Phase diagram on La1-xCaxMnO3

By means of different experimental techniques as resistivity, magnetic susceptibility and specific heat we present a detailed phase diagram of the La1-xCaxMnO3 system, with special detail in the area of high Ca doping (charge-ordering, i.e. 0.5 < x < 0.8). In this concentration range three different transitions are observed. At low temperature the system ordered antiferromagnetically at temperatures between 100 and 150 K. Later, the charge ordering (CO) transition is observed between 200 and 250 K. Finally, at high temperature (300-350 K), in this high Ca concentration range, a new phase transition is present, probably related to the charge localisation (CL). This later transition is clearly observed as a broad weak peak in the specific heat, and coincide with the deviation of the Curie-Weiss behaviour in the magnetic susceptibility. (C) 1999 Elsevier Science B.V. All rights reserved.