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

我们的目标是在石墨烯中使用定义明确的磁缺陷作为自旋中心的自旋相互作用的全面理解。该系统被认为是缺陷诱导磁性的范例，这是文献[1-3]中有争议的讨论主题。虽然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在石墨烯上，但是缺少对它们之间相互作用的系统和定量研究。基于最近的一个实验，我们发现了一个明确的签名之间的优先反铁磁耦合的空缺[A1]，我们提出了一个系统的研究相结合的电子自旋共振和扫描隧道光谱，包括噪声光谱。我们将使用全局电子自旋共振测量来确定作为各种衬底上石墨烯的电子密度和空位密度的函数的耦合常数。此外，我们的目标是在本地检测有效的交换相互作用和共振信号，使用扫描探针技术。此外，我们将通过控制氧化将空位发展成锯齿形边缘，用同样的技术探测它们的自旋性质。由此产生的对石墨烯内自旋耦合特性的全面理解可能会成为其他具有无序磁性杂质的系统的蓝图。

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.