Structural and electrical properties in La1-xLixMnO3

Li-substituted perovskites La(1-x)Li(x)NnO(3) (LLMO; 0.05 <= x <= 0.25) were investigated by X-ray diffraction, electric resistivity and magnetoresistance (MR) measurements. All samples show a rhombohedral structure (space group R (3) over barc) at room temperature. The cell parameters a, c and the unit cell volume decrease with increasing Li content. A metal to insulator transition is observed for all the samples. The metal to insulator transition temperature T-MI appears of all the samples shifts to a lower temperature and the resistivity increases with increasing Li content. The resistivity data in the metallic region (below TAN) is well fitted (for x <= 0.15) with the expression corresponding to electron-electron scattering mechanism. The high temperature (T > theta(D)/2, theta(D) is Debye temperature) resistivity data, both in presence and in absence of magnetic field, is found to be quite well described by the adiabatic small polaron-hopping model. The lower temperature (between T-MI and theta(D)/2) resistivity data of all the samples is found to be in accordance with the variable range hopping model. A nearly constant MR=50% with the application of magnetic field of 0.5 T over the measured temperature zone between 313 and 79K was observed for low doping Li-content(x <= 0.10), which is very beneficial for practical applications. (C) 2011 Elsevier B.V. All rights reserved.