M

Sa

b

c

a

ARRA

KSMMC

1

ptcmominhtaatfrt[iwNspn

0d

Materials Chemistry and Physics 129 (2011) 1104– 1109

Contents lists available at ScienceDirect

Materials Chemistry and Physics

jo u rn al hom epage : www.elsev ier .com/ locate /matchemphys

icrostructure and magnetic studies of Mg–Ni–Zn–Cu ferrites

.G. Bachhava, R.S. Patil b, P.B. Ahirraoc, A.M. Patil a, D.R. Patil a,∗

Department of Physics, R.C. Patel Arts, Science & Commerce College, Shirpur, Dist. Dhule, Maharashtra, IndiaDepartment of Physics, P.S.G.V.P. Mandal’s Arts, Commerce & Science College, Shahada, Dist. Nandurbar, Maharashtra, IndiaDepartment of Physics, S.V.S. Arts & Science College, Dondaicha, Dist. Dhule, Maharashtra, India

r t i c l e i n f o

rticle history:eceived 2 February 2011eceived in revised form 2 May 2011ccepted 25 May 2011

a b s t r a c t

Soft Mg–Ni–Zn–Cu spinel ferrites having general chemical formula NixMg0.5−xCu0.1Zn0.4Fe2O4 (wherex = 0.1, 0.2, 0.3, 0.4 and 0.5) were prepared by standard double sintering ceramic method. The sampleswere characterized by X-ray diffraction at room temperature. The X-ray diffraction (XRD) study revealed

eywords:oft ferritesagnetic propertiesg–Ni–Zn–Cu ferrites

that lattice parameter decreases with increase in Ni content, resulting in a reduction in lattice strain.The electrical and magnetic properties of the synthesized ferrites have been investigated as a functionof temperature. The variation of initial permeability and AC susceptibility with temperature exhibitsnormal ferrimagnetic behavior. The variation of initial permeability with frequency is studied. The Curietemperature (TC) in the present work was determined from initial permeability and AC susceptibility.The Curie temperature increases with Ni content.

urie temperature

. Introduction

The ferrite materials substituted with different cations pre-ared by different techniques have become important from bothhe fundamental and application points of view [1,2]. The ferritesontaining Mg and Zn exhibit several interesting properties whichake them suitable for computer memory and logic devices, core

f transformers, recording heads, antenna rods, loading coils andicrowave devices. Ni–Zn ferrites have been used for many years

n the electrical and electronic industries. These are the soft mag-etic ceramics that has spinel configurations [3]. Cu–Zn ferritesave been among the ferrites widely used in electronic indus-ry. Recently, multilayer chip LC filters have been developed as

promising electromagnetic interference (EMI) device [4]. Cu–Znnd Ni–Zn–Cu have been reported useful in multilayer chip induc-ors [5–8]. Ni–Zn–Cu ferrites are important as they posses a quiteew interesting characteristics namely low value of coercivity, highesistivity, negligible eddy current loss for high frequency elec-romagnetic wave propagation and a high mechanical hardness9–11]. It is well known that additives play an important role inmproving the magnetic characteristics of ferrites. In the present

ork, the influence of nonmagnetic Mg2+ as substitute for magnetici2+ on the properties of Ni–Zn–Cu ferrites has been investigated by

tudying structural and magnetic properties of these ferrite sam-les. It is further interested to replace magnetic Ni2+ ions by aon-magnetic Mg2+ in Ni–Zn–Cu ferrites to understand the differ-

∗ Corresponding author. Tel.: +91 9922553765; fax: +91 2563 251808.E-mail address: dr.drpatil@gmail.com (D.R. Patil).

254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.matchemphys.2011.05.067

© 2011 Elsevier B.V. All rights reserved.

ence in the properties of the system of ferrites. The results of thestructural and magnetic characterizations of the prepared samplesare reported here.

