Self-assembled magnetic dots, antidots, dot chains, and stripes: Epitaxial Co on Ru(0001)

Lateral magnetic nanostructures have been grown via molecular beam epitaxy in ultrahigh vacuum and characterized ex-situ with atomic force and magnetic force microscopy. We observed that epitaxial growth of Co onto Ru(0001) at elevated temperature results in three-dimensional Co islands (dots) or a flat Co film network with deep holes (antidots) in truncated pyramidal shapes. The lateral size of these dots/antidots, in the order of 100 nm, tends to be uniform at each given coverage. We attribute the growth mode mainly to strain relaxation of Co epitaxy on Ru, which has a 8% lattice mismatch. In addition, we have explored the placement of these dots on a grooved Ru(0001) surface. The dots automatically align into linear chains along the asymmetric grooves to form either dot chains or continuous stripes, which would open new opportunities in creating either ordered magnetic arrays or arbitrary arrangements.