Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Defect induced magnetism in carbon based materials has many attractive perspectives in the fundamental understanding of magnetism as well as in future spintronic applications. Graphite has been reported that it can be ferromagnetic after proton irradiation. After that, successive investigation was done for confirming the ferromagnetism in graphite and for finding other carbon based materials to be ferromagnetic. So far although the mechanism of ferromagnetism in carbon-based materials is still an open question, more and more experiments show some common features: First, paramagnetism can be largely enhanced by introducing defects. Second, ferromagnetism only appears under certain defect concentration. Third, defects induced or disturbed electron states play an important role to generate local moments and to establishing the ferromagnetic coupling. In the past most of researchers used ions implantation to introduce defects in graphite or graphene. This technology usually generates defect in the near--surface and it is hard to effectively increasing the total number of defect in the whole matrix. Consequently, the magnetic signal is so weak that confuses the interpretation for the source of the observed ferromagmetism. To obtain more reliable information, thereby to better understand this phenomenon, it is necessary to enhance the total number of defect states and simultaneously keep defect concentration constant when the ferromagnetism appears. So in this contribution we use neutron irradiation to extend defect region in graphite from the near surface region to the whole sample. We present the magnetic properties and X-ray absorption spectroscopy of irradiated graphite.