Structural, dielectric and magnetic properties of Ni substituted zinc ferrite

Structural, dielectric and magnetic properties of Ni substituted zinc ferrite

Journal of Magnetism and Magnetic Materials 363 (2014) 114–120 Contents lists available at ScienceDirect Journal of Magnetism and Magnetic Materials...

880KB Sizes 4 Downloads 326 Views

Journal of Magnetism and Magnetic Materials 363 (2014) 114–120

Contents lists available at ScienceDirect

Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm

Structural, dielectric and magnetic properties of Ni substituted zinc ferrite S.S. Kumbhar a, M.A. Mahadik a, V.S. Mohite a, K.Y. Rajpure a, J.H. Kim b, A.V. Moholkar a, C.H. Bhosale a,n a b

Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, India Department of Materials Science and Engineering, Chonnam National University, 300 Yong bong-Dong, Puk-Gu, Gwangju 500-757, South Korea

art ic l e i nf o

a b s t r a c t

Article history: Received 24 January 2014 Received in revised form 6 March 2014 Available online 16 March 2014

NixZn1  xFe2O4 ferrite has been synthesized by the ceramic method using Ni CO3, ZnO, Fe2O3 precursors. The influence of Ni content on the structural, morphological, electrical and magnetic properties of NixZn1  xFe2O4 ferrites is studied. The X-ray diffraction (XRD) analysis reveals that the samples are polycrystalline with spinel cubic structure. The SEM images of NixZn1  xFe2O4 ferrite show that the grain size decreases with an increase in the Ni content. The tetrahedral and octahedral vibrations in the samples are studied by IR spectra. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell–Wagner type of interfacial polarization. Conduction mechanism due to polarons has been analyzed by measuring the AC conductivity. Impedance spectroscopy is used to study the electrical behavior. Magnetic properties of NixZn1  xFe2O4 are studied by using hysteresis loop measurement. The maximum value of saturation magnetization of 132.8 emu/g obtained for the composition, x¼0.8, is attributed to magnetic moment of Fe3 þ ions. & 2014 Elsevier B.V. All rights reserved.

Keywords: Ni–Zn ferrite X-ray diffraction AC conductivity Impedance spectroscopy

1. Introduction Spinel ferrite materials are extensively studied in the fields of science and technology because of their potential applications [1]. Spinel zinc ferrite (ZnFe2O4) has attracted wide attention due to its interesting magnetic properties and application in the photocatalytic properties [2]. The substituted ferrite materials prepared by different techniques have become more important for both in fundamental and application point of view [3]. The high frequency application becomes possible because of extensive investigations in the substuituted nickel ferrites [4]. The nickel (Ni) substituted zinc ferrite plays an important role in technological applications like telecommunication, power transformers, and microwave devices etc. [5]. These ferrites are magnetically soft materials that possess versatile properties like high saturation magnetization, low coercivity, high resistivity and low dielectric loss [6]. Currently many efforts have been made for the miniaturization, particularly; zinc ferrite particles are being devoted to the study of magnetic ferrites at the nanometer scale [7]. Ferrites are structure sensitive materials and their properties critically depend on the followed manufacturing methods such as, oxalate precipitation method,

flash-combustion method, citrate precursor method [8–11]. Verma et al. studied the structural and morphological properties of (Ni, Zn) Fe2O4 by citrate precursor method and observed that the resistivity of Ni–Zn ferrite is greater than 108 Ω cm [12]. The AC magnetic susceptibility measurements of Ni–Zn-ferrite synthesized by co-precipitation route are carried out by Gul et al. to measure the transition temperature [13]. Sutka et al. prepared nickel zinc ferrite using sol–gel auto combustion method and found that the zinc ion influence on conductivity of the gas sensor material [14]. Misra et al. reported that the increase in the saturation magnetization in zinc ferrite nanoparticles is attributed to the change in the cation distribution from a normal spinel to a mixed spinel structure in the nanocrystalline form [15]. In present investigation, NixZn1  xFe2O4 (x ¼0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ferrites have been prepared by the standard double sintering ceramic method. The purpose of present study is to investigate the effect of Ni content on the morphological, structural and electromagnetic properties of zinc ferrite to improve the materials performance for its various applications.

2. Experimental n

Corresponding author. Tel.: þ 91 231 2609223; fax: þ 91 231 2691533. E-mail address: [email protected] (C.H. Bhosale).

http://dx.doi.org/10.1016/j.jmmm.2014.03.024 0304-8853/& 2014 Elsevier B.V. All rights reserved.

