相关论文: Ferromagnetism in Oriented Graphite Samples
This comment addresses several issues in the paper by Sepioni et al., where it is stated that the ferromagnetism in pristine highly oriented pyrolytic graphite (HOPG) reported by several groups in the previous years is most likely due to…
We report on an extensive investigation to figure out the origin of room-temperature ferromagnetism that is commonly observed by SQUID magnetometry in highly-oriented pyrolytic graphite (HOPG). Electron backscattering and X-ray…
We demonstrate direct evidence for ferromagnetic order at defect structures in highly oriented pyrolytic graphite with magnetic force microscopy at room temperature. Magnetic impurities have been excluded as the origin of the magnetic…
Ferromagnetism in carbon-based materials is appealing for both applications and fundamental science purposes because carbon is a light and bio-compatible material that contains only s and p electrons in contrast to traditional ferromagnets…
We have investigated the variation in the magnetization of highly ordered pyrolytic graphite (HOPG) after neutron irradiation, which introduces defects in the bulk sample and consequently gives rise to a large magnetic signal. We observe…
There have recently been various reports of weak ferromagnetism in graphite (1,2) and synthetic carbon materials (3) such as rhombohedral C60 (4), as well as a theoretical prediction of a ferromagnetic instability in graphene sheets (5).…
In this study, the impurity concentration and magnetic response of nine highly oriented pyrolytic graphite (HOPG) samples with different grades and from different providers were determined using ion beam microscopy and SQUID magnetometry.…
We report the observation of proximity effect in measurements performed on highly oriented pyrolitic graphite (HOPG) samples when electrical current is injected through the superconducting electrodes placed on the sample surface few…
We present a x-ray dichroism study of graphite surfaces that addresses the origin and magnitude of ferromagnetism in metal-free carbon. We find that, in addition to carbon $\pi$ states, also hydrogen-mediated electronic states exhibit a net…
We present a study of the magnetoresistance of highly oriented pyrolytic graphite (HOPG) as a function of the sample size. Our results show unequivocally that the magnetoresistance reduces with the sample size even for samples of hundreds…
We present electrical transport measurements in natural graphite and highly ordered pyrolytic graphite (HOPG), comparing macroscopic samples with exfoliated, nanofabricated specimens of nanometer thickness. The latter exhibit a very large…
Carbon materials are attracting increasing attention due to the novelty of the associated physical properties and the potential applications in high-tech devices. The possibility to achieve outstanding properties in macroscopic carbon…
We report $\beta$-detected nuclear magnetic resonance of ultra-dilute $^{8}$Li$^{+}$ implanted in highly oriented pyrolytic graphite (HOPG). The absence of motional narrowing and diffusional spin-lattice relaxation implies Li$^+$ is not…
The search for macroscopic magnetic ordering phenomena in organic materials, in particular in pure graphite, has been one of the more exciting scientific activities working in the frontiers of physics, chemistry, and materials science. In…
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 (SQUID) and magnetic…
The magnetic properties of disordered graphene and irradiated graphite are systematically studied using a combination of mean-field Hubbard model and first-principles calculations. By considering large-scale disordered models of graphene, I…
We have identified ferromagnetic- and superconducting-like magnetization hysteresis loops in highly oriented pyrolytic graphite samples below and above room temperature. We also found that both behaviors are very sensitive to…
Recently, magnetic order in highly oriented pyrolytic graphite (HOPG) induced by proton broad- and microbeam irradiation was discovered. Theoretical models propose that hydrogen could play a major role in the magnetism mechanism. We…
Far infrared magneto-transmission spectroscopy has been used to probe "relativistic" fermions in highly oriented pyrolytic and natural graphite. Nearly identical transmission spectra of those two materials are obtained, giving the signature…
We discuss recently obtained data using different experimental methods including magnetoresistance measurements that indicate the existence of metal-free high-temperature magnetic order in graphite. Intrinsic as well as extrinsic…