Magnetic writing in carbon

Ferromagnetic microstructures, caused by localized ferromagnetic ordering, have been written in highly oriented pyrolytic graphite (HOPG) using a beam of 2.25 MeV protons, and characterized using AFM/magnetic force microscopy (MFM) and superconducting quantum interferometer device (SQUID) measurements [1,2]. Experimental evidence and theoretical predictions suggest that the ordering of carbon by protons is caused by lattice disorder created by protons coupled with the implantation of the residual protons (as hydrogen). Further work has indicated that superparamagnetic spots in polyimide foils can also be created by proton microbeam irradiation, leading the authors to conclude that the fabrication of magnetic structures of more complex shapes, and the creation of ferromagnetic nanotips by irradiating single carbon nanotubes, could lead to very useful applications of p-beam writing in the future [3].