Controlled Phase separation In LaCaMnO

P. LEVY; FRANCISCO PARISI,; GRISELDA POLLA,; D VEGA,; G LEYVA, A; H LANZA,

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

The American Physical Society

Lugar: http://prola.aps.org/abstract/; Año: 2000 vol. 62 p. 6437 - 6437

0163-1829

A systematic study of phase separation effects in polycrystalline La 0.5 Ca 0.5 MnO 3 obtained under different thermal treatments is reported. Samples with average grain size ranging from 200 to 1300 nm were studied.Magnetic and electrical measurements show quantitative differences among samples in their low-temperaturebehavior, indicating that the fraction of the ferromagnetic ~FM! phase gradually decreases as the grain sizeincreases. Percolation of the FM phase in samples with a small fraction of this phase suggests that grainboundaries play a distinctive role in the spatial distribution of coexisting phases. The defective structure at thegrain surface could explain the local inhibition of the antiferromagnetic charge ordered phase, an effect that isgradually removed with increasing grain size. Qualitative agreement of the data with this description is found.This effect is also found to be highly dependent on the oxygen content of the samples and its spatialdistribution.