In this work presented results of magneto-optic Kerr effect experimental investigations in rhin-film systems based on Ni and V and also on Co (10 nm), Fe20Ni80 (20 nm) films and Co(10)/Fe20Ni80(20)/S double-plate as a sensitive elements of magnetic film transmitters. Were shown dimensional and temperature dependencies of this effect. It was estimated a correlation between magneto-optical properties and multilayer systems composition

Bibyk, Vitalii Volodymyrovych

Hrychanovska, Tetiana Mykhailivna

Lytvynenko, Ia.M.

Sheshenia, L.A.

Бибик, Виталий Владимирович

Бібик, Віталій Володимирович

Гричановская, Татьяна Михайловна

Гричановська, Тетяна Михайлівна

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 3 No 1, 01NTF06(3pp) (2014) 
 
 
2304-1862/2014/3(1)01NTF06(3) 01NTF06-1  2014 Sumy State University 
Magnetooptical Properties of Film Systems Based on Ferromagnetic Materials 
 
T.M. Grychanovska, L.A. Sheshenia*, Ia.M. Lytvynenko, V.V. Bibyk 
 
Sumy State University, 2, Rymskogo-Korsakova Str., 40007 Sumy, Ukraine 
 
(Received 29 May 2014; published online 29 August 2014) 
 
The results of experimental studies of the magnetooptical Kerr effect of thin-film systems based on Ni 
and V, as well as film Ni80Fe20 and Ni40Fe10Co50 alloys as sensitive elements of magnetic field sensors are 
presented. Dimensional and temperature dependencies of the Kerr effect are shown. A correlation between 
magnetooptical properties and changes in the structure of multilayer systems based on Ni and V is 
established. The negligible fluctuation of the magnetic parameters (BC and BS) of Ni-Fe samples depending 
on the thickness and annealing temperature was found. In contrast to this, Ni-Fe-Co films demonstrated a 
significant change of MOKE-loop shape at different annealing temperatures, that confirms the occurrence 
of phase transitions in the film samples. 
 
Keywords: Magnetooptical properties, Kerr effect, Coercivity, MOKE, Thin film, Saturation field, 
Hysteresis loop, Alloy 
 
 PACS numbers: 68.37.Lp, 64.70.Kd, 78.66.Bz  
 
 
                                                          
*chibyshevaliubov@gmail.com  
1. INTRODUCTION 
 
Unique magnetic, transport and optical properties 
of nanodimensional film systems, such as 
ferromagnetic material / nonmagnetic metal have 
attracted much interest because of their application in 
nanoelectronics. Magnetization process in 
ferromagnetic materials is mostly governed by 
competition between three types of interactions: 
exchange interaction, magnetocrystalline anisotropy, 
and magnetic dipolar interaction [1]. Minimization of 
the total magnetic energy determines the stable 
magnetization configuration. During the magnetization 
reversal in thin films, magnetic domains of opposite 
direction start to nucleate and then propagate across 
the sample as a magnetic field B, is swept through BC. 
One of methods to observe the detailed mechanisms of 
magnetization reversal is a spectrometry of the 
magnetooptic Kerr effect (MOKE) [1]. Although no 
direct information can be obtained regarding the 
absolute magnitude of the magnetization, the angle of 
Kerr rotation is directly proportional to the 
magnetization [2, 3] and make possible to finding such 
parameters like coercivety BC, saturation field BS and 
relative magnetization changes of the samples.  
Film systems based on the soft ferromagnetic 
metals (Co, Ni, Fe) and their alloys (Ni-Fe, Ni-Fe-Co 
etc.) are known because their extensive using of 
magnetic, magnetostrictive and magnetoresistive 
properties for creating the sensitive elements of sensor 
technology, for example, in magnetic recording heads or 
highly sensitive measuring devices [4, 5]. 
The results of experimental studies of the 
magnetooptical properties dependence on the system 
composition and the annealing temperature for 
multylayer film systems based on Ni and V and the 
magnetooptical properties dependence on film 
thickness and annealing temperature for the film Ni-Fe 
and Ni-Fe-Co alloys are presented in this paper. 
 
