Charge ordering and magnetotransport transitions in Sm1/3Sr2/3FeO3-delta

Charge ordering (CO) between Fe3+ and Fe5+ species and magnetotransport tra nsition have been shown for the first time in the perovskite Sm1/3Sr2/3FeO3 -delta by electron diffraction microscopy, by Fe-57 Mossbauer spectroscopy, and by measurements of transport and magnetic properties. This compound is charge ordered at T-CO = 110 K, which is significantly lower than the temp erature T-N = 150 K of the magnetotransport transition, A charge disproport ionation 2Fe(4+) <-> Fe3+ + Fe5+ is evidenced by Mossbauer spectroscopy. Th e electron diffraction study shows the coexistence of orthorhombic and rhom bohedral-type domains. A comparison with the other lanthanides (La, Pr, Nd) is also made. This suggests that the size of the Ln(3+) ion is not the onl y parameter which governs the charge ordering in these perovskites, but the oxygen stoichiometry, which influences the Fe5+ formation, may also play a role in the CO phenomenon. (C) 2000 Academic Press.