Characteristics of magnetic order in perovskite manganites La1-xCaxMnO3

Solid solutions of the system La1-xCaxMnO3 are synthesized, and their magnetic and electrical properties are investigated. As x is increased, the crystal lattice changes symmetrically from an orthorhombic (x = 0 and x = 0.8) to a cubic structure (0 < x less than or equal to 0.6 and x = 1). Nonstoichiometric LaMnO3 and compositions with a low Ca content (0 < x < 0.4) are collinear ferromagnets. A metal-insulator transition is observed in them near the Curie temperature. Compositions with 0.6 less than or equal to x less than or equal to 0.9 exhibit a semiconductor-type conductivity and an unusual temperature behavior of the magnetization and the susceptibility with very distinct Curie and Neel temperatures. The magnetic properties of the solid solutions are explained on the basis of the model of ferro-antiferromagnetic phase separation. (C) 1999 American Institute of Physics. [S1063-7761(99)01211-1].