Ultrathin films of FCC (001) Co and Cu: Electronic structure, photoemission, and magnetic dichroism

A relativistic Green function theory of the layer-KKR type has been applied to calculate the electronic structure and its manifestation in valence-band photoemission of ferromagnetic layer systems of the form Co/Cu/Co(001) and Cu/Co/Cu(001). The spin- and layer-resolved density of states in Co films of one to ten monolayers on Cu(001) is almost mirror symmetric with respect to the central Co plane. For Cu films on Co(001), minority spin ''quantum well states'' have constant weights in the Cu monolayers and a stronger weight in the first Co monolayer. For all systems, spin-resolved photoemission spectra mostly reflect the spin character of the initial states with modifications by spin-orbit coupling. As a consequence, the spin-averaged photocurrent by p-polarized light from films with in-plane magnetization shows a pronounced dependence on the magnetization direction, i.e. magnetic linear dichroism. For perpendicular magnetization, circularly polarized light produces sizeable magnetic circular dichroism in photoemission.