2. Experimental

In the present investigation, samples of the Mg–Ni–Zn–Cu ferrites having thechemical formula NixMg0.5−xCu0.1Zn0.4Fe2O4 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) wereprepared by the standard double sintering ceramic technique. The starting materialswere high purity oxides of magnesium, nickel, copper, zinc and iron. The reagentpowders were weighed precisely according to their molecular weight. The oxideswere thoroughly mixed in an agate mortar with acetone for 4 h to homogenize themixture prior to the solid state formation. Heat-treated and compacted in the formof pellets and toroids at 8 t in.−2 using hydraulic press. During this preparation, pre-sintering at 700 ◦C for 12 h and powdering of the formed products were followedby final sintering at 1050 ◦C for 24 h in a programmable furnace and slow cooled toroom temperature to yield the final product. The surfaces of all the samples werepolished in order to remove any oxide layer during the process of sintering. Theweight and dimensions of the pellets were measured to determine bulk densities.

The porosity of the samples was calculated by Archimedes weight differencemethod using xylene liquid (density ∼0.863 g cm−3) in which constituents weretotally insoluble. The single phase formation of the ferrites was confirmed by X-ray diffraction patterns obtained using PHILIPS PW-1710 diffractometer with CuK� radiation (� = 1.5418 A). The infrared spectra were obtained using a Perkin-Elmer IR Spectrometer (Model-783) in the range 200–800 cm−1. Scanning electronmicroscopy (SEM) micrographs were taken using a Cambridge Stereo scan (modelS-120) to reveal the microstructure of the ferrites with respect to the grain size, grainboundaries, pores, inclusions and crystal defects. Curie temperature of the sampleswas obtained from the variation of initial permeability, normalized AC susceptibil-ity. The initial permeability measurements were carried out on toroidal samples

(dimensions 1 cm ID, 2 cm OD and 0.3 cm thick) using Aplab 4912, LCR-Q meter asa function of temperature from room temperature to 450 ◦C at a fixed frequencyof 1 kHz. The initial permeability measurements as a function of frequency werecarried out in the frequency range from 1 kHz to 1 MHz using Hewlett Packard LCRmeter (Model 4292A) at room temperature.

istry and Physics 129 (2011) 1104– 1109 1105

3

3

0tpacXlattooiiHpXrdigcRi

dtwoiitS[f

F8�AiodotactariTcNnmiidKi

S.G. Bachhav et al. / Materials Chem

. Results and discussion

.1. Structural characterization

XRD patterns of NixMg0.5−xCu0.1Zn0.4Fe2O4 (where x = 0.1, 0.2,.3, 0.4 and 0.5) are shown in Fig. 1. The peaks were indexed inhe light of the natural spinel structure of MgAl2O3 in which therominent line of the pattern corresponds to the (3 1 1) plane. Asn evident, all the patterns exhibit all major peaks related to spinelrystal structure. The data on lattice parameter, physical density,-ray density, porosity are given in Table 1. The reported values of

attice parameters for zinc, copper, magnesium and nickel ferritesre 8.42, 8.22, 8.37 and 8.34 A. The value of lattice parameter forhe present samples lies in the range of 8.385–8.415 A. The varia-ion of lattice parameter with nickel content is shown in Fig. 2. It isbserved that the lattice parameter decreases with nickel contentbeying Vegard’s law [12]. In ferrites, Ni2+ and Mg2+ are preferredn the octahedral sites of lattice. The ionic radii of Ni2+ and Mg2+

n octahedral sites are 0.069 and 0.072 nm, respectively [13,14].ence it is expected that the lattice parameter of these ferrite sam-les would decrease with increase in Ni content in the spinel. TheRD data was further used to calculate bond lengths RA, RB and siteadii rA, rB. The bond length RA, RB and site radii rA, rB are found toecrease linearly with nickel content. This is attributed to decrease

