Oxygen stoichiometry, crystal structure, and magnetism of La0.5Sr0.5CoO₃

We have prepared a series of polycrystalline samples La 0.5 Sr 0.5 CoO 3−δ with 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 behaviour of the fully oxygenated compound, and the manner in which ferromagnetic ordering is affected by increasing oxygen non-stoichiometry.