Electromagnetic studies on nano sized magnesium ferrite


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Electromagnetic studies on nano sized magnesium ferrite

  1. 1. International JournalElectronics and Communication Engineering & Technology (IJECET), ISSNInternational Journal of of Electronics and Communication IJECETEngineering & Technology (IJECET) Volume 2, Issue 2, May-July (2011), © IAEME0976 – 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.comABSTRACTNanosized spinel ferrite MgFe2O4 has been prepared by microwave synthesistechnique.The dielectric properties of this sample are studied in the frequency range1KHz-1MHz and in the temperature range 0-7000 C. The effect of temperature andfrequency on ac conductivity, dielectric constant and dielectric loss have beendiscussed in terms of hopping of charge carriers. Electrical properties of MgFe2O4were 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 lowfrequency region.The dielctric constant decreases with increasing frequency and isfound to follow the Maxwell-Wagner interfacial polarization.Magnetic properties aremeasured using a VSM and the corresponding hysteresis loop is obtained. It isobserved that, Q-factor obtained here is high (150) compared to the Q-factor obtainedin case of bulk ferrites.Keywords: Microwave synthesis,Hysteresis loop,a.c.conductivity,dielectric constant,Q-factor1. INTRODUCTIONMagnesium ferrite (MgFe2O4) is an important magnetic oxide with spinel structure[1]. Magnesium ferrite and allied compounds have found wide spread applications inmicrowave devices because of their low magnetic and dielectric losses, and highresistivites [2]. Synthesis of nano -sized MgFe2O4 is important for its magneticproperties, particularly super paramagnetic behavior and super paramagnetic particlesand these can be used for different biomedical applications [3]. 8
  2. 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEMEMagnesioferrite (MgFe2O4) is a magnetic bi-oxide ceramic material with excellentchemical 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 thephenomena of distribution of Mg2+ ions on the sites depend on the synthesistemperature, directly affecting some magnetic properties, such as saturationmagnetization (MS) and transition temperature, which vary with the conditions of heattreatments[4].2. EXPERIMENTAL PROCEDUREHere, microwave firing is used for synthesis of magnesium ferritematerials.Nanosized MgFe2O4 is synthesized by microwave route using urea as afuel.Magnesium oxalates and iron oxalates were prepared by dissolving magnesiumand iron salt in oxalic acid solution.Then,these two oxalates are irradiated withmicrowaves 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 theformation of spinel structure. Similarly, from the SEM image, the formation of nano-sized magnesium ferrite is confirmed [5].2.1 Preparation of pelletsThe powders were crushed and ground finally to reduce it to small crystallites ofuniform size. Then the powder was pressed into different shapes for the studies. Themixture was dried and a small amount of PVA binder was added to the powder .Theresulting powders were pressed by applying a pressure of 70 Mpa in a stainless steeldie to make pellets of 1cm diameter and 1cm thickness for dielectric measurementsand toroid shaped particles for magnetic measurements. Then some of the pelletswere polished to get a uniform parallel surface. These samples were polished toremove any roughness present on the surfaces. Silver paste was coated on theirsurfaces to enable them to act as good electrical contacts for measuring electrical anddielectric properties. The binder burn off was carried out by a slow heating rate. Thesetoroid shaped pellets were used for VSM (vibrating sample magnetometer) magneticfor measurements.2.2 InstrumentationThe powder X-ray diffraction pattern was obtained from GEOL JDX-8P X-raydiffractometer using Cu-Kα radiation. The morphology of the sample was obtainedfrom Leica Cambridge-440 scanning electron microscopy .Bonding in nickel ferritewas obtained from Perkin-Elmer FTIR spectrophotometer (1000). The magneticcharacterization of toroid shaped pellets was done using Vibrating samplemagnetometer (VSM). A c conductivity measurements and dielectric propertyinvestigation were carried out at room temperature over the different frequency usingKeithely high precision multimeter .The quality factor (Q) was obtained from theLCR-Q precision meter (Model HP-4192A)3. MAGNETIC PROPERTIESTo find saturation magnetization, coercivity, remanance and other related parameters,M-H curves are obtained with Foner vibrating sample magnetometer. The values ofsaturation magnetization, MS, remanance ,Mr, coercivity, HC for MgFe2O4 have beendetermined 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 9
