Itinerant ferromagnetism in the layered crystals<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mtext>LaCoO</mml:mtext><mml:mi>X</mml:mi><mml:mspace width="0.3em"/><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mi>X</mml:mi><mml:mo>=</mml:mo><mml:mtext>P</mml:mtext><mml:mo>,</mml:mo><mml:mtext>As</mml:mtext></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>

The electronic and magnetic properties of cobalt-based layered oxypnictides, $\text{LaCoO}X(X=\text{P},\text{As})$, are investigated. LaCoOP and LaCoOAs show metallic type conduction with room-temperature resistivities of $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\ensuremath{\Omega}\text{ }\text{cm}$, 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 $0.33{\ensuremath{\mu}}_{B}$ and $0.39{\ensuremath{\mu}}_{B}$ 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 $\ensuremath{\sim}2.9{\ensuremath{\mu}}_{B}$ for LaCoOP and $\ensuremath{\sim}1.3{\ensuremath{\mu}}_{B}$ 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 $0.52{\ensuremath{\mu}}_{B}$, $\ensuremath{\sim}95%$ of which is localized on the Co ions. These results indicate that $\text{LaCoO}X$ are itinerant ferromagnets and suggest that their magnetic properties are governed by spin fluctuation.