1. International JournalElectronics and Communication Engineering & Technology (IJECET), ISSN
International Journal of of Electronics and Communication
IJECET
Engineering & Technology (IJECET) Volume 2, Issue 2, May-July (2011), © IAEME
0976 – 6464(Print), ISSN 0976 – 6472(Online)
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online)
Volume 2, Issue 2, May – July (2011), pp. 08-15 ©IAEME
© IAEME, http://www.iaeme.com/ijecet.html
ELECTROMAGNETIC STUDIES ON NANO-SIZED
MAGNESIUM FERRITE
A.M.BHAVIKATTI
Research scholar,
Dr.M.G.R University, Chennai-600095, INDIA
arvindbhavikatti@gmail.com
DR.SUBHASH KULKARNI
Jaypraksh Narayan College of Engineering,
Mahaboobnagar - 509001, INDIA
subhashsk@gmail.com
DR. ARUNKUMAR. LAGASHETTY
Appa Institute of Engineering and Technology,
Gulbarga – 580102, INDIA.
arun_lagshetty@yahoo.com
ABSTRACT
Nanosized spinel ferrite MgFe2O4 has been prepared by microwave synthesis
technique.The dielectric properties of this sample are studied in the frequency range
1KHz-1MHz and in the temperature range 0-7000 C. The effect of temperature and
frequency on ac conductivity, dielectric constant and dielectric loss have been
discussed in terms of hopping of charge carriers. Electrical properties of MgFe2O4
were measured and it was found that, it has low electrical conductivity.The έ and έ΄
curves at different temperatures for this sample show a higher dispersion in the low
frequency region.The dielctric constant decreases with increasing frequency and is
found to follow the Maxwell-Wagner interfacial polarization.Magnetic properties are
measured using a VSM and the corresponding hysteresis loop is obtained. It is
observed that, Q-factor obtained here is high (150) compared to the Q-factor obtained
in case of bulk ferrites.
Keywords: Microwave synthesis,Hysteresis loop,a.c.conductivity,dielectric constant,
Q-factor
1. INTRODUCTION
Magnesium ferrite (MgFe2O4) is an important magnetic oxide with spinel structure
[1]. Magnesium ferrite and allied compounds have found wide spread applications in
microwave devices because of their low magnetic and dielectric losses, and high
resistivites [2]. Synthesis of nano -sized MgFe2O4 is important for its magnetic
properties, particularly super paramagnetic behavior and super paramagnetic particles
and these can be used for different biomedical applications [3].
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME
Magnesioferrite (MgFe2O4) is a magnetic bi-oxide ceramic material with excellent
chemical stability. Magnetic dilution, due to the substitution of diamagnetic atoms,
gives rise to interesting magnetic features in compounds with spinel structure.
Although MgFe2O4 is a magnetic material, Mg2+ ions have no magnetic nature and the
phenomena of distribution of Mg2+ ions on the sites depend on the synthesis
temperature, directly affecting some magnetic properties, such as saturation
magnetization (MS) and transition temperature, which vary with the conditions of heat
treatments[4].
2. EXPERIMENTAL PROCEDURE
Here, microwave firing is used for synthesis of magnesium ferrite
materials.Nanosized MgFe2O4 is synthesized by microwave route using urea as a
fuel.Magnesium oxalates and iron oxalates were prepared by dissolving magnesium
and iron salt in oxalic acid solution.Then,these two oxalates are irradiated with
microwaves using urea as a fuel to get cubic MgFe2O4 nanoparticles.From XRD-data,
the formation of cubic phase MgFe2O4 was confirmed and IR spectra confirmed the
formation of spinel structure. Similarly, from the SEM image, the formation of nano-
sized magnesium ferrite is confirmed [5].
