Magnetotransport of nanoporous nanographite domain network and its oxygen-adsorption effect

• Published in: The Journal of physics and chemistry of solids 2008-05, Vol.69 (5), p.1155-1157
• Main Authors: Sugihara, Ko, Takahara, Katsunori, Takai, Kazuyuki, Enoki, Toshiaki
• Format: Article
• Language: English
• Subjects: A. Magnetic materials; A. Microporous materials; A. Nanostructures; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; D. Electronic structure; D. Magnetic properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in multilayers, nanoscale materials and structures; Exact sciences and technology; Materials science; Nanoscale materials and structures: fabrication and characterization; Physics
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2007.10.080

Nanographite has localized spins originating from nonbonding π-electron state (edge state) on their edge sites. Nanoporous activated carbon fibers (ACFs), which consist of a 3D disordered network of nanographite metallic domains, show a large positive magnetoresistance at low temperatures. The magnetoresistance is greatly reduced upon magnetic oxygen adsorption. The large oxygen-adsorption effect on the magnetotransport is theoretically explained in terms of the interaction between the electric dipole moment of the edge-state π-electron and the electric quadrupole moment of an adsorbed oxygen molecule. The theoretical calculation reproduces the experimentally reported strength of the exchange interaction between oxygen molecule spin and the edge-state spin, in addition to the behavior of the magnetoresistance.