Electronic and magnetic effects of a stacking fault in cobalt nanoscale islands on the Ag(111) surface

Abstract

By utilizing spin-polarized scanning tunneling microscopy (STM) and spectroscopy, we observe the coexistence of perpendicularly and in-plane magnetized cobalt nanoscale islands on an Ag(111) surface. The magnetization direction has the relationship with the observed moir\'e-corrugation amplitude on the islands; the islands with stronger moir\'e corrugation show perpendicular magnetization, and the ones with weaker moir\'e corrugation exhibit in-plane magnetization. We calculate the magnetic anisotropy energy for various stackings of a Co nanostructure based on density functional theory, and we reveal that perpendicular magnetic anisotropy is reduced drastically with increasing fcc stacking faults in the Co layer. Simulated STM images reproduce the moir\'e-corrugation difference observed experimentally when the stacking difference between perpendicularly and in-plane magnetized islands is considered. These theoretical analyses strongly suggest that the electronic and magnetic differences between the two types of islands are caused by the presence of fcc stacking faults in the intrinsic hcp stacking of Co.