Unconventional magnetism in all-carbon nanofoam

Abstract

We report production of nanostructured magnetic carbon foam by a high-repetition-rate, high-power laser ablation of glassy carbon in Ar atmosphere. A combination of characterization techniques revealed that the system contains both sp 2 and sp 3 bonded carbon atoms. The material is a form of carbon containing graphitelike sheets with hyperbolic curvature, as proposed for "schwarzite." The foam exhibits ferromagnetic-like behavior up to 90 K, with a narrow hysteresis curve and a high saturation magnetization. Such magnetic properties are very unusual for a carbon allotrope. Detailed analysis excludes impurities as the origin of the magnetic signal. We postulate that localized unpaired spins occur because of topological and bonding defects associated with the sheet curvature, and that these spins are stabilized due to the steric protection offered by the convoluted sheets.

Highly conductive nanoclustered carbon:nickel films grown by pulsed laser deposition

“…Ferrari et al [24] suggest that annealing at temperatures below ? 873-973 K produces only a small number of new sp 2 sites, inside an sp 3 phase, but that these additional sites may cause an exponential increase in conductivity due to the (slight) increase in hopping centres. Since clusterassembled carbon films contain similar structures [6], it is likely that a similar mechanism leads to the enhanced conductivity observed here upon annealing of the undoped films.…”

“…While the usefulness of carbon in many of these applications critically depends on its ability to form both sp 2 and sp 3 bonds, the morphology of the material also has an important effect on its overall properties [3].…”

Ion and electron irradiation-induced effects in nanostructured materials

“…Observations of ferromagnetism in various metal-free carbon systems, such as polymerized fullerenes and graphite, 285,[457][458][459][460] have stimulated much experimental and theoretical research work on the magnetic properties of allcarbon systems, for an overview, see Ref. 461 and references therein.…”

Influence of Negative Field Cooling on the Exchange Bias Properties of Potassium Split Graphene Nanoribbons

“…The possibility of the cluster magnetism in the graphene-derived materials has been observed earlier in literature by various groups [25][26][27]. Furthermore, there exists a loop opening at the origin which indicates ferromagnetic behavior.…”