The magnetic properties of (Co0.97Al0.03)0.7Fe0.3 nanowires electrodeposited at different frequency of 50-
1000 Hz were studied. This nanowires were prepared by alternative current electrodeposition using porous
anodic aluminum oxide as template. The results show that coercivity of samples slightly increased with increasing
the frequency. Comparing the M–H hysteresis loops in different frequency shows that saturation
magnetization (Ms) per unit area decreases with increasing the frequency. Magnetic properties were also
investigated after annealing at 575 C. After annealing, a clear increase in coercivity was observed.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3534

Najafi, M.

Rafati, A.A.

Zare, A.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 4, 04MFPN08(2pp) (2012)   2304-1862/2012/1(4)04MFPN08(2) 04MFPN08-1  2012 Sumy State University Effect of Electrodeposition Frequency on Magnetic Properties of  (Co0.97Al0.03)0.7Fe0.3 Nanowires  M. Najafi1,*, A. Zare2,†, A.A. Rafati2,‡  1 Department of Materials Engineering, Hamedan University of Technology (HUT), Hamedan, Iran 2 Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P.O.Box 65174, Hamedan, Iran  (Received 19 June 2012; published online 23 August 2012)  The magnetic properties of (Co0.97Al0.03)0.7Fe0.3 nanowires electrodeposited at different frequency of 50-1000 Hz were studied. This nanowires were prepared by alternative current electrodeposition using porous anodic aluminum oxide as template. The results show that coercivity of samples slightly increased with in-creasing the frequency. Comparing the M–H hysteresis loops in different frequency shows that saturation magnetization (Ms) per unit area decreases with increasing the frequency. Magnetic properties were also investigated after annealing at 575  C. After annealing, a clear increase in coercivity was observed.  Keywords: Nanowire, Magnetic properties, Electrodeposition, Frequency, Anodic aluminum oxide mem-brane (AAO).    PACS numbers: 75.75.Cd, 78.67.Uh                                                             * mojgannajafi1@gmail.com †atefehzare63@gmail.com ‡ rafati_aa@yahoo.com 1. INTRODUCTION  Metal nanostructures continue to attract considera-ble attention because of their size and shape-dependent catalytic, electronic, optical, and magnetic properties [1]. To date, various mesoporous materials such as pol-ycarbonate membranes [2], anodic oxide films of alumi-num [3], carbon nanotubes [4], and organic molecule networks [5] have been employed as templates for the fabrication of arrays of various materials by means of electroless, sol-gel, hydrothermal, solvothermal, chemi-cal vapor, and electrodeposition approaches. Using AAO films, the electrochemical deposition process is an attractive synthesis route for 1D nanostructures, providing a controllable and inexpensive method for the preparation of metallic nanowires with well-defined geometry[6]. In the present paper, we systematically investigate the effects of electrodeposition frequency and annealing on magnetic properties of (Co0.97Al0.03)0.7Fe0.3 nanowires.  2. EXPERIMENTAL  Anodic aluminum oxide membrane template were prepared by using a two-step anodization procedure. In the first anodization step, the polished Al foils were dc anodized in 0.3M oxalic acid at 40V for 15 h. Then, the formed oxide layer was removed by wet chemical etch-ing in a mixed solution of phosphoric acid and chromic acid. The sample was re-anodized for 1 h using the same parameters as in the first step. After tendering the barrier layer by reduce voltage systematically, elec-trodeposition was started. Porous aluminum oxide on the aluminum base was used as working electrode and platinum plate used as counter electrode. The Co-Al-Fe alloys were electrodeposited in the pores of the alumina templates at a constant potential. The peak to peak voltage and frequencies of the sine