Formation of Spin‐Collinear Domain Walls at Graphene Nanoflake Edges

The size dependence of the magnetic edge states in zigzag graphene nanoflakes (GNFs) with different aspect ratios is studied using density functional theory. The results show that GNFs smaller than a certain critical size exhibit a closed‐shell nonmagnetic ground state, whereas at the critical size or larger, the nanoflakes have an open‐shell antiferromagnetic (AFM) ground state with a spin density localized along the edges. The formation of a spin‐collinear domain wall beyond the critical size, where the AFM order emerges, was analyzed, finding that this transition is a result of multiple symmetry breakings of highest singly occupied molecular orbitals (SOMO and SOMO‐1). The collinear domain wall is strongly dependent on the perpendicular distance between parallel edges. Furthermore, it is found that the formation of the collinear domain wall in zigzag GNFs is associated with the behavior of the bond‐length alternation at the edges. The emergence of magnetism in zigzag graphene nanoflakes (GNFs) with different aspect ratios is studied using density functional theory. GNFs above a critical size have an antiferromagnetic ground state with a spin‐collinear domain wall (SCDW) along the edges. The SCDW is characterized by a longitudinal spin wave with a node in the middle of the nanostructure edge.