A direct two-dimensional comparison of magnetic circular dichroism and magnetic linear dichroism in ultraviolet photoemission spectroscopy

Abstract

The angular dependence of magnetic dichroism in photoemission (MDAD) from valence bands is more complicated than that from core levels. It gives access to spin-resolved information about the bands involved in the photoexcitation process. By using a unique ellipsoidal-mirror analyzer, we are able to observe MDAD from valence bands as a two-dimensional image, which gives a direct view of their angular dependence over a large slice through the Brillouin zone. In this work we have investigated Co films grown on a Cu(001) substrate. By using either circularly polarized light or linearly polarized light at a photon energy of 21 eV, magnetic circular dichroism and magnetic linear dichroism (MLD) from the Fermi edge shows different angular dependencies. This is due to the different excitation processes involved with the different light polarizations and it reflects the symmetry of the 3d bands of the Co. Furthermore, we also find that the sign of the MLD can change if differing initial states are involved. First principles calculations of Co bands and their photoelectron angular distributions with the different light polarizations will be presented. This shows that dichroism in valence band photoemission can provide valuable additional information on the electronic and magnetic properties of ultrathin films.