waveform used in ac electrodeposition were 30V and 50, 200, 400, 600, 800, and 1000 Hz, respectively. The electrolyte used to elec-trodeposit (Co0.97Al0.03)0.7Fe0.3 nanowires had the follow-ing composition: (190.9g/l of CoSO4.7H2O, 7.0g/l of Al2(SO4)3.18H2O, 83.4g/l of FeSO4.7H2O a 45 g/l boric acid and 1 g/l ascorbic acid), with pH value about 3. To study the effect of annealing on the crystallinity, the as-deposited samples were annealed in argon atmos-phere. It is noticeable that the optimum temperature and time were found to be 575°C and 30 min, respective-ly.Magnetic properties of the samples were measured using alternating gradient force magnetometer (AGFM).  3. RESULTS AND DISCUSSION  In a systematical investigation, the effects of differ-ent frequency of the ac electrodeposition as well as an-nealing on the magnetic properties of (Co0.97Al0.03)0.7Fe0.3 nanowires were studied.   0 200 400 600 800 100014001600180020002200240026002800Hc (Oe)frequenc (Hz) as-deposited annealed at 575oC  Fig. 1 – Coercivity and squareness of (Co0.97Al0.03)0.7Fe0.3 nan-owires deposited as a function ofelectrodeposition frequency and annealing    M. NAJAFI, A. ZARE, A.A. RAFATI PROC. NAP 1, 04MFPN08 (2012)   04MFPN08-2 As shown in Fig. 1, the coercivity slightly increases with increase in frequency from 50 Hz to 1000 Hz. The increase in coercivity after annealing is probably relat-ed to the change microstructure of samples during the annealing process. There is a sort of internal stress in the as-deposited samples induced by rapid electrodepo-sition of ions. Thermal annealing relieves the internal stress. A higher degree of crystallinity is also obtained by annealing. So the Hc of annealed sample is higher for annealed sample than that for as-deposited.   -4000 -2000 0 2000 4000-1.0-0.50.00.51.0M/AApplied field(Oe) 200 Hz 400 Hz 1000 Hz  Fig. 2 – Hysteresis loops of (Co0.97Al0.03)0.7Fe0.3 samples synthesized at 200, 400, 1000 Hz with sine waveform. Hysteresis loops were measured with the magnetic field appliedperpendicular (out of plane) to template surface  Comparing the hysteresis loop of samples synthe-sized at 200, 400, and 1000 Hz shows that saturation magnetization (Ms) per unit area with lower frequency is higher than those with higher frequency (Fig. 2). It is because the tunneling current decreased by increasing the frequency and then the amount of electrodeposited material is decreased. Root mean square of electrodep-osition current (Irms) during the (Co0.97Al0.03)0.7Fe0.3 nan-owires electrodeposition process increases by frequency but deposited material that depended to tunneling cur-rent (unsymmetrical part of negative current) decreas-es by frequency.  4. CONCLUSIONS:  The influences of ac electrodeposition frequency and annealing on the magnetic properties of high aspect ratio (Co0.97Al0.03)0.7Fe0.3 nanowires deposited into the alumina nanopores were investigated. This study ena-bles us to arrive at the following conclusion: 1. It was seen that increasing the frequency increased the coercivity and decreased the among of deposited material. 2. The high coercivity was obtained for samples pre-paredat 50Hz after annealing at 575°C in argon at-mosphere for 30 min.  AKNOWLEDGEMENT  The authors are grateful for the financial support from the Grant Research Councils of Bu-Ali Sina and HUT Universities.   REFERENCES   1. D.Q. Gao, X.Q. Zhou, Y. Xu, Z.H. Zhang, D.S. Xue, Solid State Commun. 150, 127 (2010). 2. J.K.N. Mbindyo, T. E.Mallouk, J. B.Mattzela, et al., J. Am. Chem. Soc.124 No15, 4020(2002). 3. H. Masuda, K. Fukuda, Science.268 No5216, 1466 (1995). 4. P.M. Ajayan, O. Stephan, Ph. Redlich, C. Colliex, Nature 375, No6532 564(1995). 5. T. Hassenkam, K. Nørgaard, L. Iversen, C.J. Kiely, M. Brust, T. Bjørnholm, Adv. Mater. 14 No16, 1126 (2002). 6. R. Bertholdo, M.C. Assis, P. Hammer, S.H. Pulcinelli, C.V. Santilli,J. Eur. Ceram. Soc. 30,181 (2010).  

