetric. This effect is attributed to cluster link nucleation-and-growth process.

PRESSURE-RELATED PHASE STABILITY OF MgSiO3and(Mg0.75, Fe0.25)SiO3 AT LOWER MANTLE CONDITION

Relative stability of different phases for MgSiO 3 and ( Mg 0.75, Fe 0.25) SiO 3 within 0–110 GPa are investigated using first-principles method. For MgSiO 3, the computed equation of state for orthorhombic phase of Pbnm space group agrees well with experimental results. The relative stability reduces from observed Pbnm orthorhombic phase to intermediated tetragonal P4mbm phase, and then to hypothetical cubic [Formula: see text] phase. For ( Mg 0.75, Fe 0.25) SiO 3, the same sequence of relative phase stability is observed. Thus, the low-symmetric orthorhombic MgSiO 3 should be favored in the lower mantle condition, while adding Fe into MgSiO 3 will make it less stable at the same depth.

Preparation of Red Long Afterglow Phosphorescent Material CaTiO3: Pr3+

CaTiO3:Pr3+ was prepared by high temperature solid state reaction and measured by SEM, XRD, excitation and emission spectra. The samples obtained possessed orthorhombic crystal structure of CaTiO3, belonging to Pbnm space group. Excitation spectra of the samples were broad band, their peaks and shoulder peaks were located at about 335nm, 379nm respectively. Emission spectra were single narrow band, emission peaks were located at about 602nm, corresponding to emission of 1D2→3H4 of Pr3+ion. The addition of Eu3+and Dy3+ as co-activator led phosphorescent intensity to greatly enhance, the addition of AgNO3 as ion compensator made the samples material pink and vibrant.