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Magnetic interactions and dielectric behaviour of cobalt ferrite and barium titanate multiferroics nanocomposites
Applied Surface Science 494 (2019) 51–56
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Full length article
Magnetic interactions and dielectric behaviour of cobalt ferrite and barium titanate multiferroics nanocomposites ⁎
T
⁎
S. Mahalakshmia, , R. Jayasria, S. Nithiyanathamb, , S. Swethaa, K. Santhic a
Department of Physics, Ethiraj college for Women(Autonomous), Chennai 600008, India PG and Research Department of physics, Thiru Vi Ka Government Arts and Science College, Thiruvarur 610003, India c Department of Physics and Nanotechnology, SRM University, Kattankulathur, Chennai 603 609, India b
A R T I C LE I N FO
A B S T R A C T
Keywords: Dielectrics Magnetic Titanate Ferrite Nanophase
Multiferroics materials have been used widely in various fields such as ceramic supercapacitors, active and multifunctional devices due to their high relative permittivity with magnetic and ferroelectric behavior even at room temperature. The composites of cobalt ferrite, barium titanate have been synthesized through co precipitation technique and sintered at very high temperature1273K. The existence of titanate single phase and cobalt ferrite structural analysis carried out through ‘X’ Ray diffraction analysis. From the AC analysis the role of phase, dielectric constant, loss tangent and conductivity was also studied. AC conductivity variation was very low at lower frequencies and increases with frequency. Magnetization measurements were carried out at room temperature shows soft ferromagnetic property is 2.8089 emu/g.
1. Introduction
2. Materials and methods
Cobalt ferrite is a class of ferrite possesses the properties such as magnetostrictive, stable, anisotropic and etc. The material with high permittivity with low power loses are suitable for ferroelectric material of Barium titinate [1,2]. The necessary and the required magnetic and electric coupling behavior can be adjusted with proper tuning of volume ratio by changing the phases between the cobalt ferrite and barium titanate [3–6]. The individual component not exhibiting active properties for the lack of phases while the suitable combination of constituents gives rise to magnetoelectric behavior by suitable phases [7,8]. The composites which are separated in physical sense such as magnetic and electric properties [9]. Magnetoelectric materials which exhibit larger phase coupling among the constituents at room temperature [9]. The physical properties varied by strain through compression, charge carrier by exchanging of ions and exchange of spin are improved in magnetoelective effect and inducing the magnetization by polarization [10]. The multiferroic composites are essential for the fabrication of active devices with more range of frequencies region [11]. Moreover, the single phase multiferroic systems are rare in nature which leads to the preparation of ferromagnetic-ferroelectric composite materials [12,13].
Cobalt ferrite powder was prepared by co-precipitation method. The starting materials are Fe(NO3)3∙9H2O and CO(NO3)3∙6H2O. The metal nitrates were taken in stiochiometric ratio of 1:2 and then dissolved in double distilled water and added with aqueous citric acid solution. The metal nitrates and citric acid were taken in the ratio of 1:1. Then the solution was kept in the magnetic stirrer for 4 h. The NH4OH was added drop by drop to maintainpH7 and constant temperature 353 K throughout the stirring process. After 4 h brown coloured precipitate were obtained. The obtained precipitates were kept in the oven for 20 mins. After self-ignition takes places and the fine powder were obtained. Then the colour of the precipitate turned to black. The particles were sintered at 1273 K for an hour. The obtained powder samples were mixed by using Pestle and Mortar then the nano sized Cobalt ferrite was obtained. BaTiO3 nanoparticles were prepared by the following procedure. The precursors used in this reaction were bariumnitrate and titaniumtetra isoperoxide and ethyleneglycol were taken in the ratio 1:1:2. The mixture was dissolved in minimum amount of deionized water followed by nitric acid in order to have a complete reaction of the powder precursors. The obtained solution was stirred in a magnetic stirrer for 4 h with a constant temperature of 353 K. To maintain the pH 7 ammonium hydroxide was then added drop wise. The solution later turned into a pale whitish precipitate. The precipitate was
⁎
Corresponding authors. E-mail addresses: [email protected] (S. Mahalakshmi), s_nithu59@rediffmail.com (S. Nithiyanatham).
https://doi.org/10.1016/j.apsusc.2019.07.096 Received 20 March 2019; Received in revised form 10 June 2019; Accepted 13 July 2019 Available online 17 July 2019 0169-4332/ © 2019 Published by Elsevier B.V.
Applied Surface Science 494 (2019) 51–56
S. Mahalakshmi, et al.
Fig. 1. IR spectra of cobalt ferrite.
Fig. 2. IR spectra of cobalt ferrite, Barium titanate.
grinded using a mortar and pestle to obtain the uniform distribution of the particles. The obtained powder were sintered 1273 K for 3 h, after sintering the powder it was slowly cooled to room temperature.
