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

我们的目标是全面了解石墨烯中的自旋相互作用，使用定义良好的磁缺陷作为自旋中心。该系统被视为缺陷诱导磁性的范例，这是文献中有争议的讨论主题[1-3]。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已经很好地建立了，但对它们相互作用的系统和定量研究仍然缺失。基于最近的一项实验，我们发现空位之间存在明显的优先反铁磁耦合[A1]，我们提出了一种结合电子自旋共振和扫描隧道光谱（包括噪声光谱）的系统研究。我们将使用全局电子自旋共振测量来确定耦合常数作为石墨烯在各种衬底上的电子密度和空位密度的函数。此外，我们的目标是使用扫描探针技术局部检测有效的交换相互作用和共振信号。此外，我们将利用相同的技术，通过控制氧化探测其自旋特性，将空位发展成锯齿状边缘。由此产生的对石墨烯内自旋耦合特性的全面理解可能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.