2. EXPERIMENT 
 
Series of films were deposited in an oil vapor-free 
vacuum of ~ 10 – 4 Pa by thermoresistive and electron 
gun methods of deposition. Three-layered 
Ni(15 nm)/V(15 nm)/Ni(40 nm)/S or 
Ni(15 nm)/V(1.5 nm)/Ni(40 nm)/S structures and 
multilayer film systems with periodical structure 
[Ni(1.5 nm)/V(1.5 nm)]n (n  1-4) were obtained by Ni 
and V layer-by-layer deposition on glass-ceramic 
substrates (S). Films deposition was carried out to 
substrate at Ts  320 K and after were annealed at 
Ta ≤ 600 K. The bulk permalloy 79NM (cNi ~ 80 %) was 
used for receiving of Ni-Fe thin films. A series of Ni-Fe-
Co films were deposited on the amorphous substrates 
by thermoresistive technique by co-evaporation using 
permalloy 79NM and Co independent sources at room 
temperature. The Fe-Ni-Co alloy was deposited on 
substrate before heated to 500 K. All samples were 
annealed within temperature range 500-1000 K for 
20 minutes. Samples size is 10 × 10 mm2. The films 
thickness was controlled by quartz resonator or 
interferometer. The chemical composition of the 
obtained Ni-Fe-Co alloy was calculated based on weight 
of the deposited components, and further controlled by 
energy-dispersive X-ray spectroscopy (EDX) with an 
error of ± 5 %. The component concentration in the Ni-
Fe and Ni-Fe-Co alloys is in at.%: cNi  80, cFe  20 and 
cNi  40, cFe  10, cCo  50 respectively. Magnetooptical 
measurements were carried out in longitudinal 
geometry (magnetic field is applied in the film plane 
and parallel to the plane of light beam incidence). Kerr 
angle value (θk) measuring was estimated by zero-
analyze technique using a twice modulation of fallen 
light yield polarization by azimuth on magnetooptic 
device (inductivity field value was ≤ 150 mT).  
 
3. RESULTS AND DISCUSSION  
 
MOKE hysteresis loop for multilayer film system 
 T.M. GRYCHANOVS’KA, L.A. SHESHENIA, ET AL. PROC. NAP 3, 01NTF06 (2014) 
 
 
01NTF06-2 
[Ni (1.5 nm) / V (1.5 nm)]n and Ni (15 nm) /V (15 nm) / 
Ni (40 nm) are shown in Fig. 1. Further investigation of 
obtained dependencies shown that as-deposited 
multilayer systems (n  1-2) in magnetic field ± 150 mT 
have a weak MOKE value (θk  0.1 mrad) and its 
intensity almost was not depend on annealing. It may 
be caused by solid solutions formation during the films 
system condensation. At n  4 the MOKE signal of as-
deposited and annealed at 600 К patterns  increased in 
several times (θk  0.2-0.4 mrad) at simultaneously 
increasing of their coercivity to 5 mT. In case of three-
layered Ni (15 nm) / V(15 nm) / Ni (40 nm) / S and 
Ni (15 nm) /V (1.5 nm) / Ni (40 nm) / S film systems the 
MOKE signals are considerably higher compare to 
[Ni(1.5 nm)/ V(1.5 nm)]n structures. It was estimated 
that as-deposited three-layered 
Ni (15 nm) / V (15 nm) / Ni (40 nm) / S film system has 
the maximum value of Kerr angle (θk  15 mrad) in 
magnetic field ± 150 mT. Its demagnetization 
inductivity BC and saturation inductivity BS have 
values 10 mT and 25 mT respectively. Different 
parameters ratio of top and bottom ferromagnetic 
layers may significantly influence on the shape of 
hysteresis loops and their magnetic reversal nature [6]. 
An inhomogeneous magnetic reversal was observed for 
the annealed at 600 K Ni(15 nm)/V(15 nm)/Ni(40 nm)/S 
film system which can be caused by soft magnetic and 
hard magnetic independent reversal. An analysis of 
hysteresis curve (magnetic switching effect) shown that 
antiferromagnetic distribution in this system is not 
stable in our point of view [6]. 
Magnetooptical Kerr effect of the Ni80Fe20 film sam-
ples with different thickness and annealing tempera-
ture is shown on the Fig. 2. Well known that the bulk 
Ni80Fe20 alloy is magnetically soft with high 
permeability in low magnetic fields with saturation 
induction 0.65-0.75 T. The MOKE signal analysis of 
Ni80Fe20 alloy samples showed their strong sensitivity 
to the film thickness (Fig. 2a). Thus, by increasing the 
thickness of the sample from 17 to 23 nm, the coercivity 
of the film increases by 1.5 times. But the greatest 
value of the demagnetization induction BC  5 mT was 
found for 10 nm film thickness, that can be explained 
by the possible heterogeneity of the sample material. 
Hysteresis loops have almost rectangular shape with a 
sharp reversal when the sample orientation is parallel 
to the magnetic field. Rectangular hysteresis loop 
(Fig. 2) is typical for easy magnetization, indicating the 
presence of a plane of easy magnetization reversal 
which is parallel to the plane of the sample. The results 
are close to experimental studies of permalloy and Co 
in the works of Weber et al. [7-9]. 
 
