Chemistry Reference
In-Depth Information
CHAPTER 9
MAGNETIC STRUCTURES OF EDGE-STATE SPINS IN NANOGRAPHENE AND
A NETWORK OF NANOGRAPHENE SHEETS
Toshiaki Enoki
*
, V. L. Joseph Joly and Kazuyuki Takai
DEPARTMENT OF CHEMISTRY, TOKYO INSTITUTE OF TECHNOLOGY,
2-12-1 OOKAYAMA, MEGURO-KU, TOKYO 152-8551, JAPAN
*
TENOKI@CHEM.TITECH.AC.JP
The electronic structure of a nanographene sheet crucially depends on the shape
of its edges. In the zigzag-shaped edges, a nonbonding Π-electron state (edge
state) is created in contrast to the absence of such state in the armchair edges.
Strong spin polarization of the edge state gives rise to unconventional
magnetism in nanographene. Ultra-high vacuum STM/STS experiments
confirm the presence of the edge state in graphene edges. The magnetism of a
3 dimensional disordered network of nanographene sheets is understood on the
basis of ferrimagnetic structure of the edge-state spins in individual constituent
nanographene sheet. Electron localization in the electron transport between
nanographene sheets seriously affects the dynamical magnetic feature of the
edge-state spins. The strengthening of the inter-nanographene-sheet magnetic
interaction brings about a spin glass state.
1. INTRODUCTION
After the discovery of graphene (a single layer of graphite) in 2004,
1-4
graphene has attracted rapidly growing attention not only as a central
issue in basics science but also as a target in cutting-edge
nanotechnology. What is most interesting in graphene is the
unconventional physics behind the electronic behavior observed
experimentally. Indeed, the electronic structure of graphene is described
in terms of massless Dirac fermion, which plays in giving the
unprecedented electronic phenomena, such as anomalous quantum Hall
151
