Effect of Li-Substitution on the Resistivity and Magnetoresistance of LaMnO y

The temperature dependence of the resistivity (??) and magneto-resistance (MR) effect of La_1?x Li _x MnO _y (x=0.05, 0.1, 0.15, 0.2 & 0.25 at.%) fixed valence doped compounds were studied between 80 and 320 K. X-ray powder diffraction (XRD) at room temperature shows that the samples are single phase. The resistivity of all samples with and without magnetic field shows a metal?Csemiconductor (M?CS) transition for all compositions. In addition, the replacement of the Li-substitution results in a reduction of the transition temperature T _ms and increases ??. In the magnetic field of 0.5 Tesla a large negative magnetoresistance (MR=50%) was observed, which is encouraging for potential application of colossal magnetoresistance (CMR) material at low fields. We determine the activation energy (E _?? ) in the semiconductor region.