K.-H. Han

Induced Magnetic Ordering by Proton Irradiation in Graphite

We provide evidence that proton irradiation of energy 2.25 MeV on highly oriented pyrolytic graphite samples triggers ferro- or ferrimagnetism. Measurements performed with a superconducting quantum interferometer device and magnetic force microscopy reveal that the magnetic ordering is stable at room temperature.

Magnetism in photopolymerized fullerenes

Abstract The phototransformation of bulk C60 and laser- and electron-beam treatment of C60 films in air changes their magnetic properties. Nonlinear magnetization is observed only for samples irradiated in the presence of oxygen, while, in the case of pressure-polymerized C60, oxygen adversely affects the magnetic properties. The contrasting roles of oxygen in these processes are discussed. Magnetic force microscopy shows that laser- and electron-beam irradiation of fullerene films produces magnetic images which are highly correlated with the topographic images.

Observation of intrinsic magnetic domains in C60 polymer

A C60 polymer has been characterized for the first time with respect to impurity content and ferromagnetic properties by laterally resolved particle induced X-ray emission (PIXE), superconducting quantum interference device (SQUID) and magnetic force microscopy (MFM) in order to detect intrinsic ferromagnetic domains. In parts of the pure regions (concentration of magnetic impurities <1 μg/g), we found stripe-domain magnetic images with different orientations of domain magnetization. The size of the regions where magnetic domains were observed is ∼30% of the pure region. All these results reveal that the polymerized C60 sample is a mixture of magnetic and non-magnetic parts and only a fraction of the sample contributes to the ferromagnetism.

Magnetic properties of carbon phases synthesized using high-pressure high-temperature treatment

Magnetic properties of carbon phases synthesized using high-pressure high-temperature treatment.