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 ∼800 Oe 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.

Topics
Magnetic ordering, Magnetic fields, Semiconductor device fabrication, Magnetic materials, Scanning electron microscopy, Transmission electron microscopy, Nanoparticle, Nanotubes, Pyrolysis, Catalysts and Catalysis
1.
C. K.
 
Yang
,
J. J.
 
Zhao
, and
J. P.
 
Lu
,
Phys. Rev. Lett.
https://doi.org/10.1103/PhysRevLett.90.257203
 
90
,
257203
(
2003
).
Google Scholar
Crossref
Search ADS
PubMed
 
2.
Y. J.
 
Kang
,
J.
 
Choi
,
C. Y.
 
Moon
, and
K. J.
 
Chang
,
Phys. Rev. B
https://doi.org/10.1103/PhysRevB.71.115441
 
71
,
115441
(
2005
).
Google Scholar
Crossref
Search ADS
 
3.
S. Y.
 
Chou
,
Proc. IEEE
https://doi.org/10.1109/5.573754
 
85
,
652
(
1997
).
Google Scholar
Crossref
Search ADS
 
4.
T.
 
Arie
,
H.
 
Nishijima
,
S.
 
Akita
, and
Y.
 
Nakayama
,
J. Vac. Sci. Technol. B
https://doi.org/10.1116/1.591159
 
18
,
104
(
2000
).
Google Scholar
Crossref
Search ADS
 
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
).
Google Scholar
 
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
https://doi.org/10.1103/PhysRevB.65.113405
 
65
,
113405
(
2002
).
Google Scholar
Crossref
Search ADS
 
8.
N.
 
Grobert
,
W. K.
 
Hsu
,
Y. Q.
 
Zhu
,
J. P.
 
Hare
,
H. W.
 
Kroto
, and
D. R. M.
 
Walton
,
Appl. Phys. Lett.
https://doi.org/10.1063/1.125352
 
75
,
3363
(
1999
).
Google Scholar
Crossref
Search ADS
 
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.
https://doi.org/10.1063/1.1557824
 
93
,
7894
(
2003
).
Google Scholar
Crossref
Search ADS
 
10.
C.
 
Müller
,
S.
 
Hampel
,
D.
 
Elefant
,
K.
 
Biedermann
,
A.
 
Leonhardt
,
M.
 
Ritschel
, and
B.
 
Büchner
,
Carbon
https://doi.org/10.1016/j.carbon.2005.12.036
 
44
,
1746
(
2006
).
Google Scholar
Crossref
Search ADS
 
11.
D. C.
 
Wei
,
L. C.
 
Cao
,
L.
 
Fu
,
X. L.
 
Li
,
Y.
 
Wang
,
G.
 
Yu
, and
Y. Q.
 
Liu
,
Adv. Mater. (Weinheim, Ger.)
https://doi.org/10.1002/adma.200600885
 
19
,
386
(
2007
).
Google Scholar
Crossref
Search ADS
 
12.
C. N. R.
 
Rao
,
R.
 
Sen
,
B. C.
 
Satish kumar
, and
A.
 
Govindaraj
,
Chem. Commun. (Cambridge)
 
1998
,
1525
.
13.
S.
 
Iijima
,
Nature (London)
https://doi.org/10.1038/354056a0
 
354
,
56
(
1991
).
Google Scholar
Crossref
Search ADS
 
14.
M. S.
 
Dresselhaus
,
G.
 
Dresselhaus
, and
R.
 
Saito
,
Carbon
https://doi.org/10.1016/0008-6223(95)00017-8
 
33
,
883
(
1995
).
Google Scholar
Crossref
Search ADS
 
15.
E. H.
 
Frei
,
S.
 
Shtrikman
, and
D.
 
Treves
,
Phys. Rev.
https://doi.org/10.1103/PhysRev.106.446
 
106
,
446
(
1957
).
Google Scholar
Crossref
Search ADS
 
16.
S.
 
Chikazumi
,
Physics of Ferromagnetism
, 2nd ed. (
Oxford University Press
,
New York
,
1997
), Chap. 16.
Google Scholar
 
17.
J. A.
 
Osborn
,
Phys. Rev.
https://doi.org/10.1103/PhysRev.67.351
 
67
,
351
(
1945
).
Google Scholar
Crossref
Search ADS
 
18.
A.
 
Aharoni
,
IEEE Trans. Magn.
https://doi.org/10.1109/TMAG.1986.1064461
 
22
,
478
(
1986
).
Google Scholar
Crossref
Search ADS
 
19.
A.
 
Aharoni
,
J. Appl. Phys.
https://doi.org/10.1063/1.337354
 
60
,
1118
(
1986
).
Google Scholar
Crossref
Search ADS
 
20.
L. I.
 
Mendelsohn
,
F. E.
 
Luborsky
, and
T. O.
 
Paine
,
J. Appl. Phys.
https://doi.org/10.1063/1.1721888
 
26
,
1274
(
1955
).
Google Scholar
Crossref
Search ADS
 
21.
D.
 
Kechrakos
 and
K. N.
 
Trohidou
,
Phys. Rev. B
https://doi.org/10.1103/PhysRevB.58.12169
 
58
,
012169
(
1998
).
Google Scholar
Crossref
Search ADS
 
22.
E. C.
Stoner
 and
E. P.
Wohlfarth
 ,
Philos. Trans. R. Soc. London, Ser. A
https://doi.org/10.1098/rsta.1948.0007
 
240
,
599
(
1948
);
Crossref
Search ADS
Google Scholar
 
E. C.
 
Stoner
 and
E. P.
 
Wohlfarth
, Republished in
IEEE Trans. Magn.
https://doi.org/10.1109/TMAG.1991.1183750
.
27
,
3475
(
1991
).
Crossref
Search ADS
Google Scholar
 
23.
L.
 
Sun
,
Y.
 
Hao
,
C. L.
 
Chien
, and
P. C.
 
Searson
,
IBM J. Res. Dev.
 
49
,
79
(
2005
).
Google Scholar
Crossref
Search ADS
 
24.
T. O.
 
Paine
,
L. I.
 
Mendelsohn
, and
F. E.
 
Luborsky
,
Phys. Rev.
https://doi.org/10.1103/PhysRev.100.1055
 
100
,
1055
(
1955
).
Google Scholar
Crossref
Search ADS
 
© 2008 American Institute of Physics.
2008
American Institute of Physics
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