-150 -100 -50 0 50 100 150
-0,50
-0,25
0,00
0,25
0,50

k
 (
m
ra
d
)
B (mT)
1  Ta= 320 K
2  Ta= 600 K
a
1
2
 
-150 -100 -50 0 50 100 150
-8
-6
-4
-2
0
2
4
6
8
1  Ta= 320 K
2  Ta= 600 K
b

k
 (
m
ra
d
)
B (mT)
1
2
 
 
Fig. 1 – MOKE hysteresis loop for multilayer film system [Ni (1.5 nm) / V (1.5 nm)]n (а) and three-layer film system 
Ni (15 nm) / V (15 nm) / Ni (40 nm) (b) deposited on substrate heated to 320 K (loops “1”) and annealed to 600 К (loops “2”) 
 
-15 -10 -5 0 5 10 15
-1
0
1
3
2
N
o
rm
a
li
z
e
d
 M
O
K
E
 s
ig
n
a
l 
(a
.u
.)
B (mT)
1  23 nm
2  17 nm
3  10 nm
1
a
 
-10 -5 0 5 10
-1
0
1
4
3
2
N
o
rm
a
li
z
e
d
 M
O
K
E
 s
ig
n
a
l 
(a
.u
.)
B (mT)
1  300 K
2  500 K
3  700 K
4  900 K
1
b
 
 
Fig. 2 – Normalized MOKE signal as a function of films thickness (a) and annealing temperature (b) for Fe20Ni80 film samples. 
The samples of 23 nm thickness were annealed 
 
 MAGNETOOPTICAL PROPERTIES OF FILM SYSTEMS… PROC. NAP 3, 01NTF06 (2014) 
 
 
01NTF06-3 
Annealing of permalloy thin film samples with 
thickness 23 nm in the temperature range 300-900 K 
weakly reflected on MOKE signals (Fig. 2 b), that 
indicate an immutability of the structural and phase 
composition of the samples. (More detail about 
determine the concentration, study of the crystal 
structure and phase composition of Ni-Fe and Ni-Fe-Co 
thin films see Ref. [10, 11]). The decreasing of BC after 
annealing at 500 K is a consequence of the 
thermostabilization process, namely reducing the 
number of defects, which contribute to retardation the 
domain walls propagation at magnetization reversal 
[12]. A slight increase of saturation field and coercivity 
(a few mT) was observed with further heat treatment 
at 700-900 K that can be a consequence of the grain 
size increasing. Besides, the reason for fluctuations in 
the BC values possibly is a presence of small magnetic 
anisotropy in the sample plane as a result of sample 
preparation technique [11]. 
Normalized MOKE signal for ternary film alloy 
Ni40Fe10Co50 with 45 nm thickness is shown in Fig.3. 
MOKE loop of the as-deposited film (Fig. 3, loop 1) does 
not have a sharp magnetization reversal which 
suggests the presence of several phases with different 
magnetic parameters that the effect on the domain 
structure of the sample and its magnetization reversal 
processes. After annealing at 900 K (Fig. 3, loop 2) the 
MOKE loop changes shape on the rectangular. 
Coercivity and saturation field increased by 57 % and 
36 %, respectively.  
 
