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J. Semicond. > 2013, Volume 34 > Issue 9 > 093002

SEMICONDUCTOR MATERIALS

Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite

S. P. Yadav1, S. S. Shinde2, A. A. Kadam3 and K. Y. Rajpure2,

+ Author Affiliations

 Corresponding author: K. Y. Rajpure, Email:rajpure@yahoo.com

DOI: 10.1088/1674-4926/34/9/093002

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Abstract: The Co1-xMnxFe2O4 (0 ≤ x ≤ qslant 0.5) ferrite system is synthesized by using an auto combustion technique using metal nitrates. The influence of Mn substitution on the structural, electrical, impedance and magnetic properties of cobalt ferrite is reported. X-ray diffraction patterns of the prepared samples confirm that the Bragg's peak belongs to a spinel cubic crystal structure. The lattice constant of cobalt ferrite increases with the increase in Mn content. The microstructural study is carried out by using the SEM technique and the average grain size continues to increase with increasing manganese content. AC conductivity analysis suggests that the conduction is due to small polaron hopping. DC electrical resistivity decreases with increasing temperature for a Co1-xMnxFe2O4 system showing semiconducting behavior. The activation energy is found to be higher in the paramagnetic region than the ferromagnetic region. Curie temperature decreases with Mn substitution in the host ferrite system. Dielectric dispersion having Maxwell-Wagner-type interfacial polarization has been observed for cobalt ferrite samples. Magnetic properties have been studied by measuring M-H plots. The saturation and remanent magnetization increases with Mn substitution.

Key words: combustionMn substitutionstructuraldielectricmagnetic

There is an increasing interest in magnetic ferrite materials because of their broad applications in numerous technological fields including ferrofluids, drug delivery and high-density information storage[1]. To meet the requirements for their use in high-density recording media, the particles must not only have suitable saturation magnetization, remanence, coercivity, high blocking temperature but also reduced size and uniform shape. Among other materials, the CoFe2O4 ferrite system has received increased awareness for its potential use in high-density recording media. This is due to its significant properties such as strong anisotropy, high saturation magnetization and coercivity along with good mechanical hardness and chemical stability[2]. Paulsen et al.[3] reported that the Curie temperature and magnetostriction of substituted Co ferrites are tunable by adjusting the suitable substitution level. Such substituted Co ferrites with optimized material properties are used in magneto–mechanical stress sensors. It has been shown that Mn substituted cobalt ferrites are excellent candidates for stress sensors due to a large magnetomechanical effect and high sensitivity to stress. Palamaru et al.[4] reported the preparation and characterization of CoMnxFe2xO4 by the low temperature combustion method. They demonstrated an increase in the saturation magnetization with the increase in Mn content; also thermal treatment induces a decrease in the coercive field. Kim et al.[5] investigated the structural and magnetic properties of Mn substituted cobalt ferrite synthesized by the sol gel method. They found that Co–Mn powder fired at 673 and 723 K had a spinal cubic structure and a mixed nature of paramagnetic and ferromagnetic phases. A Mossbauer spectrum shows that the Fe ions are on both A (tetrahedral) and B (octahedral) sites in ferric high-spin states. Ji et al.[6] studied Ni–Mn–Co ferrite with equal permittivity and permeability of 7–9, as well as a sufficiently low dielectric and magnetic loss tangent less than 0.001 and 0.01 below 200 MHz, respectively.

Various methods have been developed to prepare the CoFe2O4 ferrite system such as sol–gel[5], micro-emulsion with oil in water micelles[7] or reverse micelles[8], aqueous co-precipitation and calcination[9] and combustion[10]. Despite these different routes, the preparation of Co-ferrite systems suitable for high-density recording is still a challenge. Indeed, the nanomaterials often show a superparamagnetic behavior at RT and a very low saturation magnetization. At present enormously magnetostrictive and resistive ferrites are becoming a significant issue for magnetoelectric (ME) composites which illustrate the ME effect. Substitution of different metals such as Zn, Mn, etc is useful to enhance ME sensitivity.

