English abstract
Single-phased LaFeO, perovskite-related nanocrystalline particles were synthesized via the prolonged milling of initial oxide reactants (La-03, a-Fe 03). The formation temperature of the resulting perovskite is 400 °C lower than those at which the material is conventionally synthesized. Doping with 30% of Eutions caused a decrease in the average crystallite size; however adding 5% of Cr ions increased the average size slightly. Moreover, the Mössbauer measurements revealed that Fe ions are present in all synthesized samples. The spectrum of Lao 7Euo 3FeO; and Lao EuozFeo 95Cro050; consists of two sextets, indicating the wide distribution of particle sizes which was associated to the collective excitation model. LaFeO3 exhibited exchange bias effect with blocking temperature more than 300 K. The magnetization was found to increase drastically in the case of Lao 7Eur 3FeO3, while the magnetization of Lao 7 Euo 3Feo osCroosO; decreased. The Tight-binding calculations (TB) for energy band of LaFeO3 confirmed the semiconductor propertyGdFeO3 was prepared by milling-assisted solid state reaction. The formation temperature of a single phase was found at 900 °C for 5 h which is lower than those reported using the conventional methods. GdFe-xMn, Oz (y = 0.25, 0.20 and 0.15) was synthesized at different higher temperatures; however a successful doping was limited to some extent to y <0.15. The Rietveld refinements of XRD patterns revealed that the dopant Mn+ ions occupy Fe site. The unit cell volume decreases with increasing Mnt content.The transmission electron micrograph showed the presence of fairly irregular particles in nano scale. The broadened magnetic components in Mössbauer spectra suggest sizedependent hyperfine magnetic field. Also, the magnetization of GdFeO, was found to be 0.25 emu/g and decreased for GdFeo 80 Mno. 150; to reach 0.12 emu/g at room temperature. The zero-field-cooled (ZFC) and field-cooled (FC) magnetizations for doped compound reveal that complex magnetic transitions occur in a temperature around 220 K under constant field at H = 100 Oe.
