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    A-site Pb doping effect on structural, microstructural and magnetotransport properties of La0.5Sm0.2Ca0.3-xPbxMnO3 (x=0, 0.05, 0.10) manganite
    (Elsevier Science SA, 2021) Denbri, Fatih; Mahamdioua, Nabil; Meriche, Faiza; Koç, Nevin Soylu; Terzioğlu, Cabir; Varilci, Ahmet; Altıntaş, Sevgi Polat
    Structural, microstructural and magneto-transport properties of polycrystalline La0.5Sm0.2Ca0.3-x PbxMnO3 (x = 0, 0.05 and 0.10) samples, prepared by conventional solid state reaction, were studied. Refinement of the Powder X-ray diffractograms revealed that all the samples crystallize into orthorhombic structure with Pnma space group and the lattice parameters increase with increasing Pb content. The scanning electron microscope (SEM) micrographs show a granular character and the estimated grain sizes ranges between 10 mu m and 20 mu m. The experimental electrical resistivity and the magnetoresistance in the temperature range 20 K-250 K under magnetic field of zero and 1 Ta, have been recorded using four probe technique. The resistivity curves without magnetic field, exhibit a ferromagnetic-metallic (FM) to paramagnetic-insulating (PI) transition at TMI = 125 K, 91 K and 37 K for x = 0, 0.05 and 0.10, respectively. The magnetoresistance reaches 58% for undoped sample and decrease with Pb doping under 1T. The resistivity values increases drastically with Pb doping. These two results were explained mainly by the increase of the disorder sigma 2 and rA TMI) and for x = 0 and 0.05 samples, the resistivity curves is well fitted by a combination of the residual resistivity, weak localization and electron-electron scatterings; in addition to small polaron contribution or electron-phonon interaction respectively. In the high temperature regime T TMI, all our resistivity curves has been analyzed using adiabatic small polaron hopping model (ASPH) above theta D/2 and variable range hopping model (3D-VRH) (TMI < T < theta D/2). An attempt to use the percolation model to describe the resistivity data in the entire temperature range for both x = 0 and 0.05 samples, was established. Finally, density of state, mean hopping distance Rh and mean hopping energy Eh were calculated and discussed.
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    Investigation of magneto-transport properties of the co-doped La1.6-xPrxCa1.4-xBaxMn2O7 (x=0.2 and 0.4) double-layered manganite
    (Springer, 2021) Denbri, Fatih; Mahamdioua, Nabil; Meriche, Faiza; Altıntaş, Sevgi Polat; Terzioğlu, Cabir
    Structural and magneto-electrical transport properties of double-layered La1.6-xPrxCa1.4-xBaxMn2O7 (x = 0.2 and 0.4) manganite compounds were studied. X-ray diffraction patterns refinement shows that the samples crystallize in a tetragonal I4/mmm structure, whereas a rhombohedral structure phase with R-3-c space group is detected as a secondary phase. The electrical resistivity under 0 and 1 T exhibited a metal-insulator transition at T-MI. It is found that the rho(T) decreases with increasing Pr-Ba contents. Magnetoresistance (MR%) curves displayed a maximum value of similar to 51.69% at 63 K for the x = 0.2 sample and decreases with increasing Pr-Ba concentrations to similar to 33.44% at 64 K for x = 0.4 under 1 T. The obtained values of the temperature coefficient of resistivity for both samples have similar trend as T-MI. Below T-MI,T- rho(T = rho(0) - rho T-0.5(0.5) + rho T-2(2) + rho T-5(5) model fits well the resistivity curves which reflect a combination of the grain boundary effects, weak localization, electron-electron, and electron-phonon scattering to the electrical resistivity. Above T-MI, the non-adiabatic small polaron hopping model describes the electrical resistivity behavior in T > theta(D)/2 region. The Mott's 3D variable range hopping mechanism (3D-VRH) was found to be the most suitable mechanism for describing the high-temperature resistivity behavior between T-MI and theta(D)/2. The density of states near the Fermi level N(E-F) and mean hopping energy (E-h) of the charge carriers have been calculated from the experimental curves using Mott's 3D-VRH model. The experimental and fitting curves of the resistivity and the related results are discussed in detail.
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    Optical and magnetic properties of the La0.7RE0.1Ca0.2CrO3 (RE = Nd, Sm and Eu) orthochromite for optoelectronic and magnetic applications
    (Springer, 2023) Bouasla, Fatima Zohra; Mahamdioua, Nabil; Alonso, Jose A.; Martinez, Jose L.; Meriche, Faiza; Terzioğlu, Cabir; Altıntaş, Sevgi Polat
    The orthochromites La0.7RE0.1Ca0.2CrO3 (RE = Nd,Sm, and Eu) were prepared by solid-state reaction and the structural, microstructural, optical, and magnetic properties were investigated. The XRD revealed an orthorhombic perovskite structure. The UV–visible revealed the bandgap energy values: 2.81, 2.98, and 3.12 eV for Nd, Sm, and Eu doped samples, respectively. It is explained by the creation of the localized state. The refractive index, Urbach energy, and optical conductivity were investigated. The magnetization investigation revealed that the Ne´el temperature decreases with decreasing substituting ionic radius. Below TN, all samples exhibit weak ferromagnetic behavior due to the t-e hybridization caused by intrinsic distortions. The Nd and Sm doped samples show spin reorientation due to the exchange interaction between the Sm3?/Nd3? and Cr3?. The negative magnetization of the Nd-doped sample indicates its possible use as a volatile memory device. Regarding the Eg values, our samples could be suit able candidates for optoelectronic devices
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    Synthesis and experimental study of structure, magnetotransport properties and temperature coefficient of resistance of La0.7Ca0.18Ba0.12Mn0.95Sn0.05O3 manganite
    (Springer/Plenum Publishers, 2022) Boufigha, S.; Mahamdioua, Nabil; Denbri, Fatih; Altıntaş, Sevgi Polat; Terzioğlu, Cabir
    La0.7Ca0.18Ba0.12Mn0.95Sn0.05O3 compound has been successfully prepared by the solid-state reaction route. The structural, electrical, magnetotransport properties, as well as the temperature coefficient of resistance, were experimentally characterized and discussed. Rietveld's refinement of the X-ray diffractogram revealed that the compound crystallizes in an orthorhombic structure with a Pnma space group. The estimated crystallite size is about 43 nm. The SEM micrographs revealed the granular nature and polygonal grain shape of the sample. The electrical resistivity curves, carried out between 20 and 300 K, show a metal-to-insulator transition and an upturn at a very low-temperature range (20 K < T< 32 K). The magnetoresistance maximum value reached 23.23% at 20 K under 1 Tesla. The temperature coefficient of resistance curves exhibits a slight characteristic peak around TMI, and its value is around 1.96%. Fitting the electrical resistivity curves in the metallic region (32 K < T <= T-MI) confirms that the resistivity behavior is governed by a combination of residual resistivity, electron-electron scattering process, and electron-phonon interaction, whereas in the insulating region (T >= theta(D)/2), it is governed by adiabatical small polarons hopping.