Regensburg 2004 – wissenschaftliches Programm

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MA: Magnetismus

MA 11: Magnetische Materialien

MA 11.1: Vortrag

Dienstag, 9. März 2004, 10:15–10:30, H22

Magnetic Carbon: An explicit evidence on ferromagnetism induced by proton irradiation — •Pablo Esquinazi, Daniel Spemann, Roland Höhne, Annette Setzer, Kyoo-hyun Han, and Tilman Butz — Institut für Experimentelle Physik II, Universität Leipzig, Linnestrasse 5, D-04103 Leipzig

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 several reports claiming an unusually large magnetization in pyrolytic carbon and oxidized 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 ferromagnetic impurities. In this contribution we present SQUID and MFM results on ferro- or ferrimagnetism induced by proton irradiation on pure pyrolytic graphite. The impurity concentration (< 0.3 µg Fe in 1g C) was measured by RBS and PIXE at each irradiation stage. The overall results including those obtained from presure- and photo-polymerised fullerenes indicate that room-temperature ferromagnetism in metal-free carbon structures containing only s- and p-electrons is a reality.