Effect of magnetic field on the electrodeposition of FeCo layers has been investigated with respect to the orientation of the magnetic field to surface electrode e.g magnetic field is parallel and perpendicular to electrode. Electrochemical behaviours, morphology, composition, structure and magnetic properties were investigated using cyclic voltammogram (CV), Scanning Electron Microscopy (SEM), Energy Dispersion Spectroscopy (EDS), X-Ray Diffractometer (XRD), Vibrating Sample Magnetometer (VSM). Results show that morphology and structure of the deposited layers are not effected by external magnetic field. Meanwhile, the Fe content of the layer decreases by following sequence CFe(B=0)CFe(B//)CFe(^), resulting in the following sequence of coerciviy HC(B=0) HC (B//) HC (^). These results were explained based on the magnetohydronamic (MHD) effect caused by the Lorentz force () when magnetic field is superimposed

Anh Dung, Dang Viet

Truong, Nguyen Xuan

Tung, Mai Thanh

English

Vietnam Academy of Science and Technology: Journals Online

 591
Journal of Chemistry, Vol. 47 (5), P. 591 - 595, 2009 
 
INFLUENCE OF MAGNETIC FIELD ON PROPERTIES OF 
ELECTRODEPOSITED FeCo LAYER 
Received 21 November 2008 
MAI THANH TUNG1, DANG VIET ANH DUNG1, NGUYEN XUAN TRUONG2 
1Dep. of Electrochemistry and Corrosion Protection, Hanoi University of Technology 
2Dep. of Analytical Chemistry, Hanoi University of Technology 
 
ABSTRACT 
Effect of magnetic field on the electrodeposition of FeCo layers has been investigated with 
respect to the orientation of the magnetic field to surface electrode e.g magnetic field is parallel 
and perpendicular to electrode. Electrochemical behaviours, morphology, composition, structure 
and magnetic properties were investigated using cyclic voltammogram (CV), Scanning Electron 
Microscopy (SEM), Energy Dispersion Spectroscopy (EDS), X-Ray Diffractometer (XRD), 
Vibrating Sample Magnetometer (VSM). Results show that morphology and structure of the 
deposited layers are not effected by external magnetic field. Meanwhile, the Fe content of the 
layer decreases by following sequence CFe(B=0)>CFe(B//)>CFe(⊥), resulting in the following 
sequence of coerciviy HC(B=0)> HC (B//)> HC (⊥). These results were explained based on the 
magnetohydronamic (MHD) effect caused by the Lorentz force ( LF
→
) when magnetic field is 
superimposed. 
 
I - INTRODUCTION 
Soft magnetic films are essentially applied 
for thin-film recording heads to meet the future 
trends in high-density magnetic recording. For 
this purpose, it is necessary to develop recording 
heads using material with optimized magnetic 
and corrosion properties. Three groups of 
magnetic films can be distinguished: nickel – 
iron, cobalt – iron, and ternary alloys 
composed of cobalt – iron and a third element 
like nickel, copper, or chromium [1-5]. The 
electrochemical deposition of these films seems 
to be technologically interesting since the 
electrodeposition is a fast, cost effective 
technique and suitable for covering of large 
areas and applicable to mass production. It is 
known that magnetic fields (B) influence the 
process of electrodeposition of layers [6-8]. The 
explanation of the influence of magnetic field is 
mainly based on the magnetohydronamic 
(MHD) effect caused by the Lorentz force 
( LF
→
).    However, influences of magnetic field 
on the structure, composition, morphology and 
magnetic properties of electrodeposited 
magnetic layers have so far been studied only 
on few systems [6 - 9].  
In this paper, we present results of study on 
the influence of a uniform magnetic field with 
different orientation to electrode surface on the 
magnetic properties of the electrodeposited 
FeCo layers. 
II - EXPERIMENTAL 
Electrochemical investigations were carried 
out by means of potentiostatic technique using 
potentiostat (Jaissle). All potentials are 
measured vs. the saturated Ag/AgCl reference 
 592
electrode (SSE). The FeCo layers were deposited 
from 0.02 M FeSO4 and 0.2 M CoSO4 with 
addition of 0.1 M Na2SO4 as a supporting 
electrolyte. A pH value of 3 was adjusted with 
H2SO4. The substrates 100 nm Cu on Si (100) – 
wafer with 5 nm Ta seed layer were used as the 
working electrode. Homogeneous magnetic 
fields of 700 mT strength have been applied in 
the gap of an electromagnet. Two different 
magnetic field to electrode configurations have 
been investigated. In the first configuration, the 
surface is parallel to magnetic field and in the 
second configuration, electrode surface is 
perpendicular to magnetic field.  
Surface morphology of the obtained 
electrodeposited layers was investigated using 
scanning Electron Microscopy (SEM). The 
composition of the alloys was determined by 
Energy Dispersion Spectroscopy (EDS). Texture 
and phase formation of the films were analyzed 
by X-ray Diffractometer (XRD). Magnetic 
hysteresis loop and magnetic coercivity Hc of 
the electrodeposited layers were measured using 
Vibrating Sample Magnetometer (VSM).   
III - RESULTS AND DISCUSSION 
Fig. 1 displays the cyclovoltammogram of 
the substrate Cu (111) without magnetic field 
(B=0) (curve a), with B = 700 mT parallel to the 
surface (curve b) and with B = 700 mT 
perpendicular to the surface (curve c). In the 
forward scan, the electrodeposition of the FeCo 
layers occurs at – 1300 mV/SSE. In the reverse 
scan, the anodic dissolution of the formed CoFe 
layers appears at – 950 mV. It is interesting to 
note that the current density increases in the 
presence of external magnetic field and the 
perpendicular configuration results higher 
current density than the parallel mode.
  