The nickel–zinc ferrite having a general formula NixZn1  xFe2O4 were prepared by the ceramic method (with x ¼0.0, 0.2, 0.4, 0.6,

S.S. Kumbhar et al. / Journal of Magnetism and Magnetic Materials 363 (2014) 114–120

0.8, and 1.0) and by using nickel carbonate, zinc oxide and ferric oxide as starting materials. These starting materials were taken in stoichiometric proportion and milled thoroughly using agate mortar for 3 h. This mixture was presintered at 900 1C for 9 h to decompose the carbonates and oxides. The resultant powder was again ground for half an hour in order to obtain a more homogenous powder. Polyvinyl alcohol was used as a binder. The mixture with 2% polyvinyl alcohol was pressed by using a hydraulic press, giving a pressure of 5 tons for 10 min. These pellets were again sintered at 1000 1C for 10 h to reduce the porosity and increase the density. Finally, silver paste was applied to obtain good ohmic contacts on both sides of the pellets. The structural properties of ferrites were studied by using Philips PW-3710 X-ray diffractometer using Cu-Kα radiation. The surface morphology was studied by using JEOL JSM 6360 scanning electron microscope. The IR spectra were recorded by PerkinElmer spectrometer in the frequency range of 400–4000 cm  1. The dielectric constant (ε0 ), loss tangent (tan δ), and impedance were measured at room temperature in the frequency range 20 Hz to 1 MHz using LCR meter Bridge (model HP 4284A). Magnetic measurements at room temperature for all compositions were studied by using a computerized high field hysteresis loop tracer (Magenta, Mumbai) at a magnetic field strength of 2.5 kOe.

3. Results and discussion 3.1. Structural properties Fig. 1 shows the X-ray diffraction patterns of NixZn1  xFe2O4 obtained with Cu-Kα (1.54056 Ǻ) radiation. The samples are polycrystalline in nature with no impurity peak present. The most intense peak (311) confirms the formation of spinel ferrite [16]. The other planes such as (2 2 0), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) are also observed with smaller intensities. The peaks obtained are indexed by using JCPDS card no. 08-0234. The lattice constant ‘a’ is calculated by using the following formula: a d ¼ pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 2 h þk þl

ð1Þ

(440)

(511)

(422)

(400)

(311)

Intensity (a.u)

(220)

where, (hkl) are miller indices,‘d’ is interplaner spacing and ‘a’ is lattice parameter. The calculated values of lattice parameters show that, as Ni content increases, values of lattice parameter decrease.

This may be due to ionic radius of nickel (ionic radius of Ni¼0.74 Ǻ, Zn¼ 0.83 Ǻ and Fe¼0.65 Ǻ) is less than the ionic radius of the Zn. These results are in good agreements with the results obtained by Kambale et al. [17]. The average crystallite size ‘D’ of NixZn1 xFe2O4 samples was calculated using the Debye–Scherrer formula D¼

0:9λ β cos θ

ð2Þ

where ‘λ’ is the wavelength of X-ray (1.5406 Ǻ), ‘β’ the full-width at half-maximum in radian, and ‘θ’ the angle of diffraction. It is seen that crystallite size (D) varies in between 24 and 33 nm as depicted in Table 1. 3.2. IR-spectroscopy Fig. 2 shows the IR spectrum of Ni0.8 Zn0.2 Fe2O4 ferrite recorded in the wave number range of 400–4000 cm  1 at room temperature. The absorption bands are in the expected range which confirms the formation of spinel structure of ferrite [3]. In ferrites the atoms are bound together to all nearest neighbors by equivalent forces (ionic, covalent or van der waals). According to geometrical configuration of oxygen, the metal ions are situated at tetrahedral (A) site and at octahedral (B) site [18]. From this spectrum it is seen that there are two main metal oxygen bands (υ1, υ2) observed at 637 and 449 cm  1. These bands are the common features of all the ferrites. These bands are attributed to stretching vibrations due to the interaction between the oxygen atoms and the cations in tetrahedral and octahedral positions respectively [19]. These results are in good agreements with the results obtained by Pathak et al. [20]. The most important peaks Table 1 The values for lattice constant (a), crystallite size (D), grain size (t), theoretical density Dx for Ni doped Zn1  xFe2O4. Sr. no.

