Ferromagnetism and Structural Features of N-doped Graphene Clusters in Carbon Structures

We report that nitrogen pressure and the chemistry of the initial reagents are the efficient parameters for controlling the electron characteristics of produced carbonaceous materials, consequently affecting their magnetic properties. By manipulating these parameters, we successfully altered the sp3 /sp2 ratio within a range of 1 to 2.8 and the pyridinic-N/pyrrolic-N ratio within a range of 0.6 to 1.3. The growth of the sp3 /sp2 ratio coincided with a decrease in the fraction of pyridinic nitrogen and an increase in pyrrolic nitrogen. The magnetic properties of the materials were measured at two different temperatures (5 and 300 K) and external magnetic fields of up to 50 kOe. It was shown that increasing the sp3 /sp2 ratio led to an increase of the ferromagnetic component of the magnetic moment. This correlation was observed at both 300 K and 5 K. The explanations of the observed effects are also suggested and discussed.