How itinerant are 3d electrons in transition metals? A study of magnetic circular dichroism in 2p photoemission

We show how the spectral structure of the magnetic circular dichroism (MCD) in photoemission (PE) can be analysed using a sum rule for the sublevel orbital moment. For itinerant 3d metals, such as Co, Fe and Ni, the MCD in the 2p PE does not agree with a single-particle model. On the other hand, a final-state impurity model calculation gives an excellent agreement with the experimental results for the Ni 2p PE of nickel metal. This indicates that inter-configurational mixing must be taken into account to understand the detailed MCD structure in metallic systems. Vice versa, MCD-PE can help to explain the complicated behavior of electrons in correlated materials.