Chemistry Reference
In-Depth Information
(a)
10
Μ
W
1
Μ
W
6
6
4
4
2
0
10
20
30
6
(b)
5
2.8
4
2.6
2.4
3
2.2
0
10
20
30
2
0.2
(c)
0.1
0.0
0
50
100
150
200
250
300
T (K)
Fig. 6. The temperature dependence of the ESR intensity, ESR line width, and the
reciprocal of the static susceptibility of the non-heat-treated ACFs. The ESR signals are
observed with microwave powers of 1 and 10 ΜW (From reference 26).
intensity, ESR line width ∆
H
PP
and static magnetic susceptibility of the
edge-state spins in the non-heat-treated ACFs.
26
The intensity at 1 ΜW
obeys the Curie law down to 30 K, and suddenly drops by 50 % below
20 K. ∆
H
PP
follows a trend corresponding to the behavior of the
intensity. ∆
H
PP
decreases linearly from 6.2 to 2.2 mT upon lowering of
the temperature down to 30 K, and suddenly increases by 30 % (0.6 mT)
below 20 K. In the elevated microwave power (10 ΜW) the sudden
change in the signal properties becomes a smooth variation as shown in
Figs. 6(a) and (b). Such sensitive nature of the ESR signal below 20 K is
also evident in the microwave power dependence of the intensity. The
power saturation at 30 K has a feature of a homogeneous spin system. On
the other hand, at 10 K, increasing the power above 200 ΜW doubles the
intensity suddenly and then it is easily saturated in the higher microwave
power range above 1 mW, showing inhomogeneity in the spin system.
Unlike the ESR intensity that represents the dynamical susceptibility, the