Effect of Electrodeposition Frequency on Magnetic Properties of (Co0.97Al0.03)0.7Fe0.3 Nanowires

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 4, 04MFPN08(2pp) (2012) 
 
 
2304-1862/2012/1(4)04MFPN08(2) 04MFPN08-1  2012 Sumy State University 
Effect of Electrodeposition Frequency on Magnetic Properties of  
(Co0.97Al0.03)0.7Fe0.3 Nanowires 
 
M. Najafi1,*, A. Zare2,†, A.A. Rafati2,‡ 
 
1 Department of Materials Engineering, Hamedan University of Technology (HUT), Hamedan, Iran 
2 Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P.O.Box 65174, Hamedan, Iran 
 
(Received 19 June 2012; published online 23 August 2012) 
 
The magnetic properties of (Co0.97Al0.03)0.7Fe0.3 nanowires electrodeposited at different frequency of 50-
1000 Hz were studied. This nanowires were prepared by alternative current electrodeposition using porous 
anodic aluminum oxide as template. The results show that coercivity of samples slightly increased with in-
creasing the frequency. Comparing the M–H hysteresis loops in different frequency shows that saturation 
magnetization (Ms) per unit area decreases with increasing the frequency. Magnetic properties were also 
investigated after annealing at 575  C. After annealing, a clear increase in coercivity was observed. 
 
Keywords: Nanowire, Magnetic properties, Electrodeposition, Frequency, Anodic aluminum oxide mem-
brane (AAO). 
 
  PACS numbers: 75.75.Cd, 78.67.Uh 
 
 
                                                          
* mojgannajafi1@gmail.com 
†atefehzare63@gmail.com 
‡ rafati_aa@yahoo.com 
1. INTRODUCTION 
 
Metal nanostructures continue to attract considera-
ble attention because of their size and shape-dependent 
catalytic, electronic, optical, and magnetic properties 
[1]. To date, various mesoporous materials such as pol-
ycarbonate membranes [2], anodic oxide films of alumi-
num [3], carbon nanotubes [4], and organic molecule 
networks [5] have been employed as templates for the 
fabrication of arrays of various materials by means of 
electroless, sol-gel, hydrothermal, solvothermal, chemi-
cal vapor, and electrodeposition approaches. Using 
AAO films, the electrochemical deposition process is an 
attractive synthesis route for 1D nanostructures, 
providing a controllable and inexpensive method for the 
preparation of metallic nanowires with well-defined 
geometry[6]. In the present paper, we systematically 
investigate the effects of electrodeposition frequency 
and annealing on magnetic properties of 
(Co0.97Al0.03)0.7Fe0.3 nanowires. 
 
2. EXPERIMENTAL 
 
Anodic aluminum oxide membrane template were 
prepared by using a two-step anodization procedure. In 
the first anodization step, the polished Al foils were dc 
anodized in 0.3M oxalic acid at 40V for 15 h. Then, the 
formed oxide layer was removed by wet chemical etch-
ing in a mixed solution of phosphoric acid and chromic 
acid. The sample was re-anodized for 1 h using the 
same parameters as in the first step. After tendering 
the barrier layer by reduce voltage systematically, elec-
trodeposition was started. Porous aluminum oxide on 
the aluminum base was used as working electrode and 
platinum plate used as counter electrode. The Co-Al-Fe 
alloys were electrodeposited in the pores of the alumina 
templates at a constant potential. The peak to peak 
voltage and frequencies of the sine waveform used in ac 
electrodeposition were 30V and 50, 200, 400, 600, 800, 
and 1000 Hz, respectively. The electrolyte used to elec-
trodeposit (Co0.97Al0.03)0.7Fe0.3 nanowires had the follow-
ing composition: (190.9g/l of CoSO4.7H2O, 7.0g/l of 
Al2(SO4)3.18H2O, 83.4g/l of FeSO4.7H2O a 45 g/l boric 
acid and 1 g/l ascorbic acid), with pH value about 3. 
To study the effect of annealing on the crystallinity, 
the as-deposited samples were annealed in argon atmos-
phere. It is noticeable that the optimum temperature 
and time were found to be 575°C and 30 min, respective-
ly.Magnetic properties of the samples were measured 
using alternating gradient force magnetometer (AGFM). 
 
