Absence of itinerant ferromagnetism in a cobalt-based oxypnictide

We report a layered transition-metal-ordered oxypnictide Sr₂CrCoAsO₃. The new material was synthesized by solid-state reactions under vacuum. It has an intergrowth structure with a perovskite-like Sr₃Cr₂O₆ unit and ThCr₂Si₂-type SrCo₂As₂ block stacking coherently along the crystallographic c axis. The measurements of electrical resistivity, magnetic susceptibility, and specific heat indicate metallic conductivity from the CoAs layers and short-range antiferromagnetic ordering in the CrO₂ planes. No itinerant-electron ferromagnetism expected in CoAs layers is observed. This result, combined with the first-principles calculations and the previous reports of other CoAs-layer-based materials, suggests that the Co$-$Co bondlength plays a crucial role in the emergence of itinerant ferromagnetism.