Ni content (x)

Lattice Crystallite size constant 'a' (Ǻ) (D) (nm)

Grain size (t) Density (Dx) (μm) (g/cm3)

1 2 3 4 5 6

0.0 0.2 0.4 0.6 0.8 1.0

8.43 8.42 8.40 8.35 8.38 8.34

1.74 1.18 0.78 0.54 0.3 0.2

x=1.0

50

x=0.8

40

24.1 27.8 24.9 26.4 24.1 33.3

5.33 5.32 5.33 5.40 5.30 5.35

449.577

x=0.6

836.16

30

%T

x=0.4

115

20

x=0.2 10

3435.450 636.694

x=0.0 2928.476

08-0234

20

30

40

50 60 2θ (degree)

70

80

Fig. 1. X-ray diffraction patterns for NixZn1  xFe2O4 ferrite (x ¼ 0.0–1.0) prepared by ceramic method and presintered at 1000 1C for 10 h.

0 4000

3500

3000

2500

1114.882 1629.853

2000

1500

1000

500

-1

wavenumber (cm ) Fig. 2. IR spectrum of Ni0.8 Zn0.2 Fe2O4 ferrite recorded at room temperature.

116

S.S. Kumbhar et al. / Journal of Magnetism and Magnetic Materials 363 (2014) 114–120

are at 3415 cm  1, 2928 cm  1, 1630 cm  1, 1114 cm  1, and 836 cm  1 corresponding to the OH-stretching and bending vibrations of H2O absorbed by the samples [21]. 3.3. Morphological studies Surface morphological properties of the nickel–zinc Ferrite samples were studied by using scanning electron microscopy (SEM). Fig. 3 shows the scanning electron micrographs of NixZn1 xFe2O4 ferrite (with x¼ 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) samples sintered at 1000 1C for 10 h. The grain size of NixZn1 xFe2O4 ferrite decreases with an increasing Ni content, from 1.7 to 0.2 μm as shown in Fig. 3 indicating the denser samples at high concentrations of nickel. In order to check the concentration of Ni, the density measurement was carried out. The density (Dx) of the NixZn1 xFe2O4 was calculated by using the following formula: Dx ¼

8M Na3

ð3Þ

where ‘M’ is the molecular weight of the ferrite, ‘N’ is the Avogadro's number and ‘a3’ is the volume of the unit cell. It is seen that the density of the samples is maximum for x¼0.6 as shown in Table 1. This might be due to density as it depends on the atomic weight. At x¼0.6 the atomic weight of nickel is greater as compared to zinc.

3.4. Dielectric properties The variation of dielectric constant with frequency for NixZn1  xFe2O4 is shown in Fig. 4(a). It is seen that dielectric constant decreases with an increase in the frequency, indicating the dielectric dispersion in the lower frequency range [22]. This dispersion behavior is due to the Maxwell–Wagner type interfacial polarization in accordance with Koop's phenomenological theory [23]. The space charge polarization due to inhomogeneous dielectric structure explains the high value of dielectric constant observed at lower frequencies [24]. In ferrites, electrons are the main charge carriers and the motion of the electrons takes place

Fig. 3. Scanning electron micrographs of NixZn1  xFe2O4 ferrites, (x ¼ 0.0 to 1.0) prepared by ceramic method and presintered at 1000 1C for 10 h.

S.S. Kumbhar et al. / Journal of Magnetism and Magnetic Materials 363 (2014) 114–120

117

8 x=0.0 x=0.2 x=0.4 x=0.6 x=0.8 x=1.0

16000

12000

6

10000

tan δ

Dielectric Constant (ε')

14000

x=0.0 x=0.2 x=0.4 x=0.6 x=0.8 x=1.0

8000

4

6000 2

4000 2000

0

0 1

2

3

4

5

1

6

2

3

log f

4

5

6

log f

8.8 x=0.0 x=0.2 x=0.4 x=0.6 x=0.8 x=1.0

8.4

log ( σac)

8.0 7.6 7.2 6.8 6.4 4

5

6

7

8

9

10

11

log (ω 2 ) Fig. 4. (a) Variation of dielectric constant with frequency at room temperature for NixZn1xFe2O4 (x¼ 0.0–1.0). (b) Variation of dielectric loss with frequency at room temperature for NixZn1  xFe2O4 for x ¼ 0.0–1.0 (c) Variation of AC conductivity with frequency at room temperature for NixZn1  xFe2O4 (x ¼0.0–1.0).