2.1 Preparation of pellets
The powders were crushed and ground finally to reduce it to small crystallites of
uniform size. Then the powder was pressed into different shapes for the studies. The
mixture was dried and a small amount of PVA binder was added to the powder .The
resulting powders were pressed by applying a pressure of 70 Mpa in a stainless steel
die to make pellets of 1cm diameter and 1cm thickness for dielectric measurements
and toroid shaped particles for magnetic measurements. Then some of the pellets
were polished to get a uniform parallel surface. These samples were polished to
remove any roughness present on the surfaces. Silver paste was coated on their
surfaces to enable them to act as good electrical contacts for measuring electrical and
dielectric properties. The binder burn off was carried out by a slow heating rate. These
toroid shaped pellets were used for VSM (vibrating sample magnetometer) magnetic
for measurements.
2.2 Instrumentation
The powder X-ray diffraction pattern was obtained from GEOL JDX-8P X-ray
diffractometer using Cu-Kα radiation. The morphology of the sample was obtained
from Leica Cambridge-440 scanning electron microscopy .Bonding in nickel ferrite
was obtained from Perkin-Elmer FTIR spectrophotometer (1000). The magnetic
characterization of toroid shaped pellets was done using Vibrating sample
magnetometer (VSM). A c conductivity measurements and dielectric property
investigation were carried out at room temperature over the different frequency using
Keithely high precision multimeter .The quality factor (Q) was obtained from the
LCR-Q precision meter (Model HP-4192A)
3. MAGNETIC PROPERTIES
To find saturation magnetization, coercivity, remanance and other related parameters,
M-H curves are obtained with Foner vibrating sample magnetometer. The values of
saturation magnetization, MS, remanance ,Mr, coercivity, HC for MgFe2O4 have been
determined and are listed in Table-1 below.
Table -1
Sample Hc (Oe) Mr (emu / gm) Ms(emu / gm) Wt.
Mg Fe2O4 785.12 6.82 10.80 0.500 gm
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME
3.1 Hysteresis loop: Fig (1) shows the M-H curve of magnesium ferrite. The area of
the hysteresis loop corresponds to energy loss per unit volume per cycle.
Ferromagnetic materials, which have tall, narrow hysteresis loops with small loop
areas, are referred to as ‘soft’ ferrites. Good permanent magnets, on the other hand,
should show a high resistance to demagnetization. This requires that they be made
with materials that have large coercive field intensities HC and hence fat hysteresis
loops. These materials are referred to as ‘hard’ ferromagnetic materials .From Table-
1, the value of HC is found to be785.12 Oe and as per this magnesium ferrite may be
considered as the hard magnetic material.
Fig (1) Hysteresis loop of magnesium ferrite
4. DIELECTRIC MEASUREMENTS
The dielectric behavior for the present samples can be explained on the basis that the
mechanism of polarization process in ferrites is similar to that of conduction process
[6].
4.1Ac conductivity [σ ac]: The ac conductivity was measured at four different
frequencies 1 KHz, 10 KHz, 100 KHz and 1 MHz as shown in fig (2).From fig (2), it
is observed that, the ac conductivity decreases with increasing frequencies. A fall in σ
ac is observed at higher frequencies .Similarly, the effect of temperature on the ac
conductivity of magnesium ferrite were studied in the temperature range 00C-7000C.
It was observed that, the ac conductivity increases with the increase of temperature
ensuring the semiconducting nature of the sample [7] till reaching a maximum, then,
ac conductivity decreases to a minimum. Peaks of ac conductivity were observed to
shift towards higher temperature indicating a fall in conductivity. Very low
conductivity is observed for this sample at all temperatures and frequencies.
4.2Dielectric constant [ε´]: It can be seen from fig (3) that, the value of ε’ decreases
ε
with increasing frequency. This is a normal dielectric behavior of ferrimagnetic
materials, which may be due to the interfacial polarization as predicted by Maxwell –
Wagner (Wagner 1913). Similarly, it can be seen from fig (3) that, ε’ increases with
increasing temperature, until reaching a maximum then decreases with further
increase in temperature.
