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In this research we present the synthesis and characterization study of powder and bulk samples of La0.67Ca0.33MnO3-α (LCMO) manganites, prepared by solid state reactions. The analysis of the reaction was done by Thermogravimetry (TGA) and Differential Thermal Analysis (DTA) measurements, in air atmosphere with temperature increase of 10°C/min from 23°C to 900°C. In the TGA and DTA curves we observed different lost weight regions between 336°C and 705.32°C, due to decomposition of the precursor. Above this latter temperature, the reaction as stable. The final product was 85.17% of the starting mixture. Powder XRD measurements were fitted using Rietveld method. The observed crystalline structure was orthorhombic. The chemical composition by EDX measurements showed the phase of compound. The manganese ions (Mn3+ y Mn4+) content was determined by iodometric titration method. Finally, in the magnetometry measurements using SQUID with external applied field of 400 gauss and cooling without field from 300K to 20K, Curie temperature in the sample was measured (TC-251K). [ABSTRACT FROM AUTHOR]

Manganites with La2/3Ca1/3Mn1-yFeyO3 (y = 0.01 y 0.03) composition were fabricated, by a solid-state reaction in powder and bulk form, using α-Fe2O3, hematite as a precursor, enriched with 95.06% of 57Fe. The hyperfine parameters obtained from the fits of Mössbauer spectrums, show the presence of Fe3+ in octahedral sites of the compounds. The c-axis parameters calculated from the fits to XRD measurements were (7.686(2) Å and 7.670(3) Å for 1 and 3% of Fe, respectively. Neither impurities nor additional phases were observed. Magnetization measures in function of temperature show a small reduction of transition temperature and magnetization when concentration of Fe increases. [ABSTRACT FROM AUTHOR]