between Fe2 þ ions and Fe3 þ ions present at crystallographic equivalent sites, i.e. octahedral sites by hopping mechanism of charge transfer. At the higher frequency, the electron hopping cannot follow the electric field fluctuations causing the dielectric constant (ε0 ) that decreases as shown in Fig. 4(a). It is noted that at x ¼0.2, the highest value of the (ε0 ) as shown in Table 2, is due to the fact that the sample has the highest concentration of the Fe2 þ ions. This leads to the increase of charge carriers and hence polarization inside the sample [25]. The effect of polarization is to reduce the field inside the medium. Therefore, the dielectric constant of a substance may decrease substantially as the frequency is increased. Also Raghavender et al. proposed that the effect of grain boundaries is predominant at lower frequencies. The thinner the grain boundary, higher is the dielectric constant value [26]. As the grain boundaries have large resistance, the electrons pile up and produce large space charge polarization [27]. Fig. 4(b) shows the variation of loss tangent (tan δ) with frequency for NixZn1  xFe2O4 sintered at 1000 1C. This figure shows that tan δ decreases with increasing frequency with shoulder behavior for some samples which may be due to the resonance between the hopping frequency of charge carriers and applied frequency. For other samples the shoulder behavior is not observed due to their resonance frequency lies beyond the measurement frequency range [28].

Table 2 The values for Dielectric constant (ε0 ), Loss tangent (tan δ) and saturation magnetization for Ni doped Zn1  xFe2O4. Sr. Ni No. content (x)

Dielectric constant at 1.2 K Hz

Dielectric loss (tan δ) at 1.2 K Hz

Saturation magnetization (emu/g)

1 2 3 4 5 6

873 1101 859 876 676 624

0.474 0.860 1.600 2.652 1.199 0.160

– – 61.6 130.3 132.8 96.6

0.0 0.2 0.4 0.6 0.8 1.0

3.5. AC conductivity To understand the conduction mechanism in the samples, AC conductivity is studied. Fig. 4(c) shows the plot of log(sac) vs. log ω2. From this plot it is observed that conductivity increases with increase in the frequency. As frequency of the applied field increases, hopping of carriers also increases, thereby increasing conductivity [29]. There are two types of polarons, small polarons and large polarons. In the case of small polarons the conductivity increases linearly with an increase in the frequency and in large types of polarons the conductivity decreases with an increase in

118

S.S. Kumbhar et al. / Journal of Magnetism and Magnetic Materials 363 (2014) 114–120

the frequency. The linear nature of graph shows small type of polaron hopping mechanism. 3.6. Impedance measurements Fig. 5 shows the complex impedance spectra of NixZn1  xFe2O4 samples recorded at room temperature in the frequency range of

20 Hz to 1 MHz. The complex impedance plot is obtained after plotting Z″ vs. Z0 . It is well known that impedance spectroscopy is an important method to study the electrical properties of ferrites since impedance of the grains can be separated from other impedance sources, such as impedance of electrodes and grain boundaries. Due to the space charge polarization and orientation polarization in the ferrite materials, the two semicircles are

X=0.2

300

x=0.0

2000

250 200

Z" (KΩ )

Z" (KΩ)

1500

1000

150 100

500 50 0

0 0

1000

2000

3000

4000

0

5000

200

400

Z' (KΩ )

600

800

1000

Z' (KΩ )

200

X=0.4

180

50

X=0.6

160 40

120

Z" (KΩ)

Z" (KΩ )

140

100 80

30

20

60 40

10

20 0

0 0

100

200

300

400

500

0

600

50

Z' (KΩ )

100

150

200

250

Z' (KΩ)

140

X=0.8

x=1.0

12000

120 10000

Z" (KΩ)

Z" (K Ω )

100 80

8000 6000

60 4000 40 2000 20 0

0 0

100

200

300

400

500

600

0

2000 4000 6000 8000 10000 12000 14000 16000 18000

Z' (KΩ) Fig. 5. Complex impedance spectra for NixZn1  xFe2O4, (x ¼ 0.0–1.0).

Z' (KΩ)

Magnetic moment (emu/ gm)

S.S. Kumbhar et al. / Journal of Magnetism and Magnetic Materials 363 (2014) 114–120

B

x=0.0 x=0.2 x=0.4 x=0.6 x=0.8 x=1.0

-8

-6

-4

-2

119

x¼ 0.0 and x¼ 0.2 do not show the magnetic moment therefore these two samples are diamagnetic in nature.