The dielectric dispersion in ferrites can be explained on the basis of space charge
polarization by the Maxwell-Wagner model. The applied voltage on the sample drops
mainly across the grain boundaries, causing localized accumulation of charge under
the influence of an electric field. The space charge in ferrites comes predominantly
from the electron hopping between Fe2+ and Fe3+. In ferrites the solids consist of well-
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME
conducting grains separated by poorly conducting grain boundaries. The electrons
reach the grain boundaries by hopping and if the resistance of the grain boundary is
high enough, electrons pile up and produce polarization at these places. With an
increase of the frequency of the applied field, the electrons reverse their direction
more often; even the electron exchange between Fe2+ and Fe3 ion pairs cannot follow
the change of the external applied field above a certain frequency. These effects result
in a decrease in the probability of electrons reaching the grain boundaries and
reducing the polarization of electrons. Therefore, the dielectric constant ε' decreases
with an increase of the frequency [8].
It is observed that the dielectric constant increases with the increase in temperature.
This increase is quite significant at lower frequencies in comparison to higher
frequencies. It is known that the dielectric constant of ferrites, in general, is dependent
on dipolar, interfacial, ionic and electronic polarizations. Dipolar and interfacial
polarizations play important role at lower frequencies and are temperature dependent.
At higher frequencies, ionic and electronic polarizations contribute to the dielectric
constant and are temperature independent .Therefore, in the present ferrites, the
significant increase in dielectric constant at lower frequencies with temperature arises
from the dipolar and interfacial polarizations [9].
4.3 Dielectric loss [ε´´]
ε
All dielectric materials have two types of losses .One is the conduction loss,
representing the flow of actual charges through the dielectric material. The other
dielectric loss is due to the movement of rotation of the atoms in an alternating field.
The variation of dielectric loss ε” with temperature at different frequencies is shown
in fig (4).The variation of ε” with different frequencies shows expected dispersion
behavior i.e. it decreases with increasing frequency. The ε” show dispersion in the
low frequency region, which is attributed to domain wall motion. At higher
frequencies, the losses are found to be low if domain wall motion is inhibited and
magnetization is forced to change by rotation .Similarly, the variation of ε” with
temperature also follows the expected trend i.e. in general, ε” increases with
increasing temperature and is explained basis of interfacial and space
polarization[10].
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME
-3
Cond
1.2x10
0.30 conductivity
-3
1.0x10
0.25
8.0x10
-4
(a) (b)
0.20
σac S/cm
-4
σac S/cm
6.0x10 0.15
-4
4.0x10 0.10
2.0x10
-4 0.05
0.0 0.00
0 100 200 300 400 500 600 700
0 100 200 300 400 500 600 700
0
0 Temperature C
Temperature in C
0.16 0.10
Cond Cond
0.14
( c) 0.08
(d)
0.12
0.10
0.06
0.08
σac S/cm
σac S/cm
0.06 0.04
0.04
0.02
0.02
0.00 0.00
-0.02
0 100 200 300 400 500 600 700 0 100 200 300 400 500 600 700
0 0
Temperature C Temperature C
Fig (2) Shows the variation of ac conductivity [ σ ac] with temperature at selected
frequencies [a]1KHz [b] 10KHz [c] 100KHz and [d]1MHz
11
5x10 7
6x10
E' E'
11 7
4x10 5x10
(a) (b)
7
3x10
11 4x10
7
3x10
ε'
ε'
11
2x10
7
2x10
11
1x10
7
1x10
0
0
0 100 200 300 400 500 600 700 0 100 200 300 400 500 600 700
0 0
