Magnetic interactions in perovskite compounds of the type La1–xSrxMO3–δ (where M was a 3d transition element such as Mn or Fe) were presumed to arise through a super exchange between 3d electrons of the magnetic ions via O orbitals. The magnetic structure of La0.6Sr0.4FeO3–δ was studied with neutron diffraction. Oxygen vacancies were created by annealing samples under various gases including N2, air and mixtures of CO/CO2. All La0.6Sr0.4FeO3–δ compounds maintained the rhombohedral structure (R¯3c). The air- or O-annealed samples had almost no O vacancies while those made in a reducing atmosphere contained 7 to 11% of O vacancies. The rhombohedral distortion decreased in the reduced samples. All the samples exhibited antiferromagnetic ordering at room temperature, although a small ferromagnetic moment may also be present. Samples with few or no O vacancies exhibited a room-temperature magnetic moment of about 1.4µB at the Fe site while those having more than 7% of O vacancies exhibited a moment of about 4.0µB. Magnetization measurements revealed a much higher magnetic ordering temperature in samples with O vacancies.

Effect of Oxygen Vacancies on the Magnetic Structure of the La0.6Sr0.4FeO3–δ Perovskite - a Neutron Diffraction Study. Z.Chu, W.B.Yelon, J.B.Yang, W.J.James, H.A.Anderson, Y.Xie, S.K.Malik: Journal of Applied Physics, 2002, 91[10], 7938-40