n the lattice parameter ‘a’ with Ni content. Lavine [15] has sug-ested that there is an inverse relationship between the covalentharacter of a spinel and bond lengths. Since the bond lengths RA,B decrease with the content of Ni, it can be concluded that there is

ncrease of ionic-covalent character of the spinel with Ni content.Physical density does not show any specific trend. The X-ray

ensity increases with increase in Ni content (Table 1) and is higherhan physical density. This is attributed to the existence of the poreshich were formed and developed during the sample preparation

r sintering process. It is revealed that dx increases with increasen x, since the Mg2+ ions are being replaced by the larger mass Ni2+

ons. Increase in X-ray density can also be attributed to the fact thathe atomic mass of Ni (58.69 amu) is higher than Mg (24.30 amu).imilar results are reported by earlier researcher for Ni–Mg ferrite16]. The average crystallite size of samples estimated by Scherrer’sormula is found in the range of 0.569–0.616 �m.

The room temperature IR spectra of all samples are shown inig. 3. The spectra are recorded in the range from 200 cm−1 to00 cm−1. All the samples show two prominent absorption bands1 and �2 in the range of 600 cm−1 and 400 cm−1, respectively.bsorption at �1 is caused by the stretching of tetrahedral metal

on and oxygen bonding, while �2 is caused by the vibrations ofxygen in the direction perpendicular to the axis joining the octahe-ral ion and oxygen. The IR studies of ferrites attribute occurrencef the band �1 around 600 cm−1 to the intrinsic vibrations of theetrahedral complexes corresponding to the highest restoring forcend band �2 around 400 cm−1 to intrinsic vibrations of octahedralomplexes which are bond bending vibrations. In the present sys-em, the higher band �1 is found to lie in the range of 570–585 cm−1

nd the lower band �2 is found to lie in the range of 380–420 cm−1,espectively, indicating the completion of solid state reaction form-ng the spinel structure. The positions of the bands are presented inable 1. The table reveals that the positions of the absorption bandshange slightly from one ferrite to another. The literature values ofiFe2O4 and ZnFe2O4 also reveal a divergence of the same mag-itude among different investigations [17]. This suggests that theethod of preparation, grain size and porosity may be influenc-

ng factors in locating the band positions. The intensity of bands

s found to improve on Ni2+ addition, indicating that the disor-er of the system decreases on doping. The force constants Kt ando were calculated according to Waldron’s method. The result-

ng values are given in Table 1. The force constant Kt lies in the

Fig. 1. XRD pattern of NixMg0.5−xCu0.1Zn0.4Fe2O4 ferrites.

range of 1.41 × 105–2 × 105 dyne cm−1 and Ko lies in the range of5 5 −1

0.82 × 10 –1.21 × 10 dyne cm . The force constant is a second

order derivative of the potential energy with respect to the bondlength, the other independent parameters being kept constant. Thevariation of force constants Kt and Ko with bond length is given in

1106 S.G. Bachhav et al. / Materials Chemistry and Physics 129 (2011) 1104– 1109

Table 1Data on lattice parameter (a), bond lengths (RA, RB), site radii (rA, rB), molecular weight (M), physical density (da), X-ray density (dx), porosity (Po), average grain size (D), thepositions of IR absorption bands (�1, �2), force constants (Kt , Ko), permeability (�i) and Curie temperature (TC).

Composition(x)

a RA RB rA rB M da dx Po (%) D (�m) �1 �2 Kt Ko �i Curie temp TC

Bypermeability

By acsusceptibility

0.1 8.415 1.924 2.047 0.574 0.695 233.782 4.39 4.99 12 0.689 570 445 2.00 1.21 94 236 2400.2 8.406 1.922 2.044 0.572 0.693 227.221 4.42 5.08 13 0.620 585 420 1.83 1.08 105 252 257

8 15 0.617 570 400 1.67 0.98 115 270 2756 19 0.598 585 390 1.61 0.93 95 325 3145 21 0.574 585 380 1.41 0.82 78 355 360

