Unconventional magnetism in all-carbon nanofoam

TL;DR

This paper reports the creation of a novel all-carbon nanofoam with unique magnetic properties, characterized by a combination of sp2 and sp3 bonds, exhibiting ferromagnetic-like behavior up to 90 K due to topological defects.

Contribution

It introduces a new form of carbon nanofoam with unusual magnetic properties, produced via laser ablation, and explains the origin of magnetism as due to topological defects rather than impurities.

Findings

The nanofoam contains both sp2 and sp3 carbon bonds.

It exhibits ferromagnetic-like behavior up to 90 K.

Magnetism is attributed to topological and bonding defects.

Abstract

We report production of nanostructured carbon foam by a high-repetition-rate, high-power laser ablation of glassy carbon in Ar atmosphere. A combination of characterization techniques revealed that the system contains both sp2 and sp3 bonded carbon atoms. The material is a novel form of carbon in which graphite-like sheets fill space at very low density due to strong hyperbolic curvature, as proposed for ?schwarzite?. The foam exhibits ferromagnetic-like behaviour up to 90 K, with a narrow hysteresis curve and a high saturation magnetization. Such magnetic properties are very unusual for a carbon allotrope. Detailed analysis excludes impurities as the origin of the magnetic signal. We postulate that localized unpaired spins occur because of topological and bonding defects associated with the sheet curvature, and that these spins are stabilized due to the steric protection offered by the convoluted sheets.