Stable and metastable structures of Co on Cu(001): An ab initio study

We report results of density-functional theory calculations on the structur al, magnetic, and electronic properties of (1 x 1) structures of Co on Cu(0 01) for coverages up to two monolayers. In particular we discuss the tenden cy towards phase separation in Co islands and the possibility of segregatio n of Cu on top of the Co film. A sandwich structure consisting of a bilayer Co film covered by 1 monolayer of Cu is found to be the lowest-energy conf iguration. We also discuss a bilayer c(2 x 2) alloy which may form due to k inetic reasons, or be stabilized at strained surface regions. Furthermore, we study the influence of magnetism on the various structures and, e.g., fi nd that Co adlayers induce a weak spin-density wave in the copper substrate .