Therefore an effort has been made to synthesize the nanoparticles of a Co1xMnxFe2O4 (0 x 0.5) system by using a resourceful self-propagating combustion route. In this article we report the synthesis of a Co1xMnxFe2O4 (0 x 0.5) system by an efficient self-propagating auto combustion route. At the outset, the objective of the present study is to study the influence of Mn substitution on structural, morphological, electrical, dielectrical and magnetic properties. Also, the thermomagnetic behavior and Curie temperature of the developed system is studied.

The Co1xMnxFe2O4 (0 x 0.5) ferrite system was prepared by the combustion of a redox mixture containing stoichiometric amounts of corresponding metal nitrates and glycin in a Pyrex dish. The equivalence ratio, Φe (O/F) of the redox mixture for the combustion is calculated by using total oxidizing and reducing valencies of the oxidizer (O) and of the fuel (F), which serve as numerical coefficients so that Φe (O/F), becomes unity and the heat released is at its maximum[11]. According to the principles used in propellant chemistry, the oxidizing and reducing valencies of various elements are considered as follows: C = 4, H = 1, O = 2, N = 0, M = 2, 3, etc. Thus, typically for ferrites i.e. M2+Fe2+3O4 the oxidizing valency of a divalent metal nitrate, M(NO3)2 becomes 10; for trivalent Fe(NO3)3, it is 15, which should be balanced by the total valences in the fuel; glycine (H2NCH2COOH), which add up to +9. Hence the stoichiometric composition of the redox mixture, in order to release the maximum energy for the reaction, requires 40 + 9n = 0 or n = 4.44 mol of glycine. A mixture of cobalt nitrate, manganese nitrate and ferric nitrate in stoichiometric molar proportion was melted in a Pyrex dish by heating at 80 . Glycine was added to the melt and the slurry was introduced into a furnace preheated to 400 . After evaporation of the water content, the mixture frothed and ignited to combust with a flame, giving a voluminous and foamy Co1xMnxFe2O4. After formation of as synthesized powder, the pellets were prepared by pressing in a die of 1 cm diameter and 0.1 mm thickness with the help of a hydraulic press by applying a pressure of 5 ton/in to form the pellets using PVA as a binder. The pellets were finally sintered at 400 in the presence of air.

The structural analysis of powders was made by using an X-ray diffractometer (Siemens D5000) using Cu-Kα radiation (λ = 1.5406 Å). The surface morphology was observed using a JEOL JSM-6360 scanning electron microscope (SEM), Japan. The DC resistivity with respect to temperature was measured using a Keithly electrometer-6514. The frequency dependent dielectric permittivity (ε) and loss tangent (tan δ) in the range from 20 Hz to 1 MHz were studied using a precision LCR meter bridge (HP 4284 A). The hysteresis loops were obtained by using high field hysteresis loop tracer (Magneta B–H loop tracer).

Figure 1 shows XRD patterns of Co-ferrite samples deposited at various Mn substitutions (x= 0, 0.1, 0.2, 0.3, 0.4 and 0.5). All the samples are polycrystalline and show a single phase spinel cubic crystal structure. It shows characteristic reflections of a ferrite phase with strongest (311) orientation[12, 13]. The XRD patterns are indexed using JCPDS card Nos. 22-1086 and 74-2403. The X-ray density (ρx) and measured density (ρm) decreases while porosity increases with Mn content. The linear increase in lattice constant with Mn content may be attributed to the replacement of smaller Co2+ (0.78 Å) by the larger Mn2+ (0.83 Å) ions in the Co1xMnxFe2O4 system obeying Vegards's law[14] as shown in Table 1. The average crystallite size is estimated using Scherrer's formula as shown in Table 1. The average crystallite size decreases with Mn content up to 0.3 and then increases.

Figure  1.  XRD patterns of Co-ferrite samples prepared with various Mn content.
Table  1.  Variation of the structural properties of Co-ferrite samples with Mn content.
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Figure 2 shows scanning electron micrographs of the Co1xMnxFe2O4 with x= 0.2, 0.3, and 0.4 respectively. The Mn substitution induces randomly organized agglomerated grains with different shapes and sizes with slight inter-granular pores. It is observed that the average grain size goes on decreasing with increase in Mn content. It shows significant enhancement in crystallinity. Average grain size varies are in the range of 50–100 nm.

