Interplay between 3d and 4f magnetism in CeCoPO

The ground state properties of CeCoPO, a homologue of the new high temperature superconductors LnFePnO_1-xF_x, were studied by means of susceptibility, specific heat, and resistivity measurements on polycrystals. The observation of a well defined Curie-Weiss behavior above 230 K with μ_eff=2.9μ_B and a ferromagnetic ordering below is similar to what was observed in LaCoPO and points to magnetism of the Co-3d electrons. However, the Ce-ions are on the border to magnetism with a Kondo scale of and show an enhanced Sommerfeld coefficient of .