Anchit Modi

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.

MoB2 Driven Metallic Behavior and Interfacial Charge Transport Mechanism in MoS2/MoB2 Heterostructure: A First-Principles Study

We have performed the density functional theory calculations on heterostructure (HS) of MoS2 and MoB2 monolayers. The aim of this study is to assess the influence of MoB2 on electron transport of adjacent MoS2 layer. In present investigation we predict that the electronic properties of MoS2 monolayer is influenced by 4d-states of Mo in MoB2 monolayer. Whereas, the B atoms of MoB2 and S atoms of MoS2 exhibit overlapping of intermediate atomic orbitals thereby collectively construct the interfacial electronic structure observed to be metallic in nature. From charge density calculations, we have also determine that the charge transfer is taking place at the interface via B-2p and S-3p states. The bonds at the interface are found to be metallic which is also confirmed by adsorption analysis. Thermoelectric performance of this HS is found be in good agreement with available literature. Low Seebeck coefficient and high electrical conductivity further confirms the existence of metallic state of the HS.

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...

Structural and transport properties of Nd0.6Sr0.4CoO3 compound

A Systematic investigation of Nd0.6Sr0.4CoO3 compound have been undertaken synthesized by the conventional solid state reaction method mainly to understand the response of structural, microstructural, thermal and electrical transport properties. The structural parameters obtained using Rietveld refinement of X-ray diffraction data which showed perovskite structure having orthorhombic (Pbma) symmetry without any detectable impurity phase. The temperature dependent resistivity study indicates the semiconductor behavior and favored the small poloran hopping conduction model. The Seebeck coefficient (S) of the pristine sample demonstrates positive value for entire temperature range.

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 Hexagonal YMn 0.9 Ru 0.1 O 3 Compound

We report that the polycrystalline hexagonal YMn0.9Ru0.1O3 compound can be synthesized by using conventional solid state reaction method at a sintering temperature of 128000. The reflections/diffraction peaks observed in the XRD measurements matched exactly with standard (JCPDS) data for the hexagonal crystal structure of YMnO3 without any extra peaks due to impurities. The dc electrical measurements of the as prepared YMn0.9Ru0.1O3 compound have been carried out below room temperature down to the minimum possible. The electrical measurement of the Ru doped YMnO3 compounds reveal that the resistivity is suppressed with the addition of the ruthenium content and a consistent increase in the resistivity have been witnessed with decreasing temperature. In generalized sense the observed resistivity versus temperature behavior in the studied compounds suggests the induction semiconductor-like character in the material.KeywordsXRD, Electrical resistivity, Manganites

Effect of chromium doping on the resistivity behavior of gadolinium manganite

Systematic investigation of structure and resistivity behaviour of GdMnO3 with 20% Cr doping has been undertaken that papered by conventional solid state reaction method. Upon Cr doping on the Mn site the lattice parameters and unit cell volume were reduced due to slight difference between the ionic radii of Cr3+ and Mn3+ compare with Pure GdMnO3 (according to JCPDS: 25-0337). The Cr-doped manganites exhibit a large variation in resistivity values. Cr3+ doping makes the material to exhibit a semiconductor behavior, for which the electronic transport can be explained by small polaron hopping (SPH) model.

Structural and transport properties of orthorhombic GdMnO3

We report structural and transport properties of the polycrystalline orthorhombic GdMnO3 compound synthesized by using conventional solid state reaction method. The XRD pattern reveals the single phase formation of the reported compound in orthorhombic crystal structure with space group Pbnm (JCPDS: 25-0337). The temperature dependent resistivity study indicates the highly resistive nature of the compound especially in the low temperature region. The effect of low temperature magnetic ordering can be clearly understood from the resistivity versus temperature plot. The calculated activation energy by using Arrhenius equation fitting are found slightly lesser than the reported value which indicates the lesser dense nature of the prepared compound.

STRUCTURAL PROPERTIES OF CHROMIUM DOPED GADOLINIUM MANGANITES

The Systematic investigation of structural behaviour of GdMn1-xCrxO3 (x=0, 0.1, 0.2) has been undertaken which are synthesized by conventional solid state reaction method. All the XRD reflection lines were successfully indexed according to orthorhombic perovskite structure with space group: pbnm (62). Upon chromium (Cr) doping on the Mn site the unit cell volume has reduced due to slight difference between the ionic radii of Cr3+ and Mn3+ compare with Pure GdMnO3. The relation between lattice parameter infer that all the samples have O´ type orthorhombic structure which is highly distorted perovskite structure but increasing the Cr concentration the orthorhombic distortion decrease that deduce the non John Teller nature of these samples.

ELECTRONIC TRANSPORT MECHANISM IN YMn0.8Ru0.2O3 COMPOUND

A single phase polycrystalline hexagonal YMn0.8Ru0.2O3 compound with space group P63cm (25-1079) have been synthesized by using solid state reaction method at sintering temperature 1280°C. The detailed low temperature electrical properties were evaluated over a broad range of temperature. The temperature dependence of the dc resistivity at low temperature reveals the semiconducting 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* ~ 1.05 × 106K and finally the density of state at Fermi level N(EF) is calculated to be ~ 5.6 × 1019 eV−1 cm−3.