Lithium Substitution in LaMnO_3: Synthesis, Structure, and Properties of LaMn_(1-x)Li_xO_3 Perovskites

摘要

LaMn_(1-X)Li_xO_3 perovskites have been synthesized by a flux method using LiCl. Substitution of Li~+ creates mixed-valent manganese according to the formula LaMn_[(1-3x)~(3+)]Mn_[(2x)~(4+)]Li_(x~+)O_3, for 0.10 < = < = 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 approx 90% at 50 K and 8.5 T. The effect of Li~+ substitution in LaMnO_3 cannot be explained on the basis of a simple percolation model.