The temperature dependence of the resistivity
(ρ) and magneto-resistance (MR) effect of La1−xLixMnOy
(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–semiconductor
(M–S) transition for all compositions. In addition, the replacement
of the Li-substitution results in a reduction of
the transition temperature Tms and increases ρ. 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 (Eρ)
in the semiconductor region.