Figure  2.  SEM micrographs of Co-ferrite samples prepared at x= 0.2, 0.3 and 0.4.

Figure 3 shows variation of DC electrical resistivity with temperature. It is seen that the electrical resistivity decreases with an increase in the temperature semiconducting nature of samples. This is due to the increase in the thermally activated drift mobility of charge carriers according to the hopping conduction mechanism. The electrical resistivity decreases with Mn substitution up to 0.3 and then increases. It might be due to a large number of Mn ions occupying A-sites and forcing the Fe ions at A-sites to migrate to B-sites. The hopping probabilities between Mn3+ and Mn2+ ions might also become appreciably high at higher Mn concentration[15]. The activation energy has been calculated by using the Arrhenius relation,

ρ=ρ0expΔEkT,

(1)
Figure  3.  Variation of DC electrical resistivity as a function of temperature of Co1xMnxFe2O4 samples prepared at different sintering temperatures.

where ΔE is the activation energy, k the Boltzmann constant and T the absolute temperature. The activation energies are calculated from the slopes of the paramagnetic and ferromagnetic region and presented in Table 2. The change in slope is observed in ferrite samples due to variation in the Curie temperature[16]. It is evident that the lower activation energy in the ferromagnetic region is attributed to the phase transition or impurity phases, while the change in activation energy is attributed to the change in conduction mechanism[17]. We know that from thermodynamics the magnetic transition is a second-order transition and is accompanied by an expansive change in volume[18]. It is observed that the Curie temperature increases from 410 to 510 K as Mn composition increases from x= 0 to 0.5. The observed variations in Curie temperature have been explained on the basis of the super exchange interactions among the tetrahedral and octahedral cations in the spinel lattice. The net magnetic moment of the spinel lattice is the difference between the magnetic moments of the B and A sub-lattices. Hence, it is therefore expected that a greater amount of thermal energy will be required to off-set the influence of exchange interactions[19].

Table  2.  Variation of activation energy with Mn doping concentration for the Co1xMnxFe2O4 system.
DownLoad: CSV  | Show Table

Figure 4 shows the variation of dielectric constant with frequency at room temperature for the prepared Co-ferrite system. From the figure, it is clear that the dielectric constant (ε) decreases abruptly at lower frequencies and remains constant at higher frequencies showing the dispersion behavior of the dielectric constant for lower frequencies. This dielectric dispersion is attributed to Maxwell[20] and Wagner[21] types of interfacial polarization, which is in agreement with Koop's phenomenological theory[22]. The large value of dielectric constant is associated with space charge polarization and an inhomogeneous dielectric structure. These inhomogeneites are impurities, grain structures and pores. The dielectric constant varies with applied frequency due to charge transport relaxation time. In ferrites at low frequency, rotation of Fe2+ Fe3+ dipoles may be visualized as the exchange of electrons between the ions so that the dipoles align themselves in response to the alternating field giving the maximum polarization. The polarization decreases with increase in frequency and reaches a constant value due to the fact that beyond a certain frequency of external field the electron exchange between Fe3+ Fe2+ ions cannot follow the alternating field[23].

Figure  4.  Variation of dielectric constant as a function of frequency of Co-ferrite samples.

The variation of dielectric loss with frequency is shown in Fig. 5. At lower frequencies tan δ is large and it decreases with increasing frequency. The tan δ is the energy dissipation in the dielectric system, which is proportional to the imaginary part of dielectric constant. At higher frequencies the losses are reduced and the dipoles contribute to the polarization[24]. The loss factor curve is attributed to domain wall resonance. At higher frequencies, losses are found to be low if domain wall motion is inhibited and magnetization is forced to change by rotation. It is clear from Figs. 4 & 5 that the dielectric constant and loss tangent decrease with an increase in Mn substitution.

Figure  5.  Variation of dielectric loss with frequency.

