Oxygen stoichiometry, crystal structure, and magnetism in La₀.₅Sr₀.₅CoO₃₋δ

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We have prepared a series of polycrystalline samples La₀.₅Sr₀.₅CoO₃₋δ with 0 < δ≤ 0.21 and characterized their oxygen content, crystal structure, and magnetic properties. While the fully oxygenated samples are good ferromagnets, samples with larger δ values display increasingly broad magnetic transitions. The saturation magnetization at 5 K falls rapidly as δ increases. First principles electronic structure calculations provide insights into the magnetic behavior of the fully oxygenated compound, and the manner in which ferromagnetic ordering is affected by increasing oxygen non-stoichiometry.