The electronic and magnetic properties of cobalt-based layered oxypnictides, LaCoOX (X = P, As), are investigated. LaCoOP and LaCoOAs show metallic type conduction with room temperature resistivities of ~2×10 -4 Ω·cm, and the Fermi edge is observed by hard x-ray photoelectron spectroscopy. Ferromagnetic transitions occur at 43 K for LaCoOP and 66 K for LaCoOAs with spontaneous magnetic moments of 0.33 µ B and 0.39 µ B extrapolated to 0 K, respectively. Above the transition temperatures, the magnetic susceptibility exhibits a large temperature dependence. Provided that this temperature dependence follows the Curie-Weiss law, enhanced magnetic moment values of ~2.9 µ B for LaCoOP and ~1.3 µ B for LaCoOAs are obtained. X-ray magnetic circular dichroism (XMCD) is observed at the Co L 2,3 -edge, but not at the other edges. The calculated electronic structure shows a spin polarized ground state with a magnetic moment of 0.52 µ B , ~95% of which is localized on the Co ions. These results indicate that LaCoOX are itinerant ferromagnets and suggest that their magnetic properties are governed by spin fluctuation. PACS

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