Magnetic Properties Of Graphene Nanodisk And Nanocone Powders At Low Temperatures

Our aim is the study of magnetization phenomena of carbon powders consisting of graphene nanocones and nanodisks. Magnetization measurements were carried out using a superconducting quantum interference device in magnetic fields -5 < B < 5 T for temperatures in the range 0.5 <= T < 300 K. We have observed that magnetization M depends on temperature T as a power law M proportional to T-alpha where the scaling exponent alpha = 0.79 +/- 0.04 was determined. We found that the magnetization consists of a diamagnetic background and a paramagnetic contribution of localized spins. Considering saturation magnetization M-S in the free spin magnetization model and diamagnetic susceptibility chi(D) for independent of temperature T we found that the effective spin value S increases from S = 1/2 at temperature T > 20 K to S = 3 at low temperatures 0.5 <= T <= 20 K.