-2000 -1800 -1600 -1400 -1200 -1000 -800 -600 -400 -200 0
-80
-60
-40
-20
0
20
40
60
80
100
Fe
FeCo alloy
(a) 0T
(b) 700mT per
(c) 700mT par
i /
m
A
.c
m
-2
E/V vs SSE
(b)
(a)
(c)
 
Fig. 1:  Cyclic Voltammetry curves without B (curve a) and with B = 700 mT parallel to the surface 
(curve b) and with B = 700 mT perpendicular to the surface (curve c). 
 
Fig. 2 shows SEM images of the CoFe 
deposited at a cathodic potential of –1400 
mV/SSE without an applied magnetic field, as 
well as with parallelly and perpendicularly 
oriented applied magnetic field of 700 mT. 
Results show that the morphology of the FeCo 
deposits does not change significantly as 
magnetic field is applied. In both cases with and 
without magnetic field, FeCo deposits show 
quite visible grains. 
Fig. 3 displays XRD pattern of the 
electrodeposited FeCo layers without B and with 
superimposed magnetic field B = 700 mT. It can 
be observed that the electrodeposited layers are 
solid solution with the basic fcc phase ((111) 
texture) of Co. No appearance of other 
structures is found in the XRD spectra of 
electrodeposited FeCo layers under external 
 593
magnetic fields oriented parallelly and perpendicularly.
       
      
 
(a) B = 0 T (b) B = 700 mT parallel to the surface 
 
(c) B = 700 mT perpendicular to the surface 
Fig. 2: SEM images of electrodeposited FeCo layers in solutions (a) B = 0 T; (b) B = 700 mT  
parallel to the surface; (c) B = 700 mT perpendicular to the surface. 
 
Fig. 3: XRD pattern of electrodeposited FeCo layers (a) B = 0 T; (b) B = 700 mT parallel to the 
surface (curve b)(c) B = 700 mT perpendicular to the surface 
 594
Composition (wt.%) of FeCo films obtained 
by EDS are shown in Tab. 1. It can be seen that 
Co content increases or, in other words, Fe 
content decreases as magnetic field is applied, 
and the Fe content with parallel configuration is 
higher than that of the perpendicular 
configuration (CFe(B=0)>CFe(B//)>CFe(⊥)). This 
result indicates that the magnetic field influences 
clearly on the deposition mechanism, which 
resulting in the change of alloy composition.
 
Tab. 1: Composition (wt.%) and magnetic coercivity (Hc) of FeCo layers electrodeposited with  
B = 0 T and with different orientation of the magnetic field (B = 700 mT) 
B (mT)  
0 700 parallel 700 perpendicular 
Composition (wt.%) 
Co 
Fe 
 
