Transport properties of a few hundreds of nanometers thick (in the graphene plane direction) lamellae of highly oriented pyrolytic graphite (HOPG) have been investigated. Current-voltage characteristics as well as the temperature dependence of the voltage at different fixed input currents provide evidence for Josephson-coupled superconducting regions embedded in the internal two-dimensional interfaces of HOPG, reaching zero resistance at low enough temperatures. 13 References 13

Granular superconductivity in powders of small graphite grains (several tens of micrometers) is demonstrated after treatment with pure water. The temperature, magnetic field and time dependence of the magnetic moment of the treated graphite powder provides evidence for the existence of superconducting vortices with some similarities to high-temperature granular superconducting oxides but even at temperatures above 300 K. Room temperature superconductivity in doped graphite or at its interfaces appears to be possible.

We have studied the transport properties of TEM lamellae obtained from a pyrolytic graphite sample with electrical contacts at the edges of the embedded interfaces. The temperature dependence of the resistance as well as the current-voltage characteristic curves are compatible with the existence of Josephson coupled superconducting regions. The transition temperature at which the Josephson behavior sets in, decreases with the interface width and vanishes for width below 200 nm. This unexpected behavior is apparently due to the influence of weak localization effects on the superconducting critical temperature.

We have studied the transport properties of transmission electron microscope (TEM) lamellae obtained from a pyrolytic graphite sample of grade B (SPI-II) with electrical contacts at the edges of the graphene layers. The temperature, magnetic field, input current dependence of the resistance as well as the current-voltage characteristic curves are compatible with the existence of granular superconductivity below 5 K. TEM pictures of the studied lamellae reveal clear differences of the embedded interfaces to those existing in more ordered pyrolytic samples, which appear to be the origin for the relatively lower temperatures at which the granular superconductivity is observed.

We have studied the changes in the ferromagnetic behavior of graphite powder and graphite flakes after treatment with diluted sulphuric acid. We show that this kind of acid treatment enhances substantially the ferromagnetic magnetization of virgin graphite micrometer size powder as well as in graphite flakes. The anisotropic magnetoresistance (AMR) amplitude at 300 K measured in a micrometer size thin graphite flake after acid treatment reaches values comparable to polycrystalline cobalt. PACS numbers: 81.05.uf,75.50.Dd The possibility to trigger magnetic order in metalfree graphite by lattice defects or non-magnetic adatoms like hydrogen attracts the interest of basic and applied research fields 1 . Recently published element specific x-ray magnetic circular dichroism (XMCD) measurements at the carbon K-edge in graphite samples 2,3 clearly demonstrated that the reported magnetic order in metal-free graphite 4? is not related to magnetic impurities. Published results from different groups indicate that vacancies 5-7 and/or hydrogen 3,8 can trigger this phenomenon, making the graphite structure the archetype of defect induced magnetism (DIM), a phenomenon that is being now found in nominally non-magnetic oxides 9,10 as well as in Si-based samples 11 for example. In case of graphite magnetic order has been also achieved by a pulsed arc ignited between two graphite electrodes in ethanol 12 . In general, however, the obtained yield remains small, partially because of the necessary delicate balance between a defect density of the order ∼ 5%, their positions and the lattice structure. For applications it is necessary therefore to find simpler methods to transform graphite in a magnet with reasonable high magnetization.XMCD results in untreated as well as in proton irradiated bulk pyrolytic graphite provide clear hints for the influence of hydrogen atoms, especially a spin polarization splitting near the Fermi level 3 in qualitative agreement with theoretical work published previously 8 . The aim of the here reported study was to find a simpler method to trigger magnetic order in graphite samples of mesoscopic size by including hydrogen at least in the near surface region without destroying its lattice structure or including further defects or contaminants. One possibility is to treat carbon with sulfuric acid leading to a hydrogen doping in the graphite structure.Two kinds of graphite samples have been used in this work, namely an ultrapure graphite powder (impurity content < 1 ppm) consisting of platelet-like grains of average size 10 × 10 × 3µm 3 (see inset in Fig. 1) and a micrometer size graphite flake of thickness ≃ 45 nm (see inset in Fig. 3). The influence of the sulphuric acid on the powder has been measured using a superconducting quantum interferometer device (SQUID) and by trans-port measurements in the case of the graphite flake, especially the anisotropic magnetoresistance (AMR) at different angles between field and current for fields applied parallel to the graphene planes of the sample.