To confirm the AC conduction mechanism, the variation of lg σac with lg ω2 is studied (Fig. 6). The plots are observed to be almost linear indicating that the conduction increases with increase in frequency. The linearity of the plots confirm a small polaron mechanism of conduction. It is known that there are two types of polarons viz. small polarons and large polarons. In the small polaron model, the conductivity increases linearly with increase in frequency and in the case of large polarons, the conductivity decreases with an increase in frequency[25]. The slight decrease in conductivity is attributed to conduction by mixed polarons.

Figure  6.  Variation of log (σac) with lgω2 for Co1xMnxFe2O4 samples.

Figure 7 shows the room temperature B–H hysteresis loop for a Co1xMnxFe2O4 system. The variation of coercivity (Hc), saturation magnetization (Ms) and remnant magnetization (Mr) with Mn content is shown in Table 3. It is found that saturation magnetization (Ms) and remnant magnetization (Mr) increase with Mn content up to x= 0.3. The change in the magnetization due to Mn substitution might be due to a difference in the magnetic moment of the substituted ion on the A-site and B-site of the spinel Co-ferrite and a decrement in the magneto-crystalline anisotropy. A maximum magnetization of about 68.94 emu/gm is observed for the x= 0.3 Mn composition and which might be the most suitable constituent phase for magnetoelectric (ME) composites. The coercivity (coercive force) decreases linearly with increasing Mn content from 1591 to 603 Oe. An initial increase in the saturation magnetization of Co1xMnxFe2O4 at lower concentrations of Mn up to x= 0.3, indicates that initially the Mn2+ ions are substituted in the octahedral (B-site) and for higher concentration it occupies the tetrahedral (A-site) of the spinel lattice. The magnetic moment per formula unit in Bohr magneton is calculated using saturation magnetization (emu/gm)[19]. It is seen that magnetic moment increases with Mn content up to x= 0.3 attains maximum value 2.88 μB and then decreases for higher content (Table 3).

Figure  7.  Room temperature B–H hysteresis loops for the Co1xMnxFe2O4 system.
Table  3.  Variation of magnetic properties with respect to Mn content in Co-ferrite system
DownLoad: CSV  | Show Table

Nanoparticles of a Co–Mn ferrite system are successfully synthesized by following the combustion route. The XRD confirms the formation of a face centered cubic crystal structure. The dielectric behavior shows the electronic polarizability at higher frequencies due to space charge polarization. AC conductivity increases with an increase in the frequency due to the hopping mechanism of conduction. The magnetic study confirms that the saturation magnetization of cobalt ferrite increases with Mn content up to x= 0.3 and decreases for higher Mn content. From this, it is concluded that the composition x= 0.3 is the best suitable constituent phase for the magnetoelectric (ME) composite.

Acknowledgement: The authors are very grateful to the UGC-DSA-I, DST-PURSE and DST-FIST-Ⅱ programs for financial support.


