Masroor Ahmad Bhat

Structural, electrical and magnetic features of Kagomé YBaCo4O7 system

Abstract Polycrystalline yttrium barium cobaltite (YBaCo4O7) powdered sample was prepared by conventional solid state reaction route using high purity yttrium oxide, barium carbonate and cobalt oxide. The as-prepared sample was characterized by XRD diffraction, SEM/EDAX, Raman analytical techniques, resistivity and magnetization measurements for structural, morphological, electrical and magnetic properties assessment. XRD pattern confirms the single phase formation of the sample without any impurity. SEM image shows the hexagonal growth of the crystal and EDAX spectrum reveals stoichiometric composition of as prepared sample. The variation in electrical resistivity from 90 K to 300 K follows the variable range hopping conductivity mechanism. The strong broad overlapped Raman peaks of Co–O and Y–O stretching and bending vibrations of tetrahedral CoO4 with included components of YO6 of octahedral symmetry are obtained at 542 cm−1, 486 cm−1 and 636 cm−1, 436 cm−1, respectively. DC magnetic susceptibility exhibits very weak ferromagnetism below 80 K and does not obey Curie-Weiss law.

Magnetic and transport properties driven by Sr substitution in polycrystalline Pr1-xSrxCoO3 (0.1 ≤ x ≤ 0.5) cobaltites

The effect of strontium (Sr) doping on the structural, magnetic, electrical, and thermal properties of Pr1-xSrxCoO3 (0.1 ≤ x ≤ 0.5) has been studied. The samples were synthesized by using the conventional solid-state reaction method. The Rietveld refinement of X-ray diffraction patterns confirms the single-phase composition with orthorhombic (Pbnm) perovskite symmetry. The magnetization measurements revealed the paramagnetic to ferromagnetic transition and the transition temperature (Tc) increased with increasing Sr doping. The effective magnetic moments determined by the Curie-Weiss law show an increase in the Sr concentration. The temperature dependence of electrical resistivity suppressed with increasing the Sr content. Moreover, all the compounds other than x = 0.5 show the semiconducting nature. All semiconductor compositions (x = 0.1, 0.2, 0.3, and 0.4) in the high temperature region can be explained within the framework of the small polaron hopping model and the variable range hopping model, wherea...

Conduction mechanism in Eu0.5Sr0.5Mn0.9Cr0.1O3 perovskite

A systematic study of polycrystalline sample with composition Eu0.5Sr0.5Mn0.9Cr0.1O3 has been undertaken and synthesized by conventional solid state reaction techniques. The room temperature XRD study reveals the single phase formation of the reported compound with orthorhombic structure having Pbnm space group. The temperature dependent resistivity study indicates the highly resistive nature of the compound especially in the low temperature region exhibits a semiconductor behavior and favored the variable range hopping conduction model. The obtained experimental data in the temperature range of our study can be described by the equation ρ(T) = ρ0exp[(T*/T)1/4]. The fitting results are used for the calculation of the temperature scale T* ∼ 9.05×106 K and finally the density of state at Fermi level N(EF) is calculated to be ∼ 61.63 × 1018 eV−1 cm−3.

Transport properties of (Ca1−xSrx)Mn0.95Sb0.05O3 perovskites

The transport properties as a function of composition and temperature of (Ca{sub 1−x}Srx)Mn{sub 0.95}Sb0.{sub 05}O{sub 3} perovskite compounds have been investigated for the first time using extended rigid ion model (ERIM). (Ca{sub 1−x}Srx)Mn{sub 0.95}Sb0.{sub 05}O{sub 3} (x = 0.0, 0.10, 0.15 and 0.17) exhibit a single phase with an orthorhombic perovskite structure (Pnma). Furthermore, to understand better the thermodynamical properties of the present system, ERIM is developed and applied to study the specific heat for these compounds over a wide range of temperature. The trends of variation of computed thermodynamical and transport properties have shown remarkable good agreement with corresponding experimental data.The transport properties as a function of composition and temperature of (Ca1−xSrx)Mn0.95Sb0.05O3 perovskite compounds have been investigated for the first time using extended rigid ion model (ERIM). (Ca1−xSrx)Mn0.95Sb0.05O3 (x = 0.0, 0.10, 0.15 and 0.17) exhibit a single phase with an orthorhombic perovskite structure (Pnma). Furthermore, to understand better the thermodynamical properties of the present system, ERIM is developed and applied to study the specific heat for these compounds over a wide range of temperature. The trends of variation of computed thermodynamical and transport properties have shown remarkable good agreement with corresponding experimental data.

Investigation of magnetic properties of Sm0.55Sr0.45MnO3

In this paper, we report the enhancement of metal – insulator transition temperature (TMI) induced by magnetic field confirms the MR phenomenon. The polycrystalline Sm0.55Sr0.45MnO3 were synthesized using solid state reaction route. The XRD patterns using Full Prof Rietveld analysis shows that the sample has single phase nature without any detectable impurity. The SEM micrograph carried to observe the grain morphology and four probe resistivity measurements using with superconducting magnet to investigate the electrical behaviour. The sharp value of temperature coefficient of resistance (TCR) of 11% is used for infrared bolometric sensors.

Effect of Ag substitution on the structural and magnetic properties of Sm0.55Sr0.45MnO3 (x = 0, 0.15) system

We report the structural and magnetic properties of Ag substituted Sm0.55Sr0.45MnO3 (x = 0, 0.15) synthesized via solid state reaction method. The XRD patterns using Full Prof Rietveld analysis shows that the samples have single phase nature without any detectable impurity. SEM results shows that the grain size increases upto sharper instant. The magnetic studies reveals Neil temperature (TN) and Curie Temperature (Tc) get decreased with the lowering of temperature. The hysteresis loss which is dominant in pure sample disappears in Ag doped one. This shows that Ag helps in achieving the homogeneity thereby decreasing the disorder.

Transport properties of Ag doped Pr0.67Sr1−xAgxMnO3

We have synthesized and investigated the effect of Ag doping at x = 0 and 0.10 in Pr0.67Sr1−xAgxMnO3 via solid state reaction route. The Rietveld refinement of XRD data shows that these compounds crystallize in an orthorhombic structure with Pnma space group. On increasing the Ag content to x = 0.10, a linear variation in unit cell volume and lattice parameters is observed. The temperature dependent zero-field and in-field resistivity has been measured between 5 K to 300 K. The samples show a systematic variation in metal to insulator transition temperature and a large magnetoresistance (MR) is also observed with maxima at TMI. The highest value of Temperature Coefficient of Resistance (TCR) % has been observed by us for the first time.

Structural, transport and elastic properties of LaTiO3

The thermophysical properties such as structural, transport and elastic properties of the orthorhombic perovskite-type titanate system, LaTiO3 have been explored in detail for the first time by applying extended rigid ion model (ERIM). LaTiO3 has been subject of recent interest because of the variety of attractive behaviors, including a metal-insulator transition, spin-charge-orbital ordering and high-temperature superconductivity. LaTiO3 has been suggested to have promising scientific and technological applications. The theoretically computed thermophysical properties of LaTiO3 compound are in good agreement with the available results.