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Magnet Made Of Pure Carbon

October 24, 2001

All known magnets contain metals and so far scientists believed that non-metallic material could not behave like a strong magnet. However, at the end of 20th century, some organic substances with strong magnetic properties were found, but they were magnetic only at very low temperatures, just above liquid helium.

It seemed impossible to obtain ferromagnetic material consisted of carbon only, but physicists from the Institute of High Pressure Physics of Russian Academy of Sciences in Troitsk, Moscow Region, have done it. The material made of pure carbon has retained strong magnetic properties up to 230C.

As it often happens, the discovery of the carbon magnet was made by chance. "We studied transformations of fullerene C60 at high pressures and temperatures and synthesised a series of materials which surprisingly happened to be magnets", said Valery Davydov, head of the Troitsk research group.

The new material consisted of rhombohedral polymerized phase of fullerene C60. It has graphite-like lamellar structure; the difference is that in graphite the layers are formed by C atoms, whereas in the new material they are formed by C60 molecules. To make carbon magnetic, it takes to put it under pressure of 60 000 atmospheres and heat up to 700-800? C. Electrophysic characteristics of the new materials were examined by Tatiana Macarova, a physicist from Ioffe Physico-Technical Institute, St Petersburg, who is currently working in Umea University in Sweden. At first, the scientists tried to explain the discovered magnetic properties by effects of metallic impurities. In collaboration with researchers from Sweden, Germany and Brazil, they studied new series of samples in detail and proved that the content of metallic impurities was extremely low, so it could not result in the observed magnetism. That means that carbon material itself acquires strong magnetic properties during the high-pressure thermal processing.

The scientists have no clear explanation for the discovered effect of carbon magnetising. One of possible mechanisms involves spins of unpaired electrons, which could be oriented in one direction and impart magnetic properties to the carbon material. The results have been published in Nature 18 October 2001 (vol 413, p 716).

Informnauka (Informscience) Agency