160 140 120 100

4. Conclusions

80 60 40 20 0 -20 -40

0

A

2

4

6

8

Magntic field strength (Oe) x1000 unit

-60 -80 -100 -120 -140 -160 Fig. 6. Room temperature M-H Hysteresis loops for NixZn1  xFe2O4 (x¼ 0.0–1.0).

The nickel–zinc Ferrite having general formula of NixZn1  x Fe2O4 (with x ¼0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) have been prepared by the ceramic method. The XRD patterns show the purity of the phase. There is no impurity phase in the all samples obtained. The peak (311) confirms the formation of spinel ferrite. SEM images show that the grain size decreases as the Ni content increases. From the IR absorption spectrum it is found that two fundamental bands υ1 and υ2 are in the frequency range 400–600 cm  1. The dielectric constant decreases with an increase in frequency showing dielectric dispersion at lower frequency region. The loss tangent (tan δ) graph shows the shoulder behavior due to the presence of resonance frequency. The grain boundary behavior can be studied from the impedance spectroscopy. The saturation magnetization increases with increasing Ni content and has relatively maximum value of 132.8 emu/g at x ¼0.8.

Acknowledgment observed at x ¼0.6 and at x ¼0.8 as shown in Fig. 5. The first semicircle at low frequency represents the resistance of grain boundary. The second one obtained at high-frequency domain corresponds to the resistance of grain or bulk properties. The plot obtained shows only one semi-circular arc (x¼ 0.0, 0.2, and 0.4) corresponding to the conduction due to the grain boundary volume in the low frequency region, which suggests that conduction mechanism takes place predominantly through the grain boundary volume [30]. 3.7. Magnetization measurements Fig. 6 shows the room temperature magnetization (Ms) measurements of NixZn1  xFe2O4 (where x ¼0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) samples. It is observed that the saturation magnetization increases up to 132.8 emu/g at x ¼0.8 as Ni content increases, and there after goes on decreasing. This may be due to magnetic moment of the few Fe3 þ ions on the A-site no longer to align all the magnetic moment on the B-sites antiparallel to themselves, since this is opposed by the negative B–B exchange interaction [31]. These values of magnetization are higher than the values obtained by Fu et al. and Jalaly et al. They found saturation magnetization (Ms) values increases to 52 emu/g [32] and 83.22 emu/g [33]. It is found that ferrite shows super-exchange effect due to the magnetic moments which are opposite for the Fe3 þ ions in tetrahedral and octahedral holes. When Zn2 þ ions occupies tetrahedral holes then the Fe3 þ ions in octahedral holes are couple in two sub-lattices by the super-exchange effect; this gives the zero molecular magnetic moment of ZnFe2O4. When a small amount of Fe2 þ in Fe3O4 is substituted by Zn2 þ then Zn2 þ ions enter tetrahedral holes and force the Fe3 þ ion to move to octahedral holes to increase the ligand field stabilization energy. The Fe3 þ ions remaining in tetrahedral holes have spins opposite to those in octahedral holes due to super-exchange as is found in the inverse spinel Fe3O4. When the amount of Zn2 þ added is small the Fe3 þ ions in octahedral holes increase and that of Fe3 þ in tetrahedral holes decrease. Thus the saturation magnetization increases with the doping amount of Zn2 þ . On the other way when the amount of substituent is large, the super-exchange effect causes the Fe3 þ ions in two sublattices of octahedral holes to have opposite spins and saturation magnetization decreases with doping amount of Zn2 þ [34]. Hence, the first two samples when

