Ferromagnetism of nanographite structures in carbon microspheres

Carbon microspheres with unusual magnetic properties have been prepared by method of solid-phase pyrolysis where metal-free
phthalocyanine was used as a precursor. The morphology, structure and magnetic properties of prepared samples were investigated
using electron microscopy, magnetometry and electron paramagnetic resonance. Carbon microspheres with a mean diameter d =
3.40±0.15 μm consist of graphitized nanocrystallites with a thickness of 5-15 graphene layers. The samples demonstrate a strong
paramagnetism with the concentration of paramagnetic centers ~ 5×1019 spin/g. In the temperature range of 5-100 K a ferromagnetism
was revealed with a maximum value of the saturation magnetization, Ms ≈ 0.03 emu/g at Т= 25К. The temperature-independent
diamagnetism with susceptibility of χDia = -1∙10-6 emu/g∙Oe was also measured.