Electronic and magnetic properties of carbon nanofoam produced by high-repetition-rate laser ablation

A new form of carbon material, a low-density cluster-assembled carbon nanofoam was produced by high-repetition-rate laser ablation of a glassy carbon target in an ambient non-reactive Ar atmosphere. The foam poses a unique combination of properties, such as one of the lowest solid density and high resistivity, similar to that of amorphous diamond-like films. Electron energy loss spectra demonstrate that the carbon foam has a significant, 35% in average, fraction of spa-bonding. The measured density of spins in the foam, 8.8 x 10(20) g(-1), is one of the highest observed in tetrahedrally-bonded carbon. This density of spins corresponds to paramagnetic susceptibility of about 0.01 of that for transition metals, which is in a striking contrast to diamagnetic properties of all other known allotropes of carbon. (C) 2002 Elsevier Science B.V. All rights reserved.