[1]
HaÈfelli U, SchuÈtt W, Teller J, et al. Scientific and clinical applications of magnetic carriers. Plenum, New York, 1997
[2]
Valenzuela R. Magnetic ceramics. Cambridge:Cambridge University Press, 1984:212
[3]
Paulsen J A, Lo C C H, Snyder J E, et al. Study of the Curie temperature of cobalt ferrite based composites for stress sensor applications. IEEE Trans Magn, 2003, 39:3316 doi: 10.1109/TMAG.2003.816761
[4]
Palamaru M N, Iordan A R, Aruxandei C D, et al. The synthesis of doped manganese cobalt ferrites by auto combustion technique. J Optoelec Adv Mater, 2008, 10:1853 doi: 10.1007/s11706-012-0167-3
[5]
Kim W C, Yi Y S, Kim C S. Structural and magnetic properties of Co-Mn ferrite prepared by a sol-gel method. J Magn, 2000, 5:111
[6]
Ji J K, Ahn W K, Kum J S, et al. Miniaturized T-DMB antenna with a low-loss Ni-Mn-Co ferrite for mobile handset applications. IEEE Magn Lett, 2010, 1:5000104 doi: 10.1109/LMAG.2009.2038580
[7]
Moumen N, Veillet P, Pileni M P. Controlled preparation of nanosize cobalt ferrite magnetic particles. J Magn Magn Mater, 1995, 149:67 doi: 10.1016/0304-8853(95)00340-1
[8]
Micelles R, Seip C T, Carpenter E E, et al. Magnetic properties of a series of ferrite nanoparticles synthesized. IEEE Trans Magn, 1998, 34:1111 doi: 10.1109/20.706388
[9]
Grigorova M, Blythe H J, Blaskov V, et al. Magnetic properties and Mösbauer spectra of nanosized CoFe2O4 powders. J Magn Magn Mater, 1998, 183:163 doi: 10.1016/S0304-8853(97)01031-7
[10]
Yan C H, Xu Z G, Cheng F X, et al. Nanophased CoFe2O4 prepared by combustion method. Solid State Commun, 1999, 111:287 doi: 10.1016/S0038-1098(99)00119-2
[11]
Prakash A S, Khadar A M A, Patil K C, et al. Hexamethylenete-tramine:a new fuel for solution combustion synthesis of complex metal oxides. J Mater Synth Processing, 2002, 10:135 doi: 10.1023/A:1021986613158
[12]
Bhatu S S, Lakhani V K, Tanna A R, et al. Effect of nickel substitution on structural, infrared and elastic properties of lithium ferrite. Ind J Pure Appl Phys, 2007, 45:596 doi: 10.3103/S1061386214020083
[13]
McQueeney R J, Bishop A R, Yi Y S, et al. Charge localization and phonon spectra in hole-doped La2NiO4. J Phys Cond Matter, 2000, 12:L317 doi: 10.1088/0953-8984/12/21/102
[14]
Vasoya N H, Lakhani V K, Sharma P U, et al. Study on the electrical and dielectric behaviour of Zn-substituted cobalt ferrialuminates. J Phys:Condens Matter, 2006, 18:8063 doi: 10.1088/0953-8984/18/34/017
[15]
Bao J E, Zhou J, Yue Z X, et al. Electrical and magnetic studies of Ba3Co2Fe23-12xMn12xO41 Z-type hexaferrites. Mater Sci Eng B, 2003, 99:98 doi: 10.1016/S0921-5107(02)00428-2
[16]
Ravinder D, Ravikumar B. A study on elastic behavior of rare earth substituted Mn-Zn ferrites. Mater Lett, 2003, 57:4471 doi: 10.1016/S0167-577X(03)00164-2
[17]
Pujar R B, Kulakarni S N, Chougule B K. Compositional, temperature and frequency dependence of initial permeability in Zr4+ substituted Mg-Zn ferrites. Mater Sci Lett, 1996, 15:1605 http://www.ingentaconnect.com/content/klu/jmsl/1997/00000016/00000020/00174652
[18]
Zemansky M W. Heat and thermodynamics. 6th ed. New York:Mc Graw-Hill Book Company, 1981
[19]
Caltun O, Rao G S N, Rao K H, et al. The influence of Mn doping level on magnetostriction coefficient of cobalt ferrite. J Magn Magn Mater, 2006, 316:e618
[20]
Maxwell J C. Electricity and magnetism. London:Oxford University Press, 1993:828
[21]
Wagner K W. Ann Phys, 1913, 40: 817
[22]
Koop C G. On the dispersion of resistivity and dielectric constant of some semiconductors at audio frequencies. Phys Rev B, 1951, 83:121 doi: 10.1103/PhysRev.83.121
[23]
Devan R S, Kolekar Y D, Chougule B K. Effect of cobalt substitution on the properties of nickel-copper ferrite. J Phys:Conden Matter, 2006, 18:9809 doi: 10.1088/0953-8984/18/43/004
[24]
Agrawal D C. Asian J Phys, 1997, 6: 108
[25]
Mahajan R P, Patankar K K, Kothale M B, et al. Conductivity, dielectric behaviour and magnetoelectric effect in copper ferrite-barium titanate composites. Bull Mater Sci, 2000, 23:273 doi: 10.1007/BF02720082
Fig. 1.  XRD patterns of Co-ferrite samples prepared with various Mn content.

