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Register a new userInfluence of Al-doping on the structural, magnetic, and electrical properties of La$_{1-x}$Ba$_x$Mn$_{1-x}$Al$_x$O$_3$ ($0leq x leq 0.25$) manganites
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Added by
Ismaeil Abdolhosseini Sarsari
Publication date
2016
fields
Physics
and research's language is
English
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We have studied the effect of Al doping on the structural, magnetic and electrical properties of La$_{1-x}$Ba$_x$Mn$_{1-x}$Al$_x$O$_3$ ($0leq x leq 0.25$) manganite, annealed in two 750$^oC$ and 1350$^oC$ temperatures. The XRD analysis shows that the structures in all samples have single phase rhombohedral structure with R$bar{3}$c space group. The unit cell volume almost decrease with increasing the Al doping in all samples. The grain growth with increasing annealing temperature and Al doping also have been studied. We observed that, T$_c$ temperature decreases when the Al ion substitute in Mn ion site. The magnetic study of the samples via magnetic susceptibility results in Griffiths and spin-glass phase for samples doped with aluminium. Along the resistivity measurement results, the $T_{MIT}$ (metal-insulator) transition temperatures decrease and the system become an insulator. The insulator-metal transition occurs for L0 sample in near 165K, while this transition is weak for H0 sample due to oxygen non-stoichiometry.Using three models viz. 1. Adiabatic small polaron hoping, 2.Variable range hopping, and 3. Percolation model, the resistance have been studied.
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We report the temperature and magnetic field dependence of transport properties in epitaxial films of the manganite La$_{1-x}$Ca$_{x}$MnO$_{3}$ in the overdoped region of the phase diagram for $x > 0.5$, where a charge--ordered (CO) and an antiferromagnetic (AF) phase are present. Resistivity, magnetoresistance and angular dependence of magnetoresistance were measured in the temperature interval $4.2 ~mathrm{K} < T < 300 ~mathrm{K}$, for three concentrations $x = 0.52, 0.58$ and $0.75$ and in magnetic fields up to 5 T. The semiconductor/insulator--like behavior in zero field was observed in the entire temperature range for all three concentrations textit{x} and the electric conduction, at lower temperatures, in the CO state obeys 3D Motts variable--range hopping model. A huge negative magnetoresistance for $x = 0.52$ and $x = 0.58$, a metal--insulator transition for $B > 3 ~mathrm{T}$ for $x = 0.52$ and the presence of anisotropy in magnetoresistance for $x = 0.52$ and $x = 0.58$ show the fingerprints of colossal magnetoresistance (CMR) behavior implying the existence of ferromagnetic (FM) clusters. The declining influence of the FM clusters in the CO/AF part of the phase diagram with increasing $x$ contributes to a possible explanation that a phase coexistence is the origin of the CMR phenomenon.
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