Spin-resolved electronic band structure of fct-cobalt (100) (abstract)

Abstract

The spin-polarized electronic structure of the fcc high-temperature modification of cobalt has not been investigated yet, because of the experimental difficulties of photoemission at high temperature. We stabilized fcc Co by molecular-beam epitaxy on a Cu(100) substrate with large, atomically flat terasses (0.5–1 μm wide) as revealed by STM. The structure of the layers was studied by LEED and MEED, showing a tetragonal distortion of the fcc lattice perpendicular to the (100) surface plane. The dispersion of the exchange split bands perpendicular to the surface was determined for a 5-monolayer-thick sample (tetragonal distortion on average 4%–5%) by spin- and momentum-resolved photoemission. The results are compared to two relativistic spin-polarized band-structure calculations for fcc cobalt. Somewhat surprisingly, even a 5-ML-thick sample shows three-dimensional dispersion in good agreement with the calculations, as far as the average exchange splitting (1.2±0.2 eV), and the symmetry character of the bands is concerned. There are, however, some systematic deviations of minority bands near the Fermi energy which are attributed to the tetragonal compression.