One of the aouthors (SSK), is very much thankful to the Department of Physics, Shivaji University Kolhapur for awarding the Departmental Research Fellowship (DRF) and UGC DSA-I, DST FIST-II programmes for the financial support. References [1] M.R. Anantharaman, S. Jagatheesan, K.A. Malini, S. Sindhu, A. Narayanasamy, C.N. Chinnasamy, J.P. Jacobs, S. Reijnen, K. Seshan, R.H.H. Smits, H.H. Brongersma, J. Magn. Magn. Mater. 189 (1998) 83–88. [2] P. Ren, J. Jhang, H. Deng, J. Wuhan Univ. Tech-Mater. Sci. Ed. 24 (2009) 927–930. [3] M.M. Mallapur, P.A. Shaikh, R.C. Kambale, H.V. Jamadar, P.U. Mahamuni, B.K. Chougule, J. Alloys Compd. 479 (2009) 797–802. [4] M. Ishaque, M.U. Islam, M.A. Khan, I.Z. Rahman, A. Genson, S. Hampshire, Physica B 405 (2010) 1532–1540. [5] M. Siva Ram Prasad, B.B.V.S.V. Prasad, B. Rajesh, K.H. Rao, K.V. Ramesh, J. Magn. Magn. Mater. 323 (2011) 2115–2121. [6] P.P. Sarangi, S.R. Vadera, M.K. Patra, N.N. Ghosh, Powder Technol. 203 (2010) 348–353. [7] M. Sivakumar, A. Towata, K. Yasui, T. Tuziuti, Y. Iida, Curr. Appl. Phys. 6 (2006) 591–593. [8] Y.M.Z. Ahmed, Ceram. Int. 36 (2010) 969–977. [9] T.J. Shinde, A.B. Gadkari, P.N. Vasambekar, Mater. Chem. Phys. 111 (2008) 87–91. [10] R.V. Mangalaraja, S. Ananthakumar, P. Manohar, F.D. Gnanam, Mater. Sci. Eng. A 355 (2003) 320–324. [11] E.E. Sileo, R. Rotelo, S.E. Jacob, Physica B 320 (2002) 257–260. [12] A. Verma, T.C. Goel, R.G. Mendiratta, R.G. Gupta, J. Magn. Magn. Mater. 192 (1999) 271–276. [13] I.H. Gul, W. Ahmed, A. Maqsood, J. Magn. Magn. Mater. 320 (2008) 270–275. [14] A. Sutka, G. Mezinskis, A. Lusis, M. Stingaciu, Sens. Actuator B 171 (172) (2012) 354–360. [15] R.D.K. Misra, S. Gubbala, A. Kale, W.F. Egelhoff, Mater. Sci. Eng. B 111 (2004) 164–174. [16] M.B. Shelar, P.A. Jadhav, S.S. Chougule, M.M. Mallapur, B.K. Chougule, J. Alloys Compd. 476 (2009) 760–764. [17] R.C. Kambale, N.R. Adhate, B.K. Chougule, Y.D. Kolekar, J. Alloys Compd. 491 (2010) 372–377. [18] R.C. Kambale, K.M. Song, Y.S. Koo, N. Hur, J. Appl. Phys. 110 (2011) 053910–053917. [19] M.A. Gabal, Y.M. Al Angari, J. Magn. Magn. Mater. 322 (2010) 3159–3165. [20] T.K. Pathak, N.H. Vasoya, V.K. Lakhani, K.B. Modi, Ceram. Int. 36 (2010) 275–281. [21] M.G. Naseri, E.B. Saion, H.A. Ahangar, A.H. Shaari, M. Hashim, J. Nanomater. 2010 (2010) 75. [22] P.A. Jadhav, M.B. Shelar, B.K. Chougule, J. Alloys Compd. 479 (2009) 385–389. [23] R.G. Kharabe, R.S. Devan, C.M. Kanamadi, B.K. Chougule, Smart Mater. Struct. 15 (2006) N36–N39. [24] Y.B. Kamble, S.S. Chougule, B.K. Chougule, J. Alloys Compd. 476 (2009) 733–738.

120

S.S. Kumbhar et al. / Journal of Magnetism and Magnetic Materials 363 (2014) 114–120

[25] S.A. Rahman, Egypt. J. Solids 29 (2006) 131–140. [26] A.T. Raghavender, K.M. Jadhav, Bull. Mater. Sci. 32 (2009) 575–578. [27] N. Singh, A. Agarwal, S. Sanghi, P. Singh, J. Magn. Magn. Mater. 323 (2011) 486–492. [28] A.D. Shaikh, V.L. Mathe, J. Mater. Sci. 43 (2008) 2018–2202. [29] P.P. Hankare, U.B. Sankpal, R.P. Patil, A.V. Jadhav, K.M. Garadkar, B.K. Chougule, J. Magn. Magn. Mater. 323 (2011) 389–393.

[30] [31] [32] [33]

K.M. Batoo, M.S. Ansari, Nanoscale Res. Lett. 7 (2012) 112–126. T.J. Shinde, A.B. Gadkari, P.N. Vasambekar, J. Magn. Magn. Mater. 333 (2013) 155. Y.P. Fu, C.H. Lin, J. Magn. Magn. Mater. 251 (2002) 74–79. M. Jalaly, M.H. Enayati, F. Karimzadeh, P. Kameli, Powder Technol. 193 (2009) 150–153. [34] Y. Liu, Michael G.B. Drew, Y. Liu, J. Magn. Magn. Mater. 323 (2011) 945–953.