Fig. 2.  SEM micrographs of Co-ferrite samples prepared at x= 0.2, 0.3 and 0.4.

Fig. 3.  Variation of DC electrical resistivity as a function of temperature of Co1xMnxFe2O4 samples prepared at different sintering temperatures.

Fig. 4.  Variation of dielectric constant as a function of frequency of Co-ferrite samples.

Fig. 5.  Variation of dielectric loss with frequency.

Fig. 6.  Variation of log (σac) with lgω2 for Co1xMnxFe2O4 samples.

Fig. 7.  Room temperature B–H hysteresis loops for the Co1xMnxFe2O4 system.

Table 1.   Variation of the structural properties of Co-ferrite samples with Mn content.

Table 2.   Variation of activation energy with Mn doping concentration for the Co1xMnxFe2O4 system.

Table 3.   Variation of magnetic properties with respect to Mn content in Co-ferrite system

[1]
HaÈfelli U, SchuÈtt W, Teller J, et al. Scientific and clinical applications of magnetic carriers. Plenum, New York, 1997
[2]
Valenzuela R. Magnetic ceramics. Cambridge:Cambridge University Press, 1984:212
[3]
Paulsen J A, Lo C C H, Snyder J E, et al. Study of the Curie temperature of cobalt ferrite based composites for stress sensor applications. IEEE Trans Magn, 2003, 39:3316 doi: 10.1109/TMAG.2003.816761
[4]
Palamaru M N, Iordan A R, Aruxandei C D, et al. The synthesis of doped manganese cobalt ferrites by auto combustion technique. J Optoelec Adv Mater, 2008, 10:1853 doi: 10.1007/s11706-012-0167-3
[5]
Kim W C, Yi Y S, Kim C S. Structural and magnetic properties of Co-Mn ferrite prepared by a sol-gel method. J Magn, 2000, 5:111
[6]
Ji J K, Ahn W K, Kum J S, et al. Miniaturized T-DMB antenna with a low-loss Ni-Mn-Co ferrite for mobile handset applications. IEEE Magn Lett, 2010, 1:5000104 doi: 10.1109/LMAG.2009.2038580
[7]
Moumen N, Veillet P, Pileni M P. Controlled preparation of nanosize cobalt ferrite magnetic particles. J Magn Magn Mater, 1995, 149:67 doi: 10.1016/0304-8853(95)00340-1
[8]
Micelles R, Seip C T, Carpenter E E, et al. Magnetic properties of a series of ferrite nanoparticles synthesized. IEEE Trans Magn, 1998, 34:1111 doi: 10.1109/20.706388
[9]
Grigorova M, Blythe H J, Blaskov V, et al. Magnetic properties and Mösbauer spectra of nanosized CoFe2O4 powders. J Magn Magn Mater, 1998, 183:163 doi: 10.1016/S0304-8853(97)01031-7
[10]
Yan C H, Xu Z G, Cheng F X, et al. Nanophased CoFe2O4 prepared by combustion method. Solid State Commun, 1999, 111:287 doi: 10.1016/S0038-1098(99)00119-2
[11]
Prakash A S, Khadar A M A, Patil K C, et al. Hexamethylenete-tramine:a new fuel for solution combustion synthesis of complex metal oxides. J Mater Synth Processing, 2002, 10:135 doi: 10.1023/A:1021986613158
[12]
Bhatu S S, Lakhani V K, Tanna A R, et al. Effect of nickel substitution on structural, infrared and elastic properties of lithium ferrite. Ind J Pure Appl Phys, 2007, 45:596 doi: 10.3103/S1061386214020083
[13]
McQueeney R J, Bishop A R, Yi Y S, et al. Charge localization and phonon spectra in hole-doped La2NiO4. J Phys Cond Matter, 2000, 12:L317 doi: 10.1088/0953-8984/12/21/102
[14]
Vasoya N H, Lakhani V K, Sharma P U, et al. Study on the electrical and dielectric behaviour of Zn-substituted cobalt ferrialuminates. J Phys:Condens Matter, 2006, 18:8063 doi: 10.1088/0953-8984/18/34/017
[15]
