Chemistry Reference
In-Depth Information
(
J
1
~ (10
-1
- 10
-2
)
J
0
), works to couple the ferromagnetically-arranged
edge-state spin clusters between the zigzag edge regions embedded in the
circumference. The strength and sign (ferromagnetic/antiferromagentic)
of
J
1
vary depending on the mutual geometrical relation between the
zigzag edges concerned. The cooperation of
J
0
and
J
1
therefore creates
ferrimagnetic spin structure with a non-zero net magnetic moment in
an individual nanographene sheet as shown in Fig. 4(b).
25,26
In the
network of nanographite domains, there are two kinds of additional
exchange interactions; inter-nanographene-sheet interaction (
J
2
) and
inter-nanographite-domain interaction (
J
3
), which are both weakly
antiferromagnetic (
J
0
>
J
1
>>
J
2
>
J
3
).
24-26
Eventually, the magnetism of
ACFs is given as a consequence of the cooperation of
J
0
,
J
1
,
J
2
and
J
3
.
LOCALIZED SPIN
OF EDGE STATE
NANOPORE
(A)
(B)
3~4
GRAPHENE
SHEETS
NANOGRAPHITE
L
A
~ 3 NM
Fig. 4. (a) The schematic structural model of activated carbon fiber (ACF). (b) An
individual nanographene sheet in a nanographite domain of ACF, and the spatial
distribution of edge-state spins.
J
0
and
J
1
are intra- and inter-zigzag-edge interactions,
respectively.
3.1.
Effect of electron localization on the magnetism of the
edge-state spins
Before discussing the magnetism of ACFs, let us see the electron
transport properties of ACFs. The non-treated ACF shows insulating
behavior in their electron transport properties as shown in Figs. 5(a) and
(b) with the temperature dependence of the conductivity/resistivity. The
resistivity obeys the formula of the Coulomb-gap type variable range
hopping in a fractal geometry network in Anderson insulator;
24,27-29
