Monolayer resolved oscillating hyperfine fields in epitaxial face-centered-tetragonal Co(001) films.

Ultrahigh-quality thin fct-Co films grown on Cu(001) have been investigated by 59Co nuclear magnetic resonance. The influence of the spin-dependent electron scattering at the interfaces is observed for at least four Co atomic layers from the interface with monolayer resolution. An oscillatory effect on the Co hyperfine field with a period of several monolayers is measured, corresponding to the oscillating conduction electron polarization.

Band structure and density of States effects in co-based magnetic tunnel junctions.

Utilizing Co/Al(2)O(3)/Co magnetic tunnel junctions with Co electrodes of different crystalline phases, a clear relationship between electrode crystal structure and junction transport properties is presented. For junctions with one fcc(111) textured and one polycrystalline (polyphase and polydirectional) Co electrode, a strong asymmetry is observed in the magnetotransport properties, while when both electrodes are polycrystalline the magnetotransport is essentially symmetric. These observations are successfully explained within a model based on ballistic tunneling between the calculated band structures (density of states) of fcc-Co and hcp-Co.