Theory of ferromagnetism inCeCo5

Electronic-structure calculations for ${\mathrm{CeCo}}_5$ in the hexagonal ${\mathrm{CaCu}}_5$ structure and, for comparison, for the isostructural compounds ${\mathrm{YCo}}_5$ and ${\mathrm{LaCo}}_5$ are reported. It is shown that the anomalous properties of ${\mathrm{CeCo}}_5$ can be understood as due to itinerant 4f states, in particular its reduced magnetic moment relative to ${\mathrm{YCo}}_5$ and ${\mathrm{LaCo}}_5$. An important concept in the electronic structure of ${\mathrm{CeCo}}_5$ is the hybridization between the 3d states of cobalt and the 4f states of cerium. With spin-orbit coupling included in the calculation, good agreement with experiment for the total magnetic moment is achieved. A non-negligible 4f magnetic moment composed of both spin and orbital contributions is found on the cerium site. This manifests the existence of itinerant 4f magnetism in this compound. Common to all three compounds are the quite large orbital moments on the cobalt sites.