Electronic structure of thin cobalt film on W(1 1 0) by spin-polarized two-electron spectroscopy

The spin-dependent electronic structure of a 3 monolayer (ML) Co film on W(1 1 0) was studied using low-energy spin-polarized two-electron spectroscopy. The primary electron with spin projection perpendicular to the scattering plane impinged onto the sample and two-electrons resulting from its collision with a valence electron of the target were detected in coincidence using position sensitive detectors and time-of-flight technique for measuring momenta of both electrons. The momentum distributions I(k0, k1, k2) of correlated electrons were measured for parallel (I+) and anti-parallel (I−) orientations of the majority spin projection of the sample and for the incident beam polarization at various primary energies in the range (9 − 27) eV. Energy – and momentum-conservation laws in the scattering event allow the valence electron involved in the collision to be located in the energy–momentum space of the valence band. The measured distributions are presented in the form of the asymmetry A = (I+ − I−)/(I+ + I−). For symmetric detection of correlated electron pairs the asymmetry of the binding energy spectrum represents the spin-asymmetry of the Bloch spectral function in the centre of the Brillouin zone. This asymmetry reaches −26% just below the Fermi energy and indicates the dominance of the minority states in this region. The measurements at two opposite magnetizations perpendicular to the scattering plane were performed to map the exchange correlation and spin–orbit interaction in energy–momentum space of the cobalt film valence band.