INFLUENCE OF THE GRAIN-SIZE AND OXYGEN STOICHIOMETRY ON MAGNETIC AND TRANSPORT-PROPERTIES OF POLYCRYSTALLINE LA0.67CA0.33MNO3+ -DELTA PEROVSKITES/

Citation
Le. Hueso et al., INFLUENCE OF THE GRAIN-SIZE AND OXYGEN STOICHIOMETRY ON MAGNETIC AND TRANSPORT-PROPERTIES OF POLYCRYSTALLINE LA0.67CA0.33MNO3+ -DELTA PEROVSKITES/, Journal of magnetism and magnetic materials, 189(3), 1998, pp. 321-328
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Material Science","Physics, Condensed Matter
ISSN journal
0304-8853
Volume
189
Issue
3
Year of publication
1998
Pages
321 - 328
Database
ISI
SICI code
0304-8853(1998)189:3<321:IOTGAO>2.0.ZU;2-4
Abstract
Effects of grain size and oxygen stoichiometry in sol-gel and ceramics samples of La0.67Ca0.33MnO3+/-delta have been studied. Grain size (90 nm versus > 10 mu m) does not change either the Curie temperature (T- c) or the metal-insulator transition temperature (TM-I), but great dif ferences in low-field magnetoresistance are observed. These difference s have been explained by a spin polarized tunneling model for conducti on between grains. Oxygen content (delta) could be changed in La defic ient samples via an electrochemical method at room temperature (i.e., without changing grain size). We observe great differences in TM-I whe n decreasing delta, while T-c remains unchanged. Broken ways between M n ions leads to zones with ferromagnetic behavior, but inhibits conduc tivity. (C) 1998 Elsevier Science B.V. All rights reserved.