title: Room-temperature magnetic order on zigzag edges of narrow graphene nanoribbons.
abstract: The possibility that non-magnetic materials such as carbon could exhibit a novel type of s-p electron magnetism has attracted much attention over the years, not least because such magnetic order is predicted to be stable at high temperatures. It has been demonstrated that atomic-scale structural defects of graphene can host unpaired spins, but it remains unclear under what conditions long-range magnetic order can emerge from such defect-bound magnetic moments. Here we propose that, in contrast to random defect distributions, atomic-scale engineering of graphene edges with specific crystallographic orientation--comprising edge atoms from only one sub-lattice of the bipartite graphene lattice--can give rise to a robust magnetic order. We use a nanofabrication technique based on scanning tunnelling microscopy to define graphene nanoribbons with nanometre precision and well-defined crystallographic edge orientations. Although so-called 'armchair' ribbons display quantum confinement gaps, ribbons with the 'zigzag' edge structure that are narrower than 7 nanometres exhibit an electronic bandgap of about 0.2-0.3 electronvolts, which can be identified as a signature of interaction-induced spin ordering along their edges. Moreover, upon increasing the ribbon width, a semiconductor-to-metal transition is revealed, indicating the switching of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferromagnetic configuration. We found that the magnetic order on graphene edges of controlled zigzag orientation can be stable even at room temperature, raising hopes of graphene-based spintronic devices operating under ambient conditions.
authors.affiliation: Research Centre for Natural Sciences, Institute of Technical Physics and Materials Science, Nanotechnology Department, 2D Nanoelectronics "Lendület" Research Group, Budapest 1121, Hungary.
authors.forename: Gábor Zsolt
authors.initials: GZ
authors.lastname: Magda
authors.affiliation: Korea Research Institute of Standards and Science, Center for Nanometrology, Daejeon 305-340, South Korea.
authors.forename: Xiaozhan
authors.initials: X
authors.lastname: Jin
authors.affiliation: 1] Wigner Research Centre for Physics, Institute of Solid State Physics and Optics, Strongly Correlated Systems "Lendület" Research Group, Budapest 1121, Hungary [2] Department of Theoretical Physics, University of Szeged, Szeged 6720, Hungary.
authors.forename: Imre
authors.initials: I
authors.lastname: Hagymási
authors.affiliation: Research Centre for Natural Sciences, Institute of Technical Physics and Materials Science, Nanotechnology Department, 2D Nanoelectronics "Lendület" Research Group, Budapest 1121, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Vancsó
authors.affiliation: Research Centre for Natural Sciences, Institute of Technical Physics and Materials Science, Nanotechnology Department, 2D Nanoelectronics "Lendület" Research Group, Budapest 1121, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Osváth
authors.affiliation: Research Centre for Natural Sciences, Institute of Technical Physics and Materials Science, Nanotechnology Department, 2D Nanoelectronics "Lendület" Research Group, Budapest 1121, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Nemes-Incze
authors.affiliation: Korea Research Institute of Standards and Science, Center for Nanometrology, Daejeon 305-340, South Korea.
authors.forename: Chanyong
authors.initials: C
authors.lastname: Hwang
authors.affiliation: Research Centre for Natural Sciences, Institute of Technical Physics and Materials Science, Nanotechnology Department, 2D Nanoelectronics "Lendület" Research Group, Budapest 1121, Hungary.
authors.forename: László P
authors.initials: LP
authors.lastname: Biró
authors.affiliation: Research Centre for Natural Sciences, Institute of Technical Physics and Materials Science, Nanotechnology Department, 2D Nanoelectronics "Lendület" Research Group, Budapest 1121, Hungary.
authors.forename: Levente
authors.initials: L
authors.lastname: Tapasztó