Magnetic properties of carbon nanoparticles

Magnetization M (T, B) of powder and glassy samples containing carbon nanoparticles is investigated in the interval of temperatures T between ∼ 3 - 300 K and magnetic fields B up to 5 T. Low-field magnetization, M (T), exhibits a strong magnetic irreversibility, which is suppressed above the field of ∼ 1 T. The dependence of M (B) saturates at high temperatures above B ∼ 2 T, magnetic hysteresis is observed already at 300 K. The values of the saturation magnetization, the coercivity field and the maximum blocking temperature are obtained. Analysis of the experimental data gives evidence for concentration of the magnetization close to the surface of the particles, which is consistent with the origin of magnetism in nanocarbon presumably due to intrinsic disorder and surface defects.