Insight on Hole-Hole Interaction and Magnetic Order from Dichroic Auger-Photoelectron Coincidence Spectra

The absence of sharp structures in the Auger line shapes of partially filled bands has severely limited the
use of electron spectroscopy in magnetic crystals and other correlated materials. By a novel interplay of
experimental and theoretical techniques we achieve a combined understanding of the photoelectron,
Auger, and Auger-photoelectron coincidence spectra (APECS) of the antiferromagnetic CoO. A recently
discovered dichroic effect in angle resolved (DEAR) APECS reveals a complex pattern in the Auger line
shape, which is here explained in detail, labeling the final states by their total spin. Since the dichroic
effect exists in the antiferromagnetic state but vanishes at the Ne´el temperature, the DEAR-APECS
technique detects the phase transition from its local effects, thus providing a unique tool to observe and
understand magnetic correlations where the usual methods are not applicable.