Irreversible magnetic properties of carbon nanoparticles
Department of Mathematics and Physics, Lappeenranta
University of Technology, PO Box 20, FIN-53851
2 institute of Applied Physics, Academy of Sciences of Moldova, Academiei Str. 5, MD-2028 Kishinev, Moldova
3 South Ural State University, 454080 Chelyabinsk, Russia
4 A.F. loffe Physico-Technical Institute, 194021 St. Petersburg, Russia
Magnetic properties of powder and glassy samples with carbon nanoparticles. not intentionally doped and doped with Ag, Au and Co, are investigated at temperatures T ~ 3 — 300 K in magnetic fields B up to 5 T. Magnetization M (T) exhibits in low fields of B = 1 — 50 mT a strong irreversibility, which is suppressed above B ~ 1 T. The high-temperature (T ~ 200 — 300 K) dependence of M on B demonstrates a saturation above B ~ 2 T. Magnetic hysteresis is observed already at 300 K. exhibiting a power-law temperature decay of the coercive field. Analysis of the experimental data suggests a concentration of the magnetization close to the surface of the carbon nanoparticles. This is consistent with the origin of magnetism in nanocarbon due to intrinsic surface defects. Deviations of macroscopic and microscopic parameters in the Co-doped sample from those in the other samples imply an influence of the Co ions and/or clusters.
© Owned by the authors, published by EDP Sciences, 2013