Chin. Phys. B Vol. 19, No. 8 (2010) 087502
Micromagnetic simulation on the dynamic susceptibility
spectra of cobalt nanowires arrays: the effect of
magnetostatic interaction
∗
Chen Wen-Bing(陈文兵), Han Man-Gui(韩满贵)
†
, Zhou Hao(周 浩),
Ou Yu(欧 雨), and Deng Long-Jiang(邓龙江)
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China,
Chengdu 610054, China
(Received 10 May 2009; revised manuscript received 2 March 2010)
Micromagnetic simulations have been performed to obtain the dynamic susceptibility spectra of 4×4 cobalt
nanowire arrays with different spatial configurations and geometries. The susceptibility spectra of isolated wires have
also been simulated for comparison purposes. It is found that the susceptibility spectrum of nanowire array bears a
lot of similarities to that of an isolated wire, such as the occurrences of the edge mode and the bulk resonance mode.
The simulation results also reveal that the susceptibility spectrum of nanowire array behaves like that of single isolated
wire as the interwire distance grows to an extent, which is believed due to the decrease of magnetostatic interaction
among nanowires, and can be further confirmed by the static magnetic hysteresis simulations. In comparison with single
nanowire, magnetostatic interaction may increase or decrease the resonance frequencies of nanowire arrays assuming a
certain interwire distance when the length of array increases. Our simulation results are also analysed by employing
the Kittel equation and recent theoretical studies.
Keywords: micromagnetic simulation, dynamic susceptibility, nanowire array, magnetostatic inter-
action
PACC: 7540G, 7540M, 3240, 7500
1. Introduction
The potential applications of magnetic nanowire
(NW) arrays in perpendicular magnetic recording in-
dustry and microwave devices have stimulated numer-
ous researches to investigate their static and dynamic
magnetic properties.
[1−13]
However, the tendency to
reduce the dimension of NW arrays and their con-
stituents gives rise to a new problem: magnetostatic
interaction among NWs, which plays a crucial role es-
pecially when the separation between adjacent NWs
is greatly shortened. Many works have pointed out
that the static magnetic properties of NWs are af-
fected by magnetostatic interaction between NWs.
For instance, it has been shown that strong magne-
tostatic interaction in magnetic NW arrays could lead
to an antiferromagnetic ground state (checkerboard
pattern)
[4−6]
and the magnetostatic interaction field
in low aspect ratio CoP cylinder nanoarrays is strong
enough to exceed the switching field of the elements
in the arrays.
[7]
Recent studies on the magnetization
reversal behaviour of high density cobalt NW arrays
reveal that the magnetostatic interaction field between
NWs increases not only with NW diameters but also
with NW lengths.
[8]
A second facet concerning magnetic NW arrays is
their dynamic properties. Among them, the dynamic
susceptibility spectrum of NW arrays is of great im-
portance in both fundamental and application fields.
One attribute that makes this property desirable is
that the eddy current loss interfering with susceptibil-
ity spectrum is greatly suppressed for nanowires.
[9−11]
Another reason is that the resonance frequency of the
uniform gyromagnetic mode for NW arrays can be
tuned by varying the aspect ratio and material, apply-
ing dc fields, and changing the porosity of membranes
in which NWs are embedded.
[12]
The last method is
thoroughly discussed in Refs. [12] and [13], indicat-
ing that dipolar interaction between NWs has a great
impact on the resonance frequency of NW array.
As an important technique to investigate the dy-
namic properties of nanostructured materials,
[14−25]
micromagnetics is fueled by the growing calculation
speed of computers. However, the simulation on NW
∗
Project supported by the National Natural Science Foundation of China (Grant No. 60701016) and the National Natural Science
Foundation of China–the Royal Society of United Kingdom International Jointed Project (Grant No. 60911130130).
†
Corresponding author. E-mail: mangui@gmail.com
c
2010 Chinese Physical Society and IOP Publishing Ltd
http://www.iop.org/journals/cpb
http://cpb.iphy.ac.cn
087502-1