TwaitA

NTsoioTvTgisf

3

pittmbmimmtd

FN

0.3 8.396 1.920 2.042 0.570 0.690 230.660 4.35 5.10.4 8.392 1.919 2.041 0.569 0.689 234.087 4.28 5.20.5 8.385 1.917 2.038 0.567 0.686 237.517 4.22 5.3

able 1. It is observed that the force constant increases continuouslyith increase in bond length. The present values of force constants

re in good agreement with the values reported by Waldron [18]. Anncrease in force constants with bond lengths can thus be attributedo the strong bonding between oxygen ions and the metal ions at

and B-sites.Fig. 4 represents micrographs of all samples of

ixMg0.5−xCu0.1Zn0.4Fe2O4 (where x = 0.1, 0.2, 0.3, 0.4 and 0.5).he micrographs reveal that the grains are well developed in allamples and separated by pores. No exaggerated grain growth isbserved. The segregation of impurity phase was not observedn samples. This indicates that the complete solid solubility isbtained with the substitution of Ni2+ ions in the present samples.he grain size is calculated using line intercept method. Obtainedalues are in good agreement with estimated values using XRD.he values of average gain size obtained from micrographs areiven in Table 1. It is seen that the grain size decreases withncrease in Ni substitution. The same trend in variation of grainize was observed by previous researchers for Ni–Cu and Mg–Nierrites [19,20].

.2. Initial permeability

The compositional variation of initial permeability of theresent samples is given in Table 1 and is graphically represented

n Fig. 5. The initial permeability increases with nickel content upo x = 0.3 and then decreases there after. The contribution of ini-ial permeability comes from spin rotations as well as domain wall

otion [21,22]. The contribution of the later being is considered toe the major one. The dominant contribution to the permeability inultidomain particles comes from domain wall motion only. Since

n the present investigation, it is reasonable to assume that theaximum contribution to permeability comes from domain wall

otion. For samples with nickel content x = 0.3, it can be concluded

hat Ni2+ when present less in lower content allows easy to freeomain wall motion, whereas higher Ni2+ content appears to cause

8.3808.3858.3908.3958.4008.4058.4108.4158.420

0.50.40.30.20.1

Latti

ce p

aram

eter

(o A)

Content of Ni (x)

ig. 2. Variation of lattice parameter with nickel content inixMg0.5−xCu0.1Zn0.4Fe2O4 ferrites.

Fig. 3. IR spectra of NixMg0.5−xCu0.1Zn0.4Fe2O4 ferrites.

S.G. Bachhav et al. / Materials Chemistry and Physics 129 (2011) 1104– 1109 1107

ixMg0

i�

mft

Ff

Fig. 4. SEM micrograph of N

mpedance to domain wall motion and reduction in magnitude ofi.

In order to study the temperature dependence of initial per-eability (�i), the permeability was determined and plotted as a

unction of temperature. The variation of initial permeability withemperature is shown in Fig. 6. Initial permeability rises to the peak

75

85

95

105

115

125

0.50.40.30.20.1

Nickel content (x)

Initi

al p

erm

iabi

lty

ig. 5. Variation of initial permeability with Ni content in NixMg0.5−xCu0.1Zn0.4Fe2O4

errites.

.5−xCu0.1Zn0.4Fe2O4 ferrites.

value near Curie temperature, giving sharp drops at Curie tem-perature (TC). The sharp drops of �i near TC indicate single phaseformation of the compounds [23]. The peaks in �i–T curves observenear the Curie temperature are due to zero crossing of magneto-crystalline anisotropy constant. The Bloch-walls becomes thick, the

spacing of spores is reduced and initial permeability increases toextreme high levels [24]. Fig. 7 shows the variation of permeabilitywith frequency in different compositions. The values of perme-

0

20

40

60

80

100

120

140

160

400350300250200150100500

Initi

al P

erm

eabi

lity

Temperature (0 C)

x=0.1

x=0.2

x=0.3

x=0.4

x=0.5

Fig. 6. Variation of initial permeability with temperature inNixMg0.5−xCu0.1Zn0.4Fe2O4 ferrites.

