Ferromagnetism and metallicity in the modulated Sr1−xThxCoO3−δ oxygen deficient perovskites with x∼0.1

The Th4+ for Sr2+ substitution in SrCoO3−δ is found to be an efficient way to stabilize an oxygen deficient perovskite. The structural study reveals a Th4+ solubility limited to ∼10% so that the chemical formula, Sr0.9Th0.1CoO2.79, is obtained. The comparison to the Y3+ for Sr2+ substitution shows that a lower oxygen content is obtained for the former according to the Sr0.75Y0.25CoO2.55 formula. The higher oxygen content reached with Th4+ has a strong impact on the physical properties: Sr0.9Th0.1CoO2.79 is an itinerant ferromagnet (TC∼200 K, ρ5 K=2 mΩ cm) whereas Sr0.75Y0.25CoO2.55 is a robust insulating antiferromagnet (TN∼320 K, ρ5 K=105 Ω cm). Clearly, the substitution of a tetravalent cation for Sr2+ appears to be a promising route to synthesize SrCoO3−δ itinerant ferromagnets without the use of high oxygen pressure nor electrochemical oxidation.