Effect of edges on the stability and magnetic interaction of Co atoms embedded in zigzag graphene nanoribbons

Abstract

We report the results of first-principles calculations for the atomic, electronic, and magnetic properties of the Co atoms embedded in divacancy defects in graphene nanoribbons with zigzag-shaped edges. We find that the edges play an important role in the stabilization of a Co-divacancy complex near the edge, where the edge C atoms undergo large relaxations, resulting in a tilted-edge structure. When Co is positioned in the middle of the ribbon, the edge C atoms generally remain on the sheet, forming a flat-edge structure due to the small edge effect. The spin polarization of the edges is determined by two bipartite lattices separated by the Co atom. When a Co-divacancy pair is formed near the same edge, the edge structure is significantly modified. The magnetic interaction between the Co atoms is either ferromagnetic or antiferromagnetic, depending on the relative positions of the Co atoms, and its magnetic ordering can be described by the combined effect of the bipartite lattices formed around individual Co atoms. DOI: 10.1103/PhysRevB.87.085435