1108 S.G. Bachhav et al. / Materials Chemistry and Physics 129 (2011) 1104– 1109

70

80

90

100

110

120

130

65.554.543.53

Initi

al P

erm

eabi

lity

Log F

x=0.1

x=0.2

x=0.3

x=0.4

x=0.5

Ff

adsicsbi

3

N0sCAcTCftamntte

ic

Ff

0

0.2

0.4

0.6

0.8

1

1.2

400350300250200150100500

Temperature (0C)

A.C

. Sus

cept

ibili

ty

x=0.1x=0.2x=0.3x=0.4x=0.5

ig. 7. Frequency dependency of initial permeability in NixMg0.5−xCu0.1Zn0.4Fe2O4

errites.

bility were stable in the frequency range of 1 kHz to 1 MHz andispersion occurs after that. The absence of resonance peak in theseamples shows the materials utility in the frequency range stud-ed. The Curie temperature shows an increasing trend with nickelontent (Fig. 8). The Curie temperature mainly depends upon thetrength of A–B interaction. When nonmagnetic Mg2+ is replacedy Ni2+, there is increased A–B interaction. This leads to the increase

n Curie temperature.

.3. AC susceptibility

The variation of normalized AC susceptibility of theixMg0.5−xCu0.1Zn0.4Fe2O4 ferrite system with x = 0.1, 0.2, 0.3,.4 and 0.5 as a function of temperature is shown in Fig. 9. Allamples show a very small variation in AC susceptibility up tourie temperature. The temperature invariance of normalizedC susceptibility up to Curie temperature suggests that theseompositions contain multidomain particles in predominance.he curves are almost flat and �AC drops off sharply to zero nearurie temperature (TC). The sharp fall at TC shows the single phaseormation of ferrites [23]. The Curie temperatures measured fromhis experiment lie in the range of 240–360 ◦C. This is in closegreement with Curie temperatures obtained from permeabilityeasurements. Curie temperature shows an increasing trend with

ickel content. Double TC behavior is not detected suggesting thathere is no impurity phases present within the material. It supportshe results obtained from SEM. Also, �AC–T tails have not been

xhibited by any of the samples.

The Curie temperatures are presented in Table 1. From the tablet can be seen that the Curie temperature increases with nickelontent. The Curie temperature is nothing but the measure of rel-

200

250

300

350

400

0.50.40.30.20.1

Nickel content (x)

Tc (0 C

)

ig. 8. Curie temperature as a function of Ni content in NixMg0.5−xCu0.1Zn0.4Fe2O4

errites.

Fig. 9. Variation of normalized AC susceptibility with temperature inNixMg0.5−xCu0.1Zn0.4Fe2O4 ferrites.

atively weighted magnetic interaction per formula unit. Strongerthe magnetic interaction larger will be the Curie temperature. Thesubstitution of Ni2+ for Mg2+ should increase the strength of A–Binteraction which consequently requires more thermal energy tooffset the spin alignment and TC increases. These results are in goodagreement with previous studies [16,25].

4. Conclusion

XRD analysis showed all the major peaks related to spinelstructure with increasing Ni content lead to increase the latticeparameters, X-ray density as well as porosity. The IR spectra atroom temperature show two prominent absorption bands �1 and�2 in the frequency the range 600–400 cm−1, respectively, corre-sponding to tetrahedral and octahedral complexes, respectively.A significant increase in initial permeability of ferrite was foundat x = 0.3 of nickel content. Initial permeability remains constantwith temperature and drops to zero at a certain temperature. Thesharp decrease of �i near TC indicates single phase formation ofthe compounds. It is observed that there is no change in �i withfrequency in the range of 1 kHz to 1 MHz. The Curie temperatureshows an increasing trend with nickel content. The temperatureinvariance of normalized AC susceptibility up to Curie temperaturesuggests that these compositions contain multidomain particles inpredominance. Values of Curie temperature determined by initialpermeability and AC susceptibility are in good agreement with eachothers.

