Effect of geometrical parameters on the magnetic
properties of bilayered Co/Ni patterned arrays
N. Deshpande1*, A. Shelke1, A. Patil1, J. Hwang2, W. Pong3 and Y. Lee2#
1
Department of Physics, Shivaji University, Kolhapur-416004 M.S. India.
q-Psi and Department of Physics, Hanyang University, Seoul 133-791, S. Korea
3
Department of Physics, Tamkang University, Tamsui 251, Taiwan.
Corresponding author:* nicedeshpande@rediffmail.com; # yplee@hanyang.ac.kr
2
Abstract
Bilayer (BL) Co (patterned)/Ni (unpatterned) antidot
arrays have been fabricated with antidot diameter of 700
and 800 nm, having different symmetries, i.e., square and
rhomboid lattices. Systematic studies on the in-plane as
well as the out-of-plane anisotropy and the switching-field
properties were carried out. The SQUID measurements
showed that the inclusion of holes/defects in the uniform
upper magnetic layer, with modified lattice geometry and
antidot size, helps in changing the domain configuration,
thereby drastically affecting the switching fields. Soft
magnetic properties were obtained in such BL structures,
which were different from their single layer magnetic
antidot counterparts.
Also, the coercivity was observed to be different within
the square and rhomboid lattice samples. might be due
to the fact that the smaller size antidots have higher
magnetostatic and/or exchange interaction energy as
compared to larger-sized antidot samples.
Keywords: Magnetic arrays, magnetic reversals, switching
fields, SQUID, magnetic properties.
Introduction
Magnetic
nano/micro-structures
have
experienced a rapid progress in field of spintronics and
data storage [1-3]. Perforated magnetic medias like
antidot arrays having antidot geometries with proper
choice i.e., size, separation, lattice symmetry/orientation
and formation of multilayers, one can have a control
over the magnetic properties [2-3]. Hence, in the present
work we tried to design and fabricate different-diameter
as well as different-symmetry antidot arrays of bilayer
(BL) Co/Ni magnetic structures, and studied their effect
on the magnetic properties. From here onwards we use
sample abbreviations as S1 and S2 for square lattice,
and R1 and R2 for rhomboid lattice, having antidot
diameter of 700 and 800 nm, respectively.
Thin layers of Co and Ni on Si substrate were
subsequently deposited using dc sputtering unit. The
patterning was done by photolithography technique only
over the upper Co layer of 40 nm thickness, while the 5
nm thick Ni layer was kept unpatterned. Typical AFM
images of the Co/Ni antidot arrays with different lattice
geometries are shown in Fig. 1 (a-d). It was seen that
the coercivity and the relative remanence (Mr/Ms) was
higher in case of rhomboid lattice (R1 and R2) as
compared to the square lattice (S1 and S2) samples.
FIG. 1. AFM images of: (a) S1 (10×10 m2), (b) S2
(10×10 m2), (c) R1 (5×5 m2) and (d) R2 (5×5 m2)
samples. Insets are the line profile images.
TABLE 1. GP calculated for the BL sample from the
AFM studies
Sample Name
S1
S2
R1
R2
Thickness
(nm)
45 ± 5
45 ± 5
45 ± 5
45 ± 5
Diameter (nm)
700 ± 10
800 ± 10
700 ± 10
800 ± 10
References
[1] C. C. Wang, et al., Nanotechnology 17, 1629
(2006).
[2] S. Tehrani, et al., IEEE Trans. Magn. 36, 2752
(2000).
[3] N. G. Deshpande et al., IEEE Trans.Magn. 47,
2515 (2011).
[4] N. G. Deshpande et al., Appl. Phys. Lett. 96,
122503 (2010).