Abstract We report a novel study on the magnetic properties of exfoliated HOPG lamellae exhibiting hexagonal Moire superlattices with periodicity of ~40 nm, ~26 nm, ~23 nm and ~7.7 nm corresponding to rotational angles θrot of ~0.35°, ~0.55o, ~0.62° and ~1.8o. SQUID magnetometry revealed presence of percolative ferromagnetic contributions arising from topologically disordered areas and absence of superconductive transitions. Field-dependent zero field cooled (ZFC) and field cooled (FC) measurements of the magnetization evidenced presence of magnetic irreversibilities, arising from percolative ferromagnetism. Similar magnetic features could be detected in other exfoliated lamellae and in natural graphite. Experiments involving doping of the exfoliated lamellae with sulfur, evidenced further an unusual demagnetization effect; ZFC and FC magnetic curves of doped samples revealed a partial annihilation of the ferromagnetic signals as a consequence of interactions between the sulfur species and the topologically disordered regions. Raman spectroscopy highlighted the appearance of unknown broad bands in the regions of ~500 cm−1, 1200 cm−1 and 1400 cm−1 resulting from sulfur-defect interactions.

中文翻译：

---

具有六方莫尔超晶格的硫掺杂高取向热解石墨中渗透相关信号的湮灭

摘要 我们报告了一项关于剥落的 HOPG 薄片磁性的新研究，该薄片具有六边形莫尔超晶格，周期性为~40 nm、~26 nm、~23 nm 和~7.7 nm，对应于~0.35°、~0.55o 的旋转角 θrot， ~0.62° 和 ~1.8o。SQUID 磁力测量显示存在由拓扑无序区域和超导跃迁的缺乏引起的渗透铁磁贡献。磁化强度的场相关零场冷却 (ZFC) 和场冷却 (FC) 测量证明存在由渗透铁磁性引起的磁不可逆性。在其他剥落薄片和天然石墨中可以检测到类似的磁性特征。涉及用硫掺杂剥落的薄片的实验进一步证明了不寻常的退磁效果；掺杂样品的 ZFC 和 FC 磁曲线显示，由于硫物质与拓扑无序区域之间的相互作用，铁磁信号部分消失。拉曼光谱突出显示了约 500 cm-1、1200 cm-1 和 1400 cm-1 区域因硫缺陷相互作用而出现的未知宽带。