-25 -20 -15 -10 -5 0 5 10 15 20 25
-1
0
1
4
3
2
1  500 K
2  900 K
3  1000 K
4  Polar
 geometry
N
o
rm
a
li
z
e
d
 M
O
K
E
 s
ig
n
a
l 
(a
.u
.)
B (mT)
1
 
Fig. 3 – Normalized MOKE signal for ternary film alloy 
Ni40Fe10Co50 (45 nm) deposited on heated to 500 K (1) 
substrate and annealed at 900 (2) and 1000 K (3). MOKE 
signal measured in polar geometry 
A significant change of the magnetic parameters 
indicates a change in the phase state of the Ni-Fe-Co 
alloy, namely the formation of a solid solution [11]. 
Heat treatment of the sample at 1000 K (Fig. 3, loop 3) 
causes a decrease of BC and the saturation field 
disappearance within the applied magnetic field, 
thereby approaching the magnetization loop to the 
form of hard magnetization reversal. As we reported 
previously [11] Ni-Fe-Co film loses its integrity and 
emptinesses appear in its volume after annealing 
temperature 1000 K, besides there is a considerable 
grains increasing that in total can be the reason of such 
magnetic behavior of the sample.  
The MOKE measurement results in the polar 
geometry (the applied magnetic field is perpendicular 
to the sample plane and parallel to the plane of light 
beam incidence) are typical for hard plane of 
magnetization reversal (Fig. 3, loop 4). 
 
4. CONCLUSIONS 
 
In this article we discussed the results of experi-
mental studies of magnetooptical properties of multi-
layer systems based on Ni / V with different numbers of 
layers, Ni80Fe20 and Ni40Fe10Co50 alloys with different 
thickness at different annealing temperatures. 
MOKE signals of annealed at 600 K film system 
Ni (15 nm) / V (15 nm) / Ni (40 nm) / S showed signifi-
cant heterogeneity of magnetization reversal process of 
the samples, that can be explained by the independent 
magnetization reversal soft and hard layers. 
The negligible fluctuation of the magnetic parame-
ters (BC and BS) of Ni80Fe20 samples depending on the 
thickness and annealing temperature was found. In 
contrast to this, Ni40Fe10Co50 films demonstrated a 
drastic change of MOKE loop shape at different anneal-
ing temperatures that confirm the occurrence of phase 
transitions in the film samples, namely the formation 
of a solid solution. 
A wide range of coercivity and character of magnet-
ization reversal process of samples may be available by 
combination a number of layers in the film systems 
[Ni / V]n, the thickness change of the individual layers 
or by condensation conditions and heat treatment as in 
the case of ternary Ni-Fe-Co alloy that make its prom-
ising for practical use in the manufacture of magnetic 
sensor elements, read/write heads and magnetoresis-
tive memory. 
 