Bao J E, Zhou J, Yue Z X, et al. Electrical and magnetic studies of Ba3Co2Fe23-12xMn12xO41 Z-type hexaferrites. Mater Sci Eng B, 2003, 99:98 doi: 10.1016/S0921-5107(02)00428-2
[16]
Ravinder D, Ravikumar B. A study on elastic behavior of rare earth substituted Mn-Zn ferrites. Mater Lett, 2003, 57:4471 doi: 10.1016/S0167-577X(03)00164-2
[17]
Pujar R B, Kulakarni S N, Chougule B K. Compositional, temperature and frequency dependence of initial permeability in Zr4+ substituted Mg-Zn ferrites. Mater Sci Lett, 1996, 15:1605 http://www.ingentaconnect.com/content/klu/jmsl/1997/00000016/00000020/00174652
[18]
Zemansky M W. Heat and thermodynamics. 6th ed. New York:Mc Graw-Hill Book Company, 1981
[19]
Caltun O, Rao G S N, Rao K H, et al. The influence of Mn doping level on magnetostriction coefficient of cobalt ferrite. J Magn Magn Mater, 2006, 316:e618
[20]
Maxwell J C. Electricity and magnetism. London:Oxford University Press, 1993:828
[21]
Wagner K W. Ann Phys, 1913, 40: 817
[22]
Koop C G. On the dispersion of resistivity and dielectric constant of some semiconductors at audio frequencies. Phys Rev B, 1951, 83:121 doi: 10.1103/PhysRev.83.121
[23]
Devan R S, Kolekar Y D, Chougule B K. Effect of cobalt substitution on the properties of nickel-copper ferrite. J Phys:Conden Matter, 2006, 18:9809 doi: 10.1088/0953-8984/18/43/004
[24]
Agrawal D C. Asian J Phys, 1997, 6: 108
[25]
Mahajan R P, Patankar K K, Kothale M B, et al. Conductivity, dielectric behaviour and magnetoelectric effect in copper ferrite-barium titanate composites. Bull Mater Sci, 2000, 23:273 doi: 10.1007/BF02720082
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    S. P. Yadav, S. S. Shinde, A. A. Kadam, K. Y. Rajpure. Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite[J]. Journal of Semiconductors, 2013, 34(9): 093002. doi: 10.1088/1674-4926/34/9/093002
    S P Yadav, S S Shinde, A A Kadam, K Y Rajpure. Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite[J]. J. Semicond., 2013, 34(9): 093002. doi:  10.1088/1674-4926/34/9/093002.
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    Received: 28 January 2013 Revised: 27 April 2013 Online: Published: 01 September 2013

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      S. P. Yadav, S. S. Shinde, A. A. Kadam, K. Y. Rajpure. Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite[J]. Journal of Semiconductors, 2013, 34(9): 093002. doi: 10.1088/1674-4926/34/9/093002 ****S P Yadav, S S Shinde, A A Kadam, K Y Rajpure. Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite[J]. J. Semicond., 2013, 34(9): 093002. doi:  10.1088/1674-4926/34/9/093002.
      Citation:
      S. P. Yadav, S. S. Shinde, A. A. Kadam, K. Y. Rajpure. Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite[J]. Journal of Semiconductors, 2013, 34(9): 093002. doi: 10.1088/1674-4926/34/9/093002 ****
      S P Yadav, S S Shinde, A A Kadam, K Y Rajpure. Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite[J]. J. Semicond., 2013, 34(9): 093002. doi:  10.1088/1674-4926/34/9/093002.

      Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite

      DOI: 10.1088/1674-4926/34/9/093002
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      • Corresponding author: K. Y. Rajpure, Email:rajpure@yahoo.com
      • Received Date: 2013-01-28
      • Revised Date: 2013-04-27
      • Published Date: 2013-09-01

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