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Abstract In this study, we have investigated the crystallographic structure and the temperature-dependent resistivity of an electron doped La 1-x Zr x MnO 3 manganite system. X-ray photoemission spectroscopy (XPS) for core level study has been carried out to confirm the electron doping. The results of XPS core level study suggests that Zr ions are in the tetra-valent state and Mn ions are forced to be in a mixed state of Mn3+ and Mn2+. Rietveld refinement of X-ray powder diffraction results have confirmed the rhombohedral crystal symmetry of the samples with space group R-3c. The temperature dependent resistivity and magnetization plots exhibit insulator to metal transition (MIT) accompanied with Paramagnetic to Ferromagnetic transition (T c). Three independent MIT transitions have been observed, the first sharp transition at T P1 showed a strong correlation with the magnetic transition T c confirming that the intrinsic MIT happened at T P1. The insulating behaviour below T 1 has been attributed to the competition between the short range orbital/charge order and the long range FM order. The transition at lower temperature T P2 may be attributed to the percolative transport of charge carriers through ferromagnetic metallic domains. The third upturn transition assigned as T min has been ascribed to combined effect of electron-electron and Kondo interactions, the detailed qualitative analysis and discussion of which is under preparation. Highlights • Electron doped manganite system La 1-x Zr x MnO 3 were synthesized using solid state reaction method. • The system has a rhombohedral crystal symmetry with space group R-3c. • XPS core level study suggests electron doping of the system. • The system exhibits metal to insulator (MIT) transition accompanied by the Ferromagnetic (FM) to Paramagnetic (PM) transition. • Three independent MIT transitions have been observed, attributed to different physical phenomenon. [ABSTRACT FROM AUTHOR]

We report the effect of MgO phase on structural, electric and thermo electric properties of La 0.8 Sr 0.2 MnO 3 (LSMO) and manganite matrix-based composite series (1− x ) La 0.7 Ca 0.2 Sr 0.1 MnO 3 + ( x ) MgO with x = 0.0, 0.05, 0.10, 0.15 (abbreviated as LCSMO - MgO) synthesized by solid-state reaction method. X-ray diffraction (XRD) data infers that manganite LSMO compound possesses a rhombohedrally-distorted structure (space group R 3 c ), LCSMO has an orthorhombic structure ( Pnma space group) while to that MgO compound crystallizes in cubic structure (space group Fd3m ). XRD shows coexistence of MgO and La 0.7 Ca 0.2 Sr 0.1 MnO 3 phases in doped composites through their characteristic peaks. The temperature dependence of resistivity shows that the transport behavior of the composites is governed by the grain boundaries. These composites shows metal–insulator transitions at T = T MI which decreases with increasing MgO concentration. The magnetoresistance (MR) in this system increases with increasing MgO content, showing a maximum value (91% at 50 K and at lower fields) for (0.85) LCSMO - (0.15) MgO sample, which is larger than the largest MR value of pure La 0.7 Ca 0.2 Sr 0.1 MnO 3 (44% at 50 K). From thermoelectric power measurements, it is observed that electron-magnon scattering process is dominant mechanism in the low temperature region. [ABSTRACT FROM AUTHOR]

We have synthesized a series of Sm 0.55 Sr 0.45−x Ag x MnO 3 (x = 0 & 0.15) by conventional solid state reaction method to scrutinize the effect of monovalent Ag + as a replacement of Sr 2+ ion on structural, electrical, magnetotransport and thermoelectric properties. The structural parameters obtained using Rietveld refinement of X-ray diffraction data which showed perovskite structure having orthorhombic ( Pnma ) symmetry without any detectable impurity phase. It is observed that M ZFC and M FC curves become more manifested as Ag + content is increased which indicates an increase in magnetic frustration arising due to bending of Mn-O-Mn bond. The M-H plots show the narrow hysteresis loops which indicate the soft ferromagnetic nature. Magnetic studies also show that the Curie temperature T C is found to decrease with Ag + content. The metal–insulator transition temperature (T MI ) is observed which decreases with the increase of Ag + content when magnetic field is applied. The resistivity data in high temperature region are explained within the framework of variable range hopping (VRH) and small polaron hopping (SPH) models. The thermoelectric power (S) of the reported samples exhibits a crossover from positive to negative value and value of S increases in doped samples. The analysis of thermoelectric power data confirms that the small polaron hopping model in high temperature region and at low temperature electron–magnon scattering is the dominating in the FM region. With increasing the Ag + content the samples showed very high magneto-resistance (MR%) and temperature coefficient of resistance (TCR%) which make the compound more promising for scientific and technological applications. [ABSTRACT FROM AUTHOR]

A number of experiments have been performed to study magnetic, electronic and optical properties of HoNiSi, along with theoretical calculations. The compound crystallizes in orthorhombic crystal structure and orders antiferromagnetically at T N = 4.6 K. Magnetization isotherms show curvature in low fields, revealing a field induced metamagnetic transition. Application of field reduces the resistivity near T N , which results in a large negative MR. The maximum value of MR has been found to be −24% at 4 K for 50 kOe. Strong antiferromagnetic interactions among the moments below 4 K result in positive MR, which changes with field. The antiferromagnetic ordering with the effective magnetic moments of Ho close to the observed value is obtained in the LSDA + U calculations accounting for the electronic correlations in the 4f Ho shell. In the experimental optical conductivity interband transitions involving 4f Ho and 5d Ho forms the main features in good agreement with the theoretical electronic structure of HoNiSi. [ABSTRACT FROM AUTHOR]

