To tune the coercivity of Fe-filled carbon-nanotube (CNT) arrays, the shape anisotropy of encapsulated Fe nanoparticles (Fe-NPs) was investigated. Four Fe-filled CNT-array samples with different Fe-NP aspect ratios were prepared by catalytic pyrolysis of acetylene using ferrocene as catalyst. The coercivity of the Fe-filled CNT arrays increased from 300 to 800Oe at room temperature when the mean aspect ratio of the encapsulated Fe-NPs changed from 1.6 to 6.0. This clear dependence of the coercivity of the Fe-filled CNT arrays on the aspect ratio of the Fe-NPs might be interpreted in terms of the Stoner–Wohlfarth model. This result indicates that changing the shape anisotropy of the encapsulated Fe-NPs is an effective method to tune the coercivity of the Fe-filled CNTs.

1.
C. K.
Yang
,
J. J.
Zhao
, and
J. P.
Lu
,
Phys. Rev. Lett.
90
,
257203
(
2003
).
2.
Y. J.
Kang
,
J.
Choi
,
C. Y.
Moon
, and
K. J.
Chang
,
Phys. Rev. B
71
,
115441
(
2005
).
3.
S. Y.
Chou
,
Proc. IEEE
85
,
652
(
1997
).
4.
T.
Arie
,
H.
Nishijima
,
S.
Akita
, and
Y.
Nakayama
,
J. Vac. Sci. Technol. B
18
,
104
(
2000
).
5.
I.
Mönch
,
A.
Meye
,
A.
Leonhardt
,
K.
Krämer
,
R.
Kozhuharova
,
T.
Gemming
,
M. P.
Wirth
, and
B.
Büchner
,
J. Magn. Magn. Mater.
290–291
,
276
(
2005
).
7.
C.
Prados
,
P.
Crespo
,
J. M.
González
,
A.
Hernando
,
J. F.
Marco
,
R.
Gancedo
,
N.
Grobert
,
M.
Terrones
,
R. M.
Walton
, and
H. W.
Kroto
,
Phys. Rev. B
65
,
113405
(
2002
).
8.
N.
Grobert
,
W. K.
Hsu
,
Y. Q.
Zhu
,
J. P.
Hare
,
H. W.
Kroto
, and
D. R. M.
Walton
,
Appl. Phys. Lett.
75
,
3363
(
1999
).
9.
T.
Mühl
,
D.
Elefant
,
A.
Graff
,
R.
Kozhuharova
,
A.
Leonhardt
,
I.
Mönch
,
M.
Ritschel
,
P.
Simon
,
S.
Groudeva-Zotova
, and
C. M.
Schneider
,
J. Appl. Phys.
93
,
7894
(
2003
).
10.
C.
Müller
,
S.
Hampel
,
D.
Elefant
,
K.
Biedermann
,
A.
Leonhardt
,
M.
Ritschel
, and
B.
Büchner
,
Carbon
44
,
1746
(
2006
).
11.
D. C.
Wei
,
L. C.
Cao
,
L.
Fu
,
X. L.
Li
,
Y.
Wang
,
G.
Yu
, and
Y. Q.
Liu
,
Adv. Mater. (Weinheim, Ger.)
19
,
386
(
2007
).
12.
C. N. R.
Rao
,
R.
Sen
,
B. C.
Satish kumar
, and
A.
Govindaraj
,
Chem. Commun. (Cambridge)
1998
,
1525
.
13.
S.
Iijima
,
Nature (London)
354
,
56
(
1991
).
14.
M. S.
Dresselhaus
,
G.
Dresselhaus
, and
R.
Saito
,
Carbon
33
,
883
(
1995
).
15.
E. H.
Frei
,
S.
Shtrikman
, and
D.
Treves
,
Phys. Rev.
106
,
446
(
1957
).
16.
S.
Chikazumi
,
Physics of Ferromagnetism
, 2nd ed. (
Oxford University Press
,
New York
,
1997
), Chap. 16.
17.
18.
A.
Aharoni
,
IEEE Trans. Magn.
22
,
478
(
1986
).
19.
A.
Aharoni
,
J. Appl. Phys.
60
,
1118
(
1986
).
20.
L. I.
Mendelsohn
,
F. E.
Luborsky
, and
T. O.
Paine
,
J. Appl. Phys.
26
,
1274
(
1955
).
21.
D.
Kechrakos
and
K. N.
Trohidou
,
Phys. Rev. B
58
,
012169
(
1998
).
22.
E. C.
Stoner
and
E. P.
Wohlfarth
,
Philos. Trans. R. Soc. London, Ser. A
240
,
599
(
1948
);
E. C.
Stoner
and
E. P.
Wohlfarth
, Republished in
IEEE Trans. Magn.
.
27
,
3475
(
1991
).
23.
L.
Sun
,
Y.
Hao
,
C. L.
Chien
, and
P. C.
Searson
,
IBM J. Res. Dev.
49
,
79
(
2005
).
24.
T. O.
Paine
,
L. I.
Mendelsohn
, and
F. E.
Luborsky
,
Phys. Rev.
100
,
1055
(
1955
).
You do not currently have access to this content.