 
REFERENCES 
 
1. S.-B. Choe, D.-H. Kim, Y.-C. Cho, H.-J. Jang, K.-S. Ryu, 
H.-S. Lee, S.-C. Shin, Rev. Sci. Instrum. 73, 2910 (2002). 
2. J.C. Suits, IEEE T. Magn. 8, 95 (1972). 
3. M.J. Freiser, IEEE T. Magn. 4, 152(1968). 
4. D.G. Rancourt, Phys. Canada 45, 3 (1995). 
5. G. Herzer, IEEE T. Magn. 26 No 5, 1397 (1990). 
6. K.A. Zvezdyn, Solid State Phys., 42 No 1, (2000). 
7. W. Weber, C.H. Back, A. Bischof, Ch. Wursch, 
R. Allenspach, Phys. Rev. Lett. 76, 1940 (1996). 
8. W. Weber, R. Allenspach, A. Bischof, Appl. Phys. Lett. 70 
520 (1997). 
9. C.M. Fu, P.C. Kao, M.S. Tsai, H.S. Hsu, C.C. Yu, 
J.C.A. Huang, J. Magn. Magn. Mater. 239, 17 (2002). 
10.  Z.M. Makukha, O.V. Synashenko, Ia.M. Lytvynenko, 
Yu.M. Shabelnyk, I.Yu. Protsenko, Promising innovations 
in science, education, production and transport 2012, ISSN 
2224-0187, 64 (Odessa: Kuprienko: 2012). [in Russian]. 
11. Ia.M. Lytvynenko, I.M. Pazukha, V.V. Bibyk, J. Nano- 
Electron. Phys. 6 No 2, 02014 (2014). [in Ukrainian]. 
12. G.S. Kandaurova, Sorosovskii Obrozovatelnyi J. 1, 127 
(1997).(Russ.) 


