Magnetic Graphite

Physicists at the University of Leipzig have irradiated graphite with protons to produce a lightweight, pure-carbon, metal-free, room temperature magnet. Pure carbon comes in several notable solid forms - graphite (powdery because with its two dimensional planes of atoms are so loosely bound--hence the use of graphite as a lubricant or pencil lead), diamond (hard because its constituents are well connected to atoms in all 3 dimensions), buckyballs (60-atom soccerballs), and nanotubes. All have important electrical properties, but in general they are not magnetic. Until now no pure-carbon sample was known to be magnetic, except when doped and held at temperatures close to absolute zero. In the Leipzig experiment, the protons were supplied by a nearby accelerator, and their presence in the sample in small amounts was just enough to inspire a small magnetic ordering among the carbon atoms. The magnetism was then measured by sensitive SQUID detectors and magnetic force microscopy at the surface. According to one of the researchers, Pablo Esquinazi (+49-341-9732751), room-temperature magnetic graphite might have interesting applications in spintronics (some theoretical work suggests that atoms in a 2-dimensional graphite layer sprinkled with protons might be 100% spin polarizable) or as a data storage medium in which magnetic bits could be inscribed in a pure carbon film rather than in metal or metal-semiconductor films. Weak magnetism in graphite might also have implications for the study of biomolecules, which are rich in carbon-hydrogen bonds, or for astronomy since space is rich in carbon-filled gas clouds undergoing irradiation. (Esquinazi et al., Physical Review Letters, 28 November)