石墨烯纳米带中的铁磁性：分裂与氧化解链带
Ferromagnetism in graphene nanoribbons: split versus oxidative unzipped ribbons
摘要：
采用静态磁化强度和电子自旋共振测量相结合的方法研究了两种类型的石墨烯纳米带：（a）钾分裂石墨烯纳米带（GNRs）和（b）氧化解链和化学转化的石墨烯纳米带（CCGNRs）的磁性。这两种类型的薄带具有明显不同的磁性。虽然在这两种类型的带中观察到低温铁磁体样特征，但这种室温特征仅在钾分裂带中存在。GNRs表现出负的交换偏差，但CCGNRs表现出“正的交换偏差”。电子自旋共振测量推断，碳相关的缺陷可能负责在这两种类型的带中观察到的磁行为。此外，质子超精细耦合强度已获得的超精细子能级关联实验上的GNRs。电子自旋共振没有提供钾（簇）相关信号的存在下，强调了固有的磁性本质的丝带的迹象。我们的综合实验结果可能推断铁磁团簇与反铁磁区共存导致无序磁相。我们讨论了这两种类型的带状物的磁性行为中所观察到的对比的起源。
英文摘要：
Two types of graphene nanoribbons: (a) potassium-split graphene nanoribbons (GNRs), and (b) oxidative unzipped and chemically converted graphene nanoribbons (CCGNRs) were investigated for their magnetic properties using the combination of static magnetization and electron spin resonance measurements. The two types of ribbons possess remarkably different magnetic properties. While the low temperature ferromagnet-like feature is observed in both types of ribbons, such room temperature feature persists only in potassium-split ribbons. The GNRs show negative exchange bias, but the CCGNRs exhibit a 'positive exchange bias'. Electron spin resonance measurements infer that the carbon related defects may responsible for the observed magnetic behaviour in both types of ribbons. Furthermore, proton hyperfine coupling strength has been obtained from hyperfine sublevel correlation experiments performed on the GNRs. Electron spin resonance provides no indications for the presence of potassium (cluster) related signals, emphasizing the intrinsic magnetic nature of the ribbons. Our combined experimental results may infer the coexistence of ferromagnetic clusters with anti-ferromagnetic regions leading to disordered magnetic phase. We discuss the origin of the observed contrast in the magnetic behaviours of these two types of ribbons.
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