Temperature C Temperature C
E'
6
3.5x10 E' 3500
6
3.0x10
3000
6
2.5x10
2500
2.0x10
6 ( c) (d)
2000
6
1.5x10
ε'
ε'
1500
6
1.0x10
1000
5
5.0x10
500
0.0
0
5
-5.0x10
0 100 200 300 400 500 600 700 0 100 200 300 400 500 600 700
0
Temperature C 0
Temperature in C
Fig (3) shows the variation of dielectric constant ε΄ with temperature at selected
frequencies [a] 1KHz [b] 10KHz [c] 100KHz and [d] 1MHz
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME
E''
10
6x10
E'' 1000
10
5x10
10
800
4x10
10 600
3x10
ε''
ε ''
2x10
10 (a) 400 (b)
10
1x10 200
0
0
0 100 200 300 400 500 600 700
0 100 200 300 400 500 600 700
0
Temperature C 0
Temperature in C
E''
-6
3.5 3.5x10
E''
-6
3.0 3.0x10
-6
2.5 2.5x10
-6
2.0 2.0x10
-6
ε ''
1.5 1.5x10
ε''
-6
1.0 1.0x10
0.5
( c) 5.0x10
-7 (d)
0.0 0.0
-7
-0.5 -5.0x10
0 100 200 300 400 500 600 700 0 100 200 300 400 500 600 700
0 0
Temperature C Temperature in C
Fig (4) Shows the variation of dielectric loss ε” with temperature at selected
frequencies [a] 1 KHz [b] 10 KHz [c] 100KHz and [d] 1MHz
-Q
Q-factor
160 75
140 70
120
(a) 65
(b)
100 60
Q-factor
80 55
Q-factor
60 50
40 45
20 40
0 35
-20 30
-100 0 100 200 300 400 500 600 700
0 100 200 300 400 500 600
Temperature
Temperature
-Q Q
70
50
60
40
50
(c) (d)
40 30
Q-factor
Q-factor
30
20
20
10
10
0
0
-100 0 100 200 300 400 500 600 700 -100 0 100 200 300 400 500 600 700
Temperature Temperature
Fig (5) Variation of Q-factor of nano-sized magnesium ferrite with temperature at selected
frequencies [a] 1 KHz [b] 10KHz [c] 100KHz and [d] 1MHz
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7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME
4.4 Q-factor studies
The variation of Q-factor with temperature at different frequencies is shown in fig (5).
Nano-sized magnesium ferrite was synthesized by the microwave synthesis. The Q-
factor obtained here is 150 at a frequency of 1 KHz and temperature of 2000 C. It is
observed that, Q-factor decreases with the increase of frequency and reaches 50 at a
frequency of 1MHz. This behavior agrees with the results reported earlier [11].The
nature of the variation of Q-factor with frequency also agrees with the results obtained
earlier [12].From the SEM of the nano-sized magnesium ferrite, it is observed that,
particle size is spherical in shape and not large with less number of pores. Due to all
these reasons, Q-factor remains high for this sample. But, it is worth noting that, the
Q-factor values in the whole frequency range 1KHz-IMHz are high compared to the
values obtained in the case of nano- ferrites as reported earlier [13].Further, Q-factor
values reported for this sample are for the pellets that were sintered in microwave
oven for much shorter duration(5mins)than those reported earlier
5. CONCLUSIONS
The magnesium ferrite nanoparticles were prepared by using a domestic microwave
oven without any refluxing system .The yield, grain size and other characteristics
observed indicate that the method followed in the present study can be considered as
suitable and economical one. Very low ac conductivity was observed for this sample.
The frequency dependent dielectric constant shows a large degree of dispersion
(5×1011) at low frequency, but rapid polarization is observed at high frequencies. High
dielectric losses (5×1010) are observed at low frequencies. Loss decreases with
increasing frequencies which is a normal behavior. Q-factor obtained here is in the
range of 150.So, this sample may find applications in good quality chip inductors and
it may be investigated further.
REFERENCES
[1] A.Goldman, Modern Ferrite Technology, Van Nostrand, New York ,1990
[2] K.S.Rane, V.M.S.Vernekar,P.Y.Sawant,Bull.Mater.Sci.Vol.24,No 3,June 2001,
323.
