At the American Physical Society in Montreal, March 22-26, physicists John Giapintzakis of the University of Crete/IESL-FORTH, Andrei Rode of the Australian National University, and colleague David Tománek of Michigan State University announced an intriguing new property of carbon nanofoams. They have discovered that carbon nanofoams are attracted by a magnet - they are ferromagnetic.

Andrei Rode		David Tománek

Incredibly lightweight carbon nanofoams, essentially a fifth major allotrope of carbon, were discovered several years ago. Now, a collaboration between researchers in Greece, Australia, and Russia has led to a new technique for converting disordered solid carbon into a gossamer web of carbon-atom clusters using a high-power laser. The resulting clusters have an average diameter of between six and nine nanometers and are randomly interconnected. This frothy material is not only ferromagnetic, it is a semiconductor. Such properties taken together hint at device applications in spintronics; an emerging field that exploits the intrinsic spin of electrons as well as their charge in electronics devices.

	Carbon foams could be used in spintronics devices that consign conventional electronics to the scrapheap (Credit: David Bradley)

The researchers concede that the ferromagnetic behaviour of their material fades within a few hours at room temperature, although it can be conserved for much longer at lower temperatures. They also point out that small amounts of nickel and iron impurities have been found in their nanofoams, but calculated that this could account for only 20% of the strength of the material's ferromagnetic field. They suggest that the magnetic behavior is due to the complex microstructure of the foam in which they observe heptagonal structures having an unpaired electron.

Carbon nanofoams might have applications outside spintronics. As an injectable material they could be used as a non-toxic aid for magnetic resonance imaging in medicine. They could also be used as a novel therapy for destroying tumors. Injected directly into the tumor, the foam could absorb infra-red energy and lead to lethal overheating of the cancerous tissue without damaging surrounding healthy cells.