Magnetooptical Properties of Film Systems Based on Ferromagnetic Materials

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 3 No 1, 01NTF06(3pp) (2014)   2304-1862/2014/3(1)01NTF06(3) 01NTF06-1  2014 Sumy State University Magnetooptical Properties of Film Systems Based on Ferromagnetic Materials  T.M. Grychanovska, L.A. Sheshenia*, Ia.M. Lytvynenko, V.V. Bibyk  Sumy State University, 2, Rymskogo-Korsakova Str., 40007 Sumy, Ukraine  (Received 29 May 2014; published online 29 August 2014)  The results of experimental studies of the magnetooptical Kerr effect of thin-film systems based on Ni and V, as well as film Ni80Fe20 and Ni40Fe10Co50 alloys as sensitive elements of magnetic field sensors are presented. Dimensional and temperature dependencies of the Kerr effect are shown. A correlation between magnetooptical properties and changes in the structure of multilayer systems based on Ni and V is established. The negligible fluctuation of the magnetic parameters (BC and BS) of Ni-Fe samples depending on the thickness and annealing temperature was found. In contrast to this, Ni-Fe-Co films demonstrated a significant change of MOKE-loop shape at different annealing temperatures, that confirms the occurrence of phase transitions in the film samples.  Keywords: Magnetooptical properties, Kerr effect, Coercivity, MOKE, Thin film, Saturation field, Hysteresis loop, Alloy   PACS numbers: 68.37.Lp, 64.70.Kd, 78.66.Bz                                                              *chibyshevaliubov@gmail.com  1. INTRODUCTION  Unique magnetic, transport and optical properties of nanodimensional film systems, such as ferromagnetic material / nonmagnetic metal have attracted much interest because of their application in nanoelectronics. Magnetization process in ferromagnetic materials is mostly governed by competition between three types of interactions: exchange interaction, magnetocrystalline anisotropy, and magnetic dipolar interaction [1]. Minimization of the total magnetic energy determines the stable magnetization configuration. During the magnetization reversal in thin films, magnetic domains of opposite direction start to nucleate and then propagate across the sample as a magnetic field B, is swept through BC. One of methods to observe the detailed mechanisms of magnetization reversal is a spectrometry of the magnetooptic Kerr effect (MOKE) [1]. Although no direct information can be obtained regarding the absolute magnitude of the magnetization, the angle of Kerr rotation is directly proportional to the magnetization [2, 3] and make possible to finding such parameters like coercivety BC, saturation field BS and relative magnetization changes of the samples.  Film systems based on the soft ferromagnetic metals (Co, Ni, Fe) and their alloys (Ni-Fe, Ni-Fe-Co etc.) are known because their extensive using of magnetic, magnetostrictive and magnetoresistive properties for creating the sensitive elements of sensor technology, for example, in magnetic recording heads or highly sensitive measuring devices [4, 5]. The results of experimental studies of the magnetooptical properties dependence on the system composition and the annealing temperature for multylayer film systems based on Ni and V and the magnetooptical properties dependence on film thickness and annealing temperature for the film Ni-Fe and Ni-Fe-Co alloys are presented in this paper.  2. EXPERIMENT  Series of films were deposited in an oil vapor-free vacuum of ~ 10 – 4 Pa by thermoresistive and electron gun methods of deposition. Three-layered Ni(15 nm)/V(15 nm)/Ni(40 nm)/S or Ni(15 nm)/V(1.5 nm)/Ni(40 nm)/S structures and multilayer film systems with periodical structure [Ni(1.5 nm)/V(1.5 nm)]n (n  1-4) were obtained by Ni and V layer-by-layer deposition on glass-ceramic substrates (S). Films deposition was carried out to substrate at Ts  320 K and after were annealed at Ta ≤ 600 K. The bulk permalloy 79NM (cNi ~ 80 %) was used for receiving of Ni-Fe thin films. A series of Ni-Fe-Co films were deposited on the amorphous substrates by thermoresistive technique by co-evaporation using permalloy 79NM and Co independent sources at room temperature. The Fe-Ni-Co alloy was deposited on substrate before heated to 500 K. All samples were annealed within temperature range 500-1000 K for 20 minutes. Samples size is 10 × 10 mm2. The films thickness was controlled by quartz resonator or interferometer. The chemical composition of the obtained Ni-Fe-Co alloy was calculated based on weight of the deposited components, and further controlled by energy-dispersive X-ray spectroscopy (EDX) with an error of ± 5 %. The component concentration in the Ni-Fe and Ni-Fe-Co alloys is in at.