Graphene clusters in carbon: Structural features and magnetic properties

We report that nitrogen pressure is an effective factor for controlling the electron characteristics of the produced carbonaceous materials, consequently affecting their magnetic properties. By manipulating this parameter, we successfully alter the sp3/sp2 ratio within a range of 1 to 2.7, as well as the pyridinic-N/pyrrolic-N ratio within a range of 0.6 to 1.3. It is demonstrated that an increased amount of pyrrolic nitrogen leads to a growth in the sp3/sp2 ratio. The magnetic properties of the materials were measured at two different temperatures (5 K and 300 K) and under external magnetic fields of up to 50 kOe. It is confirmed that increasing the sp3/sp2 ratio results in an increase in the saturation magnetization of N-doped carbon nanostructures. This correlation was observed at both 300 K and 5 K. Thus, we have discovered that the concentration of pyrrolic nitrogen is an effective tool for tuning the magnetic properties of carbonaceous structures. An explanation of the observed effect, including supporting DFT modeling, is also provided.