Magnetic carbon: Explicit evidence of ferromagnetism induced by proton irradiation

The recently found ferromagnetic signals in pure graphite and in polymerised fullerenes are received mainly with scepticism by most of the scientific community. Actually, before those results were published, there were already several reports claiming an unusually large magnetization in pyrolytic carbon and oxidised fullerenes, without attracting the attention of the community. This scepticism may be well founded since not always a careful and systematic impurity study was provided to quantify the influence of ferromagnetic impurities. In this article and after a brief review of the existing data on magnetic carbon, we present and discuss recently obtained results on the ferromagnetism (or ferrimagnetism) induced by proton irradiation on pure pyrolytic graphite, which strengthen the importance of hydrogen in the formation of the magnetic ordering. The overall results indicate that room-temperature ferromagnetism in carbon-based structures containing only p- and s-electrons is a reality.