Room-temperature magnetic order on zigzag edges of narrow graphene nanoribbons
Room-temperature magnetic order on zigzag edges of narrow graphene nanoribbons
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DOI：
10.1038/nature13831
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发表时间：
2014-10-30
期刊：
影响因子：
64.8
通讯作者：
Tapaszto, Levente
中科院分区：
文献类型：
--
作者：
Magda, Gabor Zsolt;Jin, Xiaozhan;Tapaszto, Levente
多年来，非磁性材料如碳可能表现出一种新型的S p电子磁性的可能性引起了人们的极大关注，尤其是因为这种磁序被预测在高温下是稳定的[1]。已经证明，石墨烯的原子级结构缺陷可以存在未配对的自旋(2，3)，但目前尚不清楚在什么条件下可以从这种缺陷束缚的磁矩中产生长程磁序。在这里，我们提出，与随机缺陷分布相反，具有特定晶体取向的石墨烯边缘的原子尺度工程-仅包括来自二元石墨烯晶格的一个子晶格的边缘原子-可以产生稳健的磁序。我们使用基于扫描隧道显微镜的纳米制造技术(4)来定义具有纳米精度和明确的晶体边缘取向的石墨烯纳米带。尽管所谓的扶手椅带显示出量子限制带，但具有小于7纳米的锯齿形边缘结构的带显示出约0.2-0.3电子伏特的电子带隙，这可以被识别为沿其边缘的相互作用诱导的自旋有序的特征。此外，随着带宽的增加，出现了半导体到金属的转变，表明相反带边之间的磁耦合从反铁磁构型转变为铁磁构型。我们发现，即使在室温下，可控之字形取向的石墨烯边缘上的磁序也可以稳定，这为基于石墨烯的自旋电子器件在常温下工作带来了希望。
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(1). It has been demonstrated that atomic-scale structural defects of graphene can host unpaired spins(2,3), 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(4) 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.