%: cNi  80, cFe  20 and cNi  40, cFe  10, cCo  50 respectively. Magnetooptical measurements were carried out in longitudinal geometry (magnetic field is applied in the film plane and parallel to the plane of light beam incidence). Kerr angle value (θk) measuring was estimated by zero-analyze technique using a twice modulation of fallen light yield polarization by azimuth on magnetooptic device (inductivity field value was ≤ 150 mT).   3. RESULTS AND DISCUSSION   MOKE hysteresis loop for multilayer film system  T.M. GRYCHANOVS’KA, L.A. SHESHENIA, ET AL. PROC. NAP 3, 01NTF06 (2014)   01NTF06-2 [Ni (1.5 nm) / V (1.5 nm)]n and Ni (15 nm) /V (15 nm) / Ni (40 nm) are shown in Fig. 1. Further investigation of obtained dependencies shown that as-deposited multilayer systems (n  1-2) in magnetic field ± 150 mT have a weak MOKE value (θk  0.1 mrad) and its intensity almost was not depend on annealing. It may be caused by solid solutions formation during the films system condensation. At n  4 the MOKE signal of as-deposited and annealed at 600 К patterns  increased in several times (θk  0.2-0.4 mrad) at simultaneously increasing of their coercivity to 5 mT. In case of three-layered Ni (15 nm) / V(15 nm) / Ni (40 nm) / S and Ni (15 nm) /V (1.5 nm) / Ni (40 nm) / S film systems the MOKE signals are considerably higher compare to [Ni(1.5 nm)/ V(1.5 nm)]n structures. It was estimated that as-deposited three-layered Ni (15 nm) / V (15 nm) / Ni (40 nm) / S film system has the maximum value of Kerr angle (θk  15 mrad) in magnetic field ± 150 mT. Its demagnetization inductivity BC and saturation inductivity BS have values 10 mT and 25 mT respectively. Different parameters ratio of top and bottom ferromagnetic layers may significantly influence on the shape of hysteresis loops and their magnetic reversal nature [6]. An inhomogeneous magnetic reversal was observed for the annealed at 600 K Ni(15 nm)/V(15 nm)/Ni(40 nm)/S film system which can be caused by soft magnetic and hard magnetic independent reversal. An analysis of hysteresis curve (magnetic switching effect) shown that antiferromagnetic distribution in this system is not stable in our point of view [6]. Magnetooptical Kerr effect of the Ni80Fe20 film sam-ples with different thickness and annealing tempera-ture is shown on the Fig. 2. Well known that the bulk Ni80Fe20 alloy is magnetically soft with high permeability in low magnetic fields with saturation induction 0.65-0.75 T. The MOKE signal analysis of Ni80Fe20 alloy samples showed their strong sensitivity to the film thickness (Fig. 2a). Thus, by increasing the thickness of the sample from 17 to 23 nm, the coercivity of the film increases by 1.5 times. But the greatest value of the demagnetization induction BC  5 mT was found for 10 nm film thickness, that can be explained by the possible heterogeneity of the sample material. Hysteresis loops have almost rectangular shape with a sharp reversal when the sample orientation is parallel to the magnetic field. Rectangular hysteresis loop (Fig. 2) is typical for easy magnetization, indicating the presence of a plane of easy magnetization reversal which is parallel to the plane of the sample. The results are close to experimental studies of permalloy and Co in the works of Weber et al. [7-9].  -150 -100 -50 0 50 100 150-0,50-0,250,000,250,50k (mrad)B (mT)1  Ta= 320 K2  Ta= 600 Ka12 -150 -100 -50 0 50 100 150-8-6-4-2024681  Ta= 320 K2  Ta= 600 Kbk (mrad)B (mT)12  Fig. 1 – MOKE hysteresis loop for multilayer film system [Ni (1.5 nm) / V (1.5 nm)]n (а) and three-layer film system Ni (15 nm) / V (15 nm) / Ni (40 nm) (b) deposited on substrate heated to 320 K (loops “1”) and annealed to 600 К (loops “2”)  -15 -10 -5 0 5 10 15-10132Normalized MOKE signal (a.u.)B (mT)1  23 nm2  17 nm3  10 nm1a -10 -5 0 5 10-101432Normalized MOKE signal (a.u.)B (mT)1  300 K2  500 K3  700 K4  900 K1b  Fig. 2 – Normalized MOKE signal as a function of films thickness (a) and annealing temperature (b) for Fe20Ni80 film samples. The samples of 23 nm thickness were annealed   MAGNETOOPTICAL PROPERTIES OF FILM SYSTEMS… PROC. NAP 3, 01NTF06 (2014)   01NTF06-3 Annealing of permalloy thin film samples with thickness 23 nm in the temperature range 300-900 K weakly reflected on MOKE signals (Fig. 2 b), that indicate an immutability of the structural and phase composition of the samples. (More detail about determine the concentration, study of the crystal structure and phase composition of Ni-Fe and Ni-Fe-Co thin films see Ref. [10, 11]). The decreasing of BC after annealing at 500 K is a consequence of the thermostabilization process, namely reducing the number of defects, which contribute to retardation the domain walls propagation at magnetization