A systematic study on the structural, electrical, magnetic and thermo-electric properties of La 0.8 Ba x Ca 0.2 − x MnO 3 (0 ⩽ x ⩽ 0.2) manganites is carried out in the present work. The samples have been prepared using solid state reaction technique. All the samples are single phased. It is seen that Ba-doping introduces a structural phase transformation viz. from rhombohedral to cubic system. Electric and magnetic studies respectively show that the metal–insulator transition temperature, T MI and Curie temperature, T C increase with Ba-content. Magneto-resistance (MR) data shows that it decreases with Ba-doping. Analyses of the electrical transport data in metallic region i.e. T < T MI shows that the electrical transport is governed predominantly by electron–electron scattering process. On the other hand, the adiabatic small polaron hopping (ASPH) model is appropriate in the high-temperature insulating range viz. T > T MI . We have used the electrical resistivity data in the entire temperature range (50–300 K) and analyzed using the phenomenological percolation model which is based on the phase segregation mechanism. We have analyzed the Seebeck coefficient data which reveals that the small polaron hopping mechanism is operative in high temperature regime and the low temperature region is examined by taking into account the impurity, electron–magnon scattering, and spin wave fluctuation terms. It is established that the electron–magnon scattering is dominating for the thermoelectric transport below T MI . [ABSTRACT FROM AUTHOR]

Influence of BTO phase on structural and electric properties of LSMO phase has been investigated by synthesizing a manganite matrix-based composite series (1 − x )La 0.67 Sr 0.33 MnO 3 + ( x )BaTiO 3 with x = 0.0, 0.05, 0.10, 0.15, 0.20, and 0.25 (abbreviated as LSMO–BTO) by solid-state reaction method. Rietveld refined X-ray diffraction (XRD) data infers that manganite LSMO compound possess a rhombohedrally-distorted structure (space group R 3 c ), while to that BTO compound crystallizes in tetragonal structure (space group P 4 mm ). The structural parameters and the reliability factors for the LSMO–BTO composite ceramics were successfully determined by the Rietveld refinement. The resistivity measurements infer that the metal–insulator transition temperature was shifted towards lower temperature as well as resistivity increases with increasing BTO content in LSMO–BTO composites. Measurement of resistivity of these samples shows more prominent extrinsic metal insulator (EMI) transition at temperature T EMI . At H = 8 T, the magnetoresistance is enhanced in the wide temperature ranges due to introduction of BaTiO 3 content in La 0.67 Sr 0.33 MnO 3 which could be explained by enhanced spin polarized tunneling. [ABSTRACT FROM AUTHOR]

Abstract: A systematic study of the magneto-resistance (MR), magneto-reactance (MX), and magneto-impedance (MI) effects in single and multiple glass-coated amorphous Co68B15Si10Mn7 microwires is reported. Our studies reveal that the MR, MX, and MI ratios and their corresponding magnetic field sensitivities strongly depend on the number of microwires in an array and on the distance between them. We find that increasing the number of microwires increases the MR and MI ratios and their field sensitivities (ηR and ηZ , respectively) but decreases the MX ratio and its field sensitivity (ηX ). A similar trend is observed for the frequency dependence of these parameters. Increasing the distance between the wires is also found to decrease the MR and MI ratios but increase the MX ratio of the array considerably. From a sensor application perspective, it is interesting to note that for the case of a single microwire, the ηX reaches a value as high as 960%/Oe at a frequency of 1MHz, which is about 192 times of the ηR or ηZ (∼5%/Oe), revealing the possibility of developing ultrahigh sensitivity magnetic field sensors based on the principle of the MX effect. [Copyright &y& Elsevier]

• A single crystal of SnSb 2 Te 4 is grown by using a simple self-flux method. • Crystalline growth and phase purity are evident from XRD, SEM, and EDAX measurements. • Two different Raman modes are observed in parent Sb 2 Te 3 due to changes in the middle atomic layer. • We are the first to report MR% behavior of SnSb 2 Te 4 +5T. • Presence of WAL effect in SnSb 2 Te 4. • DFT calculated bulk electroic band structure of SnSb 2 Te 4. Here, we report successful single crystal growth of SnSb 2 Te 4 using the self-flux method. Unidirectional crystal growth is confirmed through X-ray Diffraction (XRD) pattern taken on mechanically cleaved crystal flake while the rietveld refined Powder XRD (PXRD) pattern confirms the phase purity of the grown crystal. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) image and Energy Dispersive X-Ray analysis (EDAX) confirm crystalline morphology and exact stoichiometry of constituent elements. Vibrational Modes observed in Raman spectra also confirm the formation of the SnSb 2 Te 4 phase. DC resistivity (ρ-T) measurements confirm the metallic character of the grown crystal. Magneto-transport measurements up to±5T show a non-saturating low magneto-resistance percentage (MR%). V-type cusp and Hikami Larkin Nagaoka (HLN) fitting at lower field confirms the Weak Anti-localization (WAL) effect in SnSb 2 Te 4. Density Functional Theory (DFT) calculations were showing topological non-trivial electronic band structure. It is the first-ever report on MR study and WAL analysis of SnSb 2 Te 4 single crystal. [ABSTRACT FROM AUTHOR]