ИСТИНА

The electronic state and the local environment of the matrix iron ions and the impurity tin ions in the orthoferrites Gd1-xCaxFe0.997Sn0.003O3-w (x = 0; 0.2), synthesized by the citrate sol-gel method, were characterized by Mossbauer spectroscopy on 57Fe and 119Sn nuclei. The antiferromagnetic ordering temperature were determined as TN = 608 K. It is established, that in the sample Gd0.800Ca0.200Fe0.997Sn0.003O2.98, obtained by annealing in air, the deficit of the positive charge is compensated by oxidation of Fe3+ ions to Fe4+(5+). It is shown, that after annealing in H2 all iron ions are in the oxidation state +3; so the charge compensation is because of the formation of oxygen vacancies.