Lithium substitution in LaMnO3:: Synthesis, structure, and properties of LaMn1-xLixO3 perovskites

LaMn1-x LixO3 perovskites have been synthesized by a flux method using LiCl, Substitution of Li+ creates mixed-valent manganese according to the formula LaMn1-3x3+Mn2x4+ Li-x(+) O-3, for 0.10 less than or equal to x less than or equal to 0.20. At low values of x, additional vacancies are found on the perovskite A and B sites, All the members crystallize in the rhombohedral (R-3c) perovskite structure and are semiconducting with no long-range magnetic order. The samples show spin-glass-like short-range magnetic correlations at low temperatures and Curie-Weiss behavior above ca, 150 K. The x = 0.05 and 0.10 samples show a magnetoresistive effect of similar to 90% at 50 K and 8.5 T. The effect of Li+ substitution in LaMnO3 cannot be explained on the basis of a simple percolation model. (C) 2001 Academic Press.