[3] Chen.Q ,Zhang.z.J ,Appl.Phys.Lett,73,3156(1998)
[4] S.F. Mansour, M.A. Elkestawy “A comparative study of electric properties of
nano-structured and bulk Mn–Mg spinel ferrite”, Ceramics International 37,
pp1175–1180, 2011.
[5] A.M.Bhavikatti, Subhash Kulkarni, Arunkumar.Lagashetty ,” Microwave firing
for Synthesis of nano-sized magnesium ferrite, Journal of Ultra Scientist of
Physical Sciences,Vol.21(1),pp9-14, 2009.
[6] A.N.Patil, M.G.Patil, K.K.Patanka,V.L.Mathe,B.P.Mahajan,S.A.Patil,
Bull.Mater.Sci.Vol.23,No 5,October , pp448, 2000.
[7] S. Da Dalt, A.S. Takimi , T.M. Volkmer ,V.C. Sousa , C.P. Bergmann, “
Magnetic and Mössbauer behavior of the nanostructured MgFe2O4 spinel
obtained at low temperature”, Powder Technology, 210, pp103–108,2011.
[8] Jian-Ping Zhou, Li Lv , Xian-Zhi Chen “ Dielectric and magnetic properties of
ZnO-doped cobalt ferrite”, Journal of Ceramic Processing Research, Vol. 11,
No. 2, pp. 263-272, 2010.
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8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME
[9] Navneet Singh, AshishAgarwal, SujataSanghi, ParamjeetSingh, “Effect of
magnesium substitution on dielectric and magnetic properties of Ni–Zn ferrite”,
Physica B, 406, pp 687–692, 2011.
[10] Abdelmoneim.H.M, “Dielectric properties of Tix Li1-xLa0.1Fe1.9O4 ferrite thin
films”, Indian Journal of Pure & Applied Physics, Vol.48, pp562-570, 2010.
[11] S R Murthy, “Low temperature sintering of MgCuZn ferrite and its electrical
and magnetic properties,” Bull. Mater. Sci., Vol. 24, No. 4, August 2001, pp.
379.
[12] Hsing-i hsiang, Hsin-hwa duh,“Effects of glass addition on sintering and
magnetic properties of 3Ba0.5Sr0.5O.2CoO.12Fe2O3 for high frequency
applications”, Journal Of Materials Science ,36 ,pp2081 – 2087,2001.
[13] W.C.Hsu ,S.C.Chen, P.C.Kuo ,C.T.Lie,W.S.Tsat, “ Preparation of NiCuZn
ferrite nanoparticles from chemical co-precipitation method and the magnetic
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142-149, 2004.
BIOGRAPHIES OF AUTHORS
A M Bhavikatti received a degree in Electronics & communication in
1985, has completed ME in power electronics in 1991 and is a research
scholar in Electronic materials .Till date, he has more than 35
publications in International and National journals and Conferences .He
is also a reviewer for a journal. Presently he is a Professor and Head of
Electronics and Communication Engineering Dept at Rural Engineering
College, Bhalki, Karnataka state.
Dr.Subhash.S.Kulkarni completed BE in Electronics and
Communication Engg in 1988 and Masters program in Electronic
Design & Technology from Indian Institute of Science, Bangalore in
1995.He was awarded PhD from IIT, Kharagpur in 2002 in the area
Geometric Deformable Models for Image Segmentation .Presently he is
working as Principal in Jayaprakash Narayan College of Engineering,
Mahabubnagar, Andhra Pradesh. Till date he has more than 30
publications in International & National journals and Conferences and is
guiding 8 research scholars.
Dr.Arunkumar. Lagashetty completed M.Sc in 2000 and M.Phil in 2001
from Gulbarga University, Gulbarga. He was awarded PhD from
Gulbarga University in 2004 in the area of Physical chemistry .He was a
Junior Research fellow for an UGC Project. Till date he has more than
28 publications in International and National journals and more than 30
publications in conferences. Presently, he is working as a Head of
department of Chemistry at Appa Institute of Engineering and
Technology, Gulbarga, Karnataka state.
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