Interpretation of magnetic dichroism in angle-resolved UV photoemission from valence bands

Magnetic dichroism in angle-resolved UV photoemission is a simple extension of conventional photoemission experiments which is sensitive to the effects of spin—orbit coupling in itinerent electron ferromagnets which ultimately determine the magnetocrystalline anisotropy. A qualitative model of the magnetic dichroism arising from bulk-band transitions allows experiments to be interpreted with reference to widely available, approximate band-structure calculations which ignore spin—orbit coupling. Strong hybridization of initial state bands via spin—orbit coupling, gives a plus/minus feature in the dichroism, and (usually) corresponds to what is conventionally understood as magnetic dichroism in angular distribution (MDAD) of photoelectrons. Spin and parity mixing in time-reversed LEED photo-electron states, give rise to a feature of single sign in the dichroism, and (usually) correspond to what is conventionally understood as spin-dependent surface transmission. These results suggest that the technique can be used to follow the dispersion and hybridization of closely spaced initial state bands which are poorly resolved in conventional photoemission, and to infer the spatial symmetry and spin of the bands without recourse to sophisticated photoemission calculations. Under favourable conditions, the spin—orbit splitting or the exchange splitting of bands can be determined.