Magnetism of vacancies and edge states in graphene probed by electron spin resonance and scanning tunneling spectroscopy

我们的目标是使用定义明确的磁性缺陷作为自旋中心，全面了解石墨烯中的自旋相互作用。该系统被认为是缺陷感生磁学的一个范例，这在文献[1-3]中是一个有争议的主题。虽然石墨烯的狄拉克点共振和单个空位的顺磁性在实验上得到了很好的证实，但缺乏对它们相互作用的系统和定量的研究。基于最近的一次实验，我们发现了空位间明显的反铁磁择优耦合[A1]，我们建议结合电子自旋共振和包括噪声光谱在内的扫描隧道光谱进行系统的研究。我们将使用全局电子自旋共振测量来确定作为石墨烯在不同衬底上的电子密度和空位密度的函数的耦合常数。此外，我们的目标是使用扫描探针技术对有效的交换相互作用和共振信号进行局部检测。此外，我们还将通过控制氧化，用同样的技术探测空位的自旋性质，从而将空位发展成锯齿形的边缘。由此产生的对石墨烯中自旋耦合性质的全面了解可能会为其他具有无序磁性杂质的系统提供蓝图。

We aim at a comprehensive understanding of spin interactions in graphene using well-defined magnetic defects as spin centers. The system is regarded as a paradigm for defect induced mag-netism, which is a controversially discussed subject in the literature [1-3]. While the Dirac point resonance and the paramagnetism of individual vacancies are experimentally well established for graphene, a systematic and quantitative study of their mutual interactions is missing. Based on a recent experiment where we have found a clear signature of preferential antiferromagnetic coupling between the vacancies [A1], we propose a systematic study by a combination of electron spin resonance and scanning tunneling spectroscopy including noise spectroscopy. We will determine the coupling constants as a function of electron density and vacancy density of graphene on various substrates using global electron spin resonance measurements. Moreover, we aim at a local detection of effective exchange interactions and resonance signals using scanning probe techniques. We will, moreover, develop the vacancies into zig-zag edges by controlled oxidation probing their spin properties by the same techniques. The resulting comprehensive understanding of spin coupling properties within graphene might serve as a blueprint for other systems with disordered magnetic impurities.