Mesoscopic and Condensed Matter Physics

Biography

Biography: L. N. Singh

Abstract

Transport behavior and magnetoresistance in solgel prepared Nd_0.7Sr_0.3-xBa_xMnO₃ (0≤x≤0.3) nanomanganite system have been investigated in temperature range 10 -330 K. The composition and structural properties were studied at various concentrations by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). X-ray diffraction (XRD) pattern confirms the single phase nature of the samples with orthorhombic crystal symmetry. The average A-site ionic radii which is directly related to tolerance factor and size variance, plays a vital role in magnetotransport properties. The metal-insulator transition temperature, T_MI, shifts toward low temperature with increasing Ba substitution from 205 to 95 K and shows semiconducting like behavior at low temperature. It is shown that the correlated polaron model accounts for the temperature dependence resistivity and magnetoresistance in the entire temperature range. The number of charge carriers, n decreases as Ba²⁺ ion concentration increases. The small polaron binding energy, e_p, is found to decrease as Ba²⁺ ion concentration increases. The increase in the thermally assisted activation energy, U₀, is observed as the system varies from Sr- to Ba- substitution. The number of charge carriers, n, is decreases as Sr²⁺ ion concentration decreases which is responsible for the increase in resistivity values.