LOW-TEMPERATURE SYNTHESIS, STRUCTURE AND MAGNETORESISTANCE OF SUBMICROMETRIC LA1-XKXMNO3+DELTA PEROVSKITES

The use of a precursor-based synthetic method, namely, the freeze-dryi ng of acetic acid solutions, allows the preparation, at temperatures a s low as 600 degrees C, of single phase perovskites in the solid solut ion series La1-xKxMnO3+delta. This soft treatment of the precursors yi elds products constituted of homogeneous nanometric particles (30-50 n m). Samples prepared at 1000 degrees C remain single phase for x = 0.0 0, 0.05, 0.10 and 0.15, and are constituted by submicrometer homogeneo us particles, without deviation from nominal stoichiometries upon heat ing. Their crystal structures were refined by the Rietveld method from X-ray powder diffraction data. Ac susceptibility, magnetization, resi stivity and magnetoresistivity measurements have allowed us to establi sh, for the first time, relevant points of the electronic phase diagra m of an alkali-metal-doped lanthanide manganate system.