Proton irradiation effects and magnetic order in carbon structures

Proton irradiation is a reproducible method to induce magnetic order in pure carbon. In this contribution recent achievements in this field are presented. (1) Using a proton microbeam one is able to produce magnetic microstructures on pure graphite surfaces in which magnetic domain patterns at 300 K could be resolved using magnetic force microscopy (MFM). (2) Proton irradiation of polyimide films leads to clear magnetic signals at room temperature. (3) The magnetic response at the edges of carbon nanowalls has been studied using MFM, before and after proton irradiation. The results suggest the existence of strong magnetic field gradients at some of the edges indicating ferromagnetic order in part of the grown nanowalls. These studies were complemented by SQUID measurements, which show an increase of the ferromagnetic signal after irradiation.