3. RESULTS AND DISCUSSION 
 
In a systematical investigation, the effects of differ-
ent frequency of the ac electrodeposition as well as an-
nealing on the magnetic properties of (Co0.97Al0.03)0.7Fe0.3 
nanowires were studied. 
 
 
0 200 400 600 800 1000
1400
1600
1800
2000
2200
2400
2600
2800
H
c
 (
O
e
)
frequenc (Hz)
 as-deposited
 annealed at 575
o
C
 
 
Fig. 1 – Coercivity and squareness of (Co0.97Al0.03)0.7Fe0.3 nan-
owires deposited as a function ofelectrodeposition frequency 
and annealing  
 
 M. NAJAFI, A. ZARE, A.A. RAFATI PROC. NAP 1, 04MFPN08 (2012) 
 
 
04MFPN08-2 
As shown in Fig. 1, the coercivity slightly increases 
with increase in frequency from 50 Hz to 1000 Hz. The 
increase in coercivity after annealing is probably relat-
ed to the change microstructure of samples during the 
annealing process. There is a sort of internal stress in 
the as-deposited samples induced by rapid electrodepo-
sition of ions. Thermal annealing relieves the internal 
stress. A higher degree of crystallinity is also obtained 
by annealing. So the Hc of annealed sample is higher 
for annealed sample than that for as-deposited. 
 
 
-4000 -2000 0 2000 4000
-1.0
-0.5
0.0
0.5
1.0
M
/A
Applied field(Oe)
 200 Hz
 400 Hz
 1000 Hz
 
 
Fig. 2 – Hysteresis loops of (Co0.97Al0.03)0.7Fe0.3 samples 
synthesized at 200, 400, 1000 Hz with sine waveform. 
Hysteresis loops were measured with the magnetic field 
appliedperpendicular (out of plane) to template surface 
 
Comparing the hysteresis loop of samples synthe-
sized at 200, 400, and 1000 Hz shows that saturation 
magnetization (Ms) per unit area with lower frequency 
is higher than those with higher frequency (Fig. 2). It is 
because the tunneling current decreased by increasing 
the frequency and then the amount of electrodeposited 
material is decreased. Root mean square of electrodep-
osition current (Irms) during the (Co0.97Al0.03)0.7Fe0.3 nan-
owires electrodeposition process increases by frequency 
but deposited material that depended to tunneling cur-
rent (unsymmetrical part of negative current) decreas-
es by frequency. 
 
4. CONCLUSIONS: 
 
The influences of ac electrodeposition frequency and 
annealing on the magnetic properties of high aspect 
ratio (Co0.97Al0.03)0.7Fe0.3 nanowires deposited into the 
alumina nanopores were investigated. This study ena-
bles us to arrive at the following conclusion: 
1. It was seen that increasing the frequency increased 
the coercivity and decreased the among of deposited 
material. 
2. The high coercivity was obtained for samples pre-
paredat 50Hz after annealing at 575°C in argon at-
mosphere for 30 min. 
 
AKNOWLEDGEMENT 
 
The authors are grateful for the financial support 
from the Grant Research Councils of Bu-Ali Sina and 
HUT Universities. 
 
 
REFERENCES 
 
 
1. D.Q. Gao, X.Q. Zhou, Y. Xu, Z.H. Zhang, D.S. Xue, Solid 
State Commun. 150, 127 (2010). 
2. J.K.N. Mbindyo, T. E.Mallouk, J. B.Mattzela, et al., J. Am. 
Chem. Soc.124 No15, 4020(2002). 
3. H. Masuda, K. Fukuda, Science.268 No5216, 1466 (1995). 
4. P.M. Ajayan, O. Stephan, Ph. Redlich, C. Colliex, Nature 
375, No6532 564(1995). 
5. T. Hassenkam, K. Nørgaard, L. Iversen, C.J. Kiely, 
M. Brust, T. Bjørnholm, Adv. Mater. 14 No16, 1126 (2002). 
6. R. Bertholdo, M.C. Assis, P. Hammer, S.H. Pulcinelli, 
C.V. Santilli,J. Eur. Ceram. Soc. 30,181 (2010). 
 


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Effect of Electrodeposition Frequency on Magnetic Properties of (Co0.97Al0.03)0.7Fe0.3 Nanowires

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