reversal [12]. A slight increase of saturation field and coercivity (a few mT) was observed with further heat treatment at 700-900 K that can be a consequence of the grain size increasing. Besides, the reason for fluctuations in the BC values possibly is a presence of small magnetic anisotropy in the sample plane as a result of sample preparation technique [11]. Normalized MOKE signal for ternary film alloy Ni40Fe10Co50 with 45 nm thickness is shown in Fig.3. MOKE loop of the as-deposited film (Fig. 3, loop 1) does not have a sharp magnetization reversal which suggests the presence of several phases with different magnetic parameters that the effect on the domain structure of the sample and its magnetization reversal processes. After annealing at 900 K (Fig. 3, loop 2) the MOKE loop changes shape on the rectangular. Coercivity and saturation field increased by 57 % and 36 %, respectively.   -25 -20 -15 -10 -5 0 5 10 15 20 25-1014321  500 K2  900 K3  1000 K4  Polar geometryNormalized MOKE signal (a.u.)B (mT)1 Fig. 3 – Normalized MOKE signal for ternary film alloy Ni40Fe10Co50 (45 nm) deposited on heated to 500 K (1) substrate and annealed at 900 (2) and 1000 K (3). MOKE signal measured in polar geometry A significant change of the magnetic parameters indicates a change in the phase state of the Ni-Fe-Co alloy, namely the formation of a solid solution [11]. Heat treatment of the sample at 1000 K (Fig. 3, loop 3) causes a decrease of BC and the saturation field disappearance within the applied magnetic field, thereby approaching the magnetization loop to the form of hard magnetization reversal. As we reported previously [11] Ni-Fe-Co film loses its integrity and emptinesses appear in its volume after annealing temperature 1000 K, besides there is a considerable grains increasing that in total can be the reason of such magnetic behavior of the sample.  The MOKE measurement results in the polar geometry (the applied magnetic field is perpendicular to the sample plane and parallel to the plane of light beam incidence) are typical for hard plane of magnetization reversal (Fig. 3, loop 4).  4. CONCLUSIONS  In this article we discussed the results of experi-mental studies of magnetooptical properties of multi-layer systems based on Ni / V with different numbers of layers, Ni80Fe20 and Ni40Fe10Co50 alloys with different thickness at different annealing temperatures. MOKE signals of annealed at 600 K film system Ni (15 nm) / V (15 nm) / Ni (40 nm) / S showed signifi-cant heterogeneity of magnetization reversal process of the samples, that can be explained by the independent magnetization reversal soft and hard layers. The negligible fluctuation of the magnetic parame-ters (BC and BS) of Ni80Fe20 samples depending on the thickness and annealing temperature was found. In contrast to this, Ni40Fe10Co50 films demonstrated a drastic change of MOKE loop shape at different anneal-ing temperatures that confirm the occurrence of phase transitions in the film samples, namely the formation of a solid solution. A wide range of coercivity and character of magnet-ization reversal process of samples may be available by combination a number of layers in the film systems [Ni / V]n, the thickness change of the individual layers or by condensation conditions and heat treatment as in the case of ternary Ni-Fe-Co alloy that make its prom-ising for practical use in the manufacture of magnetic sensor elements, read/write heads and magnetoresis-tive memory.   REFERENCES  1. S.-B. Choe, D.-H. Kim, Y.-C. Cho, H.-J. Jang, K.-S. Ryu, H.-S. Lee, S.-C. Shin, Rev. Sci. Instrum. 73, 2910 (2002). 2. J.C. Suits, IEEE T. Magn. 8, 95 (1972). 3. M.J. Freiser, IEEE T. Magn. 4, 152(1968). 4. D.G. Rancourt, Phys. Canada 45, 3 (1995). 5. G. Herzer, IEEE T. Magn. 26 No 5, 1397 (1990). 6. K.A. Zvezdyn, Solid State Phys., 42 No 1, (2000). 7. W. Weber, C.H. Back, A. Bischof, Ch. Wursch, R. Allenspach, Phys. Rev. Lett. 76, 1940 (1996). 8. W. Weber, R. Allenspach, A. Bischof, Appl. Phys. Lett. 70 520 (1997). 9. C.M. Fu, P.C. Kao, M.S. Tsai, H.S. Hsu, C.C. Yu, J.C.A. Huang, J. Magn. Magn. Mater. 239, 17 (2002). 10.  Z.M. Makukha, O.V. Synashenko, Ia.M. Lytvynenko, Yu.M. Shabelnyk, I.Yu. Protsenko, Promising innovations in science, education, production and transport 2012, ISSN 2224-0187, 64 (Odessa: Kuprienko: 2012). [in Russian]. 11. Ia.M. Lytvynenko, I.M. Pazukha, V.V. Bibyk, J. Nano- Electron. Phys. 6 No 2, 02014 (2014). [in Ukrainian]. 12. G.S. Kandaurova, Sorosovskii Obrozovatelnyi J. 1, 127 (1997).(Russ.) 

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Magnetooptical Properties of Film Systems Based on Ferromagnetic Materials

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