Acknowledgements

The authors are thankful to Dr. B.K. Chougule, Material ScienceLaboratory, Shivaji University, Kolhapur, for helpful discussion,guidance and encouragement. One of the authors D.R. Patil is thank-ful to UGC, New Delhi for providing financial assistance underUGC-FIP scheme.

References

[1] H.J. Ritcher, J. Appl. Phys. 32 (1999) R147.[2] H. Gleiter, J. Weissmuller, O. Wollersheim, R. Wurschum, Acta Mater. 49 (2001)

737.[3] J.M. Daneils, A. Rosenewaig, Can. J. Phys. 48 (1970) 381.[4] H.M. Sung, C.J. Chen, w.s.Ko. Wang, IEEE Trans. Magn. 34 (1998) 1363–1365.[5] A. Nakano, S. Saito, T. Nomura, US Patent 5,476,728 (1995).[6] K. Tsuzuki, Eur Patent 1,739,695 (2007).[7] T.T. Ahmed, I.Z. Rahman, M.A. Rahman, J. Mater. Prod. Technol. 153/154 (2004)

797–803.[8] B.P. Rao, K.H. Rao, T.V. Rao, A. Paduraru, O.F. Caltun, J. Opt. Adv. Mater. 7 (2005)

704–710.[9] R.V. Mangalaraj, S. Ananthakumar, P. Manoihar, F.D. Gnanam, J. Magn. Magn.

Mater. 253 (2002) 56.

istry a

[

[

[[

[[[

[

[[[[21] A. Globus, P. Duplex, M. Guyot, IEEE Trans. Magn. (USA) 7 (1971) 617.

S.G. Bachhav et al. / Materials Chem

10] H. Montiel, G. Alvarez, M.P. Gutierrez, R. Zamorano, R. Valenzuela, J. AlloysCompd. 369 (2004) 141.

11] G.L. Sun, J.B. Li, J.J. Sun, Xiao Zhan Yang, J. Magn. Magn. Mater 281 (1–2) (2004)173–177.

12] K.J. Standley, Magnetic Oxide Materials, Clarendon Press, Oxford, 1962.13] V.K. Mittal, S. Bera, R. nithya, M.P. Srinivasan, S. Velmurugan, S.V. Narasimhan,

J. Nucl. Mater. 335 (2004) 302–310.14] R.D. Shannon, Acta Crystallogr. A 32 (1976) 751.15] B.F. Lavine, Phys. Rev. (USA) B7 (1973) 2591.16] M. Naeem, N.A. Shah, I.H. Gul, A. Maqsood, J. All. Compd 487 (1–2) (2009)

739–743.

[[[[

nd Physics 129 (2011) 1104– 1109 1109

17] V.R.K. Murthy, S. Chitrasonkar, K.V. Reddy, J. Sobhanadri, Indian J. Pure Appl.Phys. 16 (1978) 79.

18] R.D. Waldron, Phys. Rev. 99 (1955) 1727.19] X. Tan, G. Li, Y. Zhao, C. Hu, Mater. Res. Bull 44 (2009) 2160–2168.20] V.K. Mittal, S. Bera, R. Nithya, M.P. Srinivasan, J. Nucl. Mater. 251 (2002) 292.

22] A. Globus, M. Guyot, Phys. Status Solidi B 52 (1972) 427.23] S.S. Bellad, S.C. Watwe, B.K. Chougule, J. Magn. Magn. Mater. 195 (1999) 57.24] E. Roses, Ferrites Proc. IFC-3, Kyoto, Jpn, 1970, p. 203.25] M. Kaiser, S.S. Ata-Allah, Mater. Res. Bull. 44 (2009) 1249–1255.