84% 
16% 
 
87% 
13% 
 
88% 
12% 
Magnetic coercivity Hc (Oe) 65 63 59 
 
This behaviour can be explained by 
magnetohydronamic (MHD) effect. When 
magnetic field B is parallel to the electrode 
surface, MHD effect is re strong [6, 8]. The 
origin of this effect lies in the Lorentz 
force, LF j B
→ → →= × , where j is the current density 
and B is the magnetic field. During the 
electrolysis, this force acts on the migration of 
ions and induced a convective flow of the 
electrolyte close to the electrode surface [6,8]. 
The largest convection generated by B-oriented 
perpendicularly to the electrode surface supports 
the desorption of hydrogen bubbles, which leads 
to a change of the hydrodynamic conditions in 
the solution. On the contrary, when a magnetic 
is applied parallel to the electrode surface, the 
Lorentz force is zero. As a result, hydrogen 
evolution reaction occurs more easily for the 
perpendicular mode. Moreover, since hydrogen 
evolution reaction is related to the formation of 
M(OH)x compound (M = Fe, Co), which in turn 
relates to the reduction of Fe and Co to form the 
FeCo alloy, Co content for perpendicular 
configuration is higher than that for parallel 
configurationand with magnetic field B=0.
 
 
Fig. 4: Hysteresis loops of FeCo layers electrodeposited from solutions B = 0 T (curve a); B = 700 
mT parallel to the surface (curve b); B = 700 mT perpendicular to the surface (curve c) 
 595
In order to examine the magnetic properties 
of the obtained layers, hysteresis loops were 
recorded (Fig. 4). The magnetic coercivity Hc of 
layers obtained from Fig. 4 are shown in Tab. 1. 
It can be seen that coercivity (Hc) decreases by 
following sequence: HC(B = 0)> HC (B//)> HC 
(⊥). This behavior is directly related to the 
change in the composition of electrodeposited 
films since structure and morphology of the 
films do not change with external magnetic 
fields. A correlation between the composition 
and soft magnetic properties reveals that softer 
magnetic properties are achieved when 
electrodeposition processes is carried out with 
external magnetic field.  
IV - CONCLUSIONS 
Influence of magnetic field with two 
configurations (i) parallel to electrode and (ii) 
perpendicular to electrode were investigated. 
Results showed that the magnetic field with 
both configurations did not influence on the 
surface technology and crystal structure of the 
deposited film. Meanwhile, the magnetic field 
and magnetic to surface configuration 
influenced remarkably on the alloy composition, 
namely Fe content decreased as magnetic field 
was applied, and the Fe content with parallel 
configuration was higher than that of the 
perpendicular configuration (CFe (B = 0) > 
CFe(B//) > CFe(⊥)). The changes in the 
composition of obtained layers could be 
explained by magnetohydrodynamic (MHD) 
effect by Lorentz force. As a result, magnetic 
coercivity (Hc) decreases by following 
sequence: HC (B = 0)> HC (B//)> HC (⊥). 
Acknowledgements: The authors thank 
Ministry of Science and Technology for 
financial support of this work (project KHCB. 
5.028.06). The author also wish to acknowledge 
German Academic Exchange Agency (DAAD) 
and Leibniz Institut fuer Festkoeper- und 
Werkstoffforschung Dresden (IFW) for 
supporting this work. 
REFERENCES 
1.   K. M. Yin, S. L. Jan. Surf. Coat. Technol., 
79, 252 - 262 (1996). 
2. F. Lallemand, L. Ricq, P. Bercot, J. Pagetti. 
Electrochim. Acta, 47, 4149 - 4156 (2002). 
3. I. Tabakovic, V. Inturi, S. Riemer. J. 
Electrochem. Soc., 149, C18 - C22 (2002). 
4. M. P. Gigandet, F. X. Perrin, J. Pagetti, G. 
Poupon. Mater. Corr., 51, 1 - 6 (2000).  
5. J. M. Maire, G. Poupon, J. Pagetti, M. P. 
Gigandet, Electrochem. Soc. Proc. Ser.- 
Pennington, 98,  519 - 530 (1999). 
6.  A. Krause, M. Uhlemann, A. Gebert, L. 
Schultz. Electrochim. Acta, 49, 4127 - 4134 
(2004). 
7.  A. Krause, C. Hamann, M. Uhlemann, A. 
Gebert, L. Schultz. J. Magnetism and 
Magnetic Materials 290 - 291, 261 - 264 
(2005). 
8.   A. Krause, M. Uhlemann, A. Gebert, L. 
Schultz. Thin Solid Films, 515, 1694 - 1700 
(2006). 
9.   Mai Thanh Tung, Nguyen Hoang Nghi. J. 
Chemistry, 45, 97 (2007). 
    
 
Corresponding author: Mai Thanh Tung 
Dep. of Electrochemistry and Corrosion Protection,  
Hanoi University of Technology. 
 


Influence of magnetic field on properties of electrodeposited FeCo layer

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Influence of magnetic field on properties of electrodeposited FeCo layer

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