Structure and magnetism of Pr1-xSrxCoO3-δ

The structural, magnetic, and nonstoichiometric properties of the perovskite-like Pr1-xSrxCoO3-delta phase (0 less than or equal to x less than or equal to 0.80) have been studied by powder X-ray and neutron diffraction and magnetic susceptibility measurements between 5 and 295 K as well as by redox titration. In the compostion range 0 less than or equal to x less than or equal to 0.30 the structure can be described with a GdFeO3-type atomic arrangement (space group Pnma), while the structure in the composition range 0.30 < x less than or equal to 0.80 involves a lower symmetry (space group P2(1)/n). Samples with 0.10 less than or equal to x less than or equal to 0.80 exhibit ferromagnetism below a Curie temperature of less than or equal to 250 It, depending on the composition. The Pr1-xSrxCoO3-delta phase behaves as a relatively hard magnetic material. For samples prepared and cooled to room temperature in air, the oxidation state of cobalt increases linearly up to x approximate to 0.50 and stabilizes at +3.4 for higher substitution levels of Sr. On the basis of the present data, it is not possible to prove or disprove that there occurs charge ordering in Pr1-xSTxCoO3-delta. (C) 1999 Academic Press.