  3. 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME3.1 Hysteresis loop: Fig (1) shows the M-H curve of magnesium ferrite. The area ofthe hysteresis loop corresponds to energy loss per unit volume per cycle.Ferromagnetic materials, which have tall, narrow hysteresis loops with small loopareas, 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 madewith materials that have large coercive field intensities HC and hence fat hysteresisloops. 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 beconsidered as the hard magnetic material. Fig (1) Hysteresis loop of magnesium ferrite4. DIELECTRIC MEASUREMENTSThe dielectric behavior for the present samples can be explained on the basis that themechanism 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 differentfrequencies 1 KHz, 10 KHz, 100 KHz and 1 MHz as shown in fig (2).From fig (2), itis observed that, the ac conductivity decreases with increasing frequencies. A fall in σac is observed at higher frequencies .Similarly, the effect of temperature on the acconductivity of magnesium ferrite were studied in the temperature range 00C-7000C.It was observed that, the ac conductivity increases with the increase of temperatureensuring the semiconducting nature of the sample [7] till reaching a maximum, then,ac conductivity decreases to a minimum. Peaks of ac conductivity were observed toshift towards higher temperature indicating a fall in conductivity. Very lowconductivity 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 εwith increasing frequency. This is a normal dielectric behavior of ferrimagneticmaterials, 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 withincreasing temperature, until reaching a maximum then decreases with furtherincrease in temperature.The dielectric dispersion in ferrites can be explained on the basis of space chargepolarization by the Maxwell-Wagner model. The applied voltage on the sample dropsmainly across the grain boundaries, causing localized accumulation of charge underthe influence of an electric field. The space charge in ferrites comes predominantlyfrom the electron hopping between Fe2+ and Fe3+. In ferrites the solids consist of well- 10
  4. 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEMEconducting grains separated by poorly conducting grain boundaries. The electronsreach the grain boundaries by hopping and if the resistance of the grain boundary ishigh enough, electrons pile up and produce polarization at these places. With anincrease of the frequency of the applied field, the electrons reverse their directionmore often; even the electron exchange between Fe2+ and Fe3 ion pairs cannot followthe change of the external applied field above a certain frequency. These effects resultin a decrease in the probability of electrons reaching the grain boundaries andreducing the polarization of electrons. Therefore, the dielectric constant ε decreaseswith 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 higherfrequencies. It is known that the dielectric constant of ferrites, in general, is dependenton dipolar, interfacial, ionic and electronic polarizations. Dipolar and interfacialpolarizations play important role at lower frequencies and are temperature dependent.At higher frequencies, ionic and electronic polarizations contribute to the dielectricconstant and are temperature independent .Therefore, in the present ferrites, thesignificant increase in dielectric constant at lower frequencies with temperature arisesfrom the dipolar and interfacial polarizations [9].4.3 Dielectric loss [ε´´] εAll dielectric materials have two types of losses .One is the conduction loss,representing the flow of actual charges through the dielectric material. The otherdielectric 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 shownin fig (4).The variation of ε” with different frequencies shows expected dispersionbehavior i.e. it decreases with increasing frequency. The ε” show dispersion in thelow frequency region, which is attributed to domain wall motion. At higherfrequencies, the losses are found to be low if domain wall motion is inhibited andmagnetization is forced to change by rotation .Similarly, the variation of ε” withtemperature also follows the expected trend i.e. in general, ε” increases withincreasing temperature and is explained basis of interfacial and spacepolarization[10]. 11
  5. 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 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 12
  6. 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 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 13
  7. 7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 2, Issue 2, May-July (2011), © IAEME4.4 Q-factor studiesThe 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 isobserved that, Q-factor decreases with the increase of frequency and reaches 50 at afrequency of 1MHz. This behavior agrees with the results reported earlier [11].Thenature of the variation of Q-factor with frequency also agrees with the results obtainedearlier [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 allthese reasons, Q-factor remains high for this sample. But, it is worth noting that, theQ-factor values in the whole frequency range 1KHz-IMHz are high compared to thevalues obtained in the case of nano- ferrites as reported earlier [13].Further, Q-factorvalues reported for this sample are for the pellets that were sintered in microwaveoven for much shorter duration(5mins)than those reported earlier5. CONCLUSIONSThe magnesium ferrite nanoparticles were prepared by using a domestic microwaveoven without any refluxing system .The yield, grain size and other characteristicsobserved indicate that the method followed in the present study can be considered assuitable 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. Highdielectric losses (5×1010) are observed at low frequencies. Loss decreases withincreasing frequencies which is a normal behavior. Q-factor obtained here is in therange of 150.So, this sample may find applications in good quality chip inductors andit 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. 14
  8. 8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 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 properties after sintering”, Intl.Jrl.Material Science and Engineering, B111,pp 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. 15