Phase separation in La0.5Ca0.5MnO3 controlled trough thermal treatments

A study of phase separation effects in polycrystalline La0.5Ca0.5MnO3 in sa mples with average grain size ranging from 200 to 1300 nm is reported. Magn etic and electrical measurements show that the fraction of the ferromagneti c metallic phase gradually decreases as the grain size increase. The defect ive structure at the grain surface could explain the local inhibition of th e COAFM phase, an effect that is gradually removed by grain size increase. Besides, this effect is also found to be highly dependent on the oxygen con tent and its spatial distribution. (C) 2001 Elsevier Science B.V. All right s reserved.