Summerfield scaling model and conduction processes defining the transport properties of silver substituted half doped (La–Ca) MnO3 ceramic

Experimental measurements and numerous theoretical models have been employed to comprehend the dynamics of charge carriers in manganite system. The present work highlights the electrical transport of La0.5Ca0.4Ag0.1MnO3 compound in the temperature range [80 K–700 K]. It is found that the conductivity spectra of the studied sample present a double Jonscher variation, universal Jonscher evolution and Drude variation respectively for low, intermediate and high temperature ranges. The temperature dependence of the frequency exponent confirms the efficiency of the quantum mechanical tunneling, the non-overlapping small polaron tunneling and the correlated barrier hopping mechanisms at separated dispersive regions. DC conductivity analysis confirms the semiconductor behavior of the studied sample. Then, the transport properties have been explained in term of a thermally activated small polaron hopping and Mott-variable range hopping processes respectively at high and low temperature sides. Also, the disorder energy is predicted to decrease with rising frequency which could be due to variation in the separation path between the hop centers. Moreover, Greaves variable range hopping model is the suitable one that describes the transport properties in the intermediate temperature range. The scaling approach indicates that the time temperature superposition principle is valid in the temperature side [180 K–360 K].

Usefulness of theoretical approaches and experiential conductivity measurements for understanding manganite-transport mechanisms

Gd3+-doped lead molybdato-tungstates with the chemical formula of Pb1−3x□xGd2x(MoO4)1−3x(WO4)3x (where x = 0.0455, 0.0839, 0.1430, corresponding to 9.53, 18.32, 33.37 mol% of Gd3+, respectively, as well as □ denotes cationic vacancies) were successfully synthesized via combustion route. The XRD and SEM results confirmed the formation of single-phase, tetragonal scheelite-type materials (space group I41/a) with the uniform, spherical and oval grains ranging from 5 to 20 µm. Individual grains are strongly agglomerated into big clusters with the size even above 50 µm. The magnetic measurements as well as the Brillouin fitting procedure showed paramagnetic state with characteristic superparamagnetic-like behaviour and the short-range ferromagnetic interactions. The electrical and broadband dielectric spectroscopy studies revealed insulating properties with the residual electrical n-type conduction of 2×10−9 S/m and low energy loss (tanδ ≈ 0.01) below 300 K. Dielectric analysis showed that no dipole relaxation processes in the Gd3+-doped materials were observed. A fit of dielectric loss spectra of Gd3+-doped samples by sum of the conductivity and the Havriliak-Negami, Cole-Cole, and Cole-Davidson functions confirmed this effect.

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Combustion synthesis, structural, magnetic and dielectric properties of Gd3+-doped lead molybdato-tungstates

Transport properties of La0.5Ca0.1Ag0.4MnO3 have been studied. The dynamics of the charge carriers are studied based on scaling approaches. La0.5Ca0.1Ag0.4MnO3 ceramic reveals various conduction mechanisms. The compound exhibits a semiconductor behavior. The conductivity appears temperature independent beyond Tsat = 560 K. At low temperatures, the transport of charges is governed by the activation of the VRH mechanism. Greaves-VRH is the best model that describes the transport properties in the intermediate temperature interval. Beyond θD/2 temperature, the conductivity is thermally activated confirming the validity of Mott theories. Jonscher law explains the transport properties below 320 K. The dynamic regions are investigated in term of an activated CBH process and a nearly constant loss. Beyond T = 340 K, the conductivity is fitted using the Drude model. Also, the validity of the TTSP principle is confirmed using scaling approaches. Corrected Summerfield scaling confirms the presence of inter-ionic Coulomb interactions.

Dynamics of charge carriers in doped manganite based on conductivity measurements and theoretical models

Composites (1 − x)La0.7Ca0.3MnO3/xLa0.7Sr0.2Ca0.1MnO3: Electrical transport properties and enhancing of low-field-magnetoresistance and colossal magnetoresistance

Junfeng Li

Papers

Electrical transport properties and enhanced broad-temperature-range low field magnetoresistance in LCMO ceramics by Sm2O3 adding

Improvement of electrical and magnetic properties in La0.67Ca0.33Mn0.97Co0.03O3 ceramic by Ag doping

Enhanced temperature coefficient of resistance and magnetoresistance of Co-doped La0.67Ca0.33MnO3 polycrystalline ceramics

Large temperature coefficient of resistance and magnetoresistance of La0.71Ca0.29Mn1-xCoxO3 polycrystalline ceramics

Electrical properties and enhanced low-field magnetoresistance of Mn2O3-added La0.7Ca0.3MnO3 ceramics