Table 1 Characteristic FTIR absorption bands. Functional groups
Vibration mode
Fe-OH/Co-OH OH, C-O C-H MO
Valence vibration Stretching modes stretching stretching Intrinsic valance vibration
Wave number (cm−1) 3433 3402 1080 1643 597
3. Result and discussion 3.1. Spectroscopic analysis Fig. 1 shows the FTIR spectra of cobalt ferrite and it observed that the intense absorption band at 3433 cm−1is corresponds to the valence vibrations of metal hydroxyl (FeeOH and CoeOH) [13]. The presence of the peaks in the range 2000–3000 cm−1 is confirming that the presence of OeH, CeO and CeH stretching modes of vibrations [14]. The broad metal‑oxygen bands are known to be observed in
collected and kept in a heating mantle for an hour to obtain dry powder. The dried particles were sintered at 1000Kfor an hour to obtain perovskite BaTiO3 structure. CoFe2O4 and BaTiO3 were taken in equal ratio were manually 52
Applied Surface Science 494 (2019) 51–56
S. Mahalakshmi, et al.
Cobalt ferrite, Barium titanate
0.8 0.6
cobalt ferrite
M o m e n t (e m u )
0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -15000
-10000
-5000
0
5000
10000
15000
Field (G) Fig. 3. Magnetization curve of cobalt ferrite and cobalt ferrite - Barium titanate.
cubic symmetry of TieO stretching vibration is depicted from the absorption of 596 cm−1. In addition to TieO bonding vibration and TiO6 octahedral bonding [16].
Table 2 Magnetic properties of CoFe2O4 and CoFe2O4-BaTiO3.
CoFe2O4-BaTiO3 CoFe2O4
MS (emu/g)
HC (G)
Mr(emu/g)
44 85
191.55 40.27
7.35 3.81
3.2. Magnetic measurements The magnetisation of sample is measured using LAKESHORE 7410 at room temperature 301 K. The measurement carried out at ordinary envrionment of ranges from −15 to +15 Koe− are magnetically ordered are shown in Fig. 3. The antiparallel spins among the Fe3+ ions in tetrahedral sites, Co2+ ions at octaheral sites of CoFe2O4 are reflected from the loop. The Ms was 85 emu/g for CoFe2O4. The magnetization of CoFe2O4 and BaTiO3 decreases due to the introduction of non-magnetic phase which may reduce the magnetic moment and magnetization [17]. The coercivity HC(Oe) increased with the addition
frequencyυ1observed at 597 cm−1 is corresponding to the intrinsic valence vibrations in tetrahedral positions of Mtetra-O in CoFe2O4 [15]. The FTIR spectra of copper ferrite and barium titanate powders are shown in Fig. 2, the peak observed at 596 cm−1 is indicating the stretching vibrations of M-O band. There is no absorption around 1000 cm−1 is confirming that the non-existence of nitrate ions in the prepared samples (Table 1). It is well known that the barium nitrate has
311
700
Cobalt ferrite
600
400
611 222
200
220
300
111
Intensity
500
511
Sample
100
0 0
20
40
60
2theta(degree) Fig. 4. XRD of cobalt ferrite. 53
80
100
Applied Surface Science 494 (2019) 51–56
S. Mahalakshmi, et al.
3.4. Dielectric studies The dielectric studies of cobalt ferrite nanoparticle are measured using the 50LCRHightester (model no: H10KI3532). The plot of relative permittivity vs frequency of pure composite ofCoFe2O4, BaTiO3, CoFe2O4 - BaTiO3 is shown in Fig. 5. From these Figs, it can be observed that the dielectric constant and loss tangent values decreases largely at lower frequency and gradually maintain the constant values are higher frequencies. The charge transport phenomenon is fully depends on the relaxation time, dielectric constant depends on the frequency. The dielectric dissipation occurring at lower frequency ranges indicating the interfacial polarization otherwise Maxwell Wagren type [18,19] for all prepared samples based on Koop's phenomenological theory [20]. The dissipation of energy at lower frequencies is due to all types of polarization mechanism taking place. At high frequencies the occurrence of space charge polarization exhibiting due to inhomogeneous dielectric structure of grain size, impurities and etc. are confirmed through higher dielectric constant [21]. The larger dielectric constant in ferroelectric due to the surface area is covered by ferrite ions [22]. In addition the interface between ferrite and ferroelectric phases possess different concavity and permittivity values are depicted in Fig. 6. The accumulation of charges on the nonconducting interface gives rise to the interfacial polarization in the composites under influence of electric field. At high frequency range the dielectric constant not coherent and this type of works are reported by many researchers [23–25]. The dissipation of energy by means of heat is called dielectric loss. This may reduce the polarization because of grain size, impurities and compactness due to imperfection. Fig. 7 shows the plot of dielectric loss vs frequency and it can be observed that the losses decreased with increasing frequencies and this may be due to the conduction increases is not favor to lagging polarization through mobile ions, electrons and etc. The accumulation of more charges on the interface were improved with conductivity are observed in Fig. 8. The more accumulation due to polarization at the interface is large with electrical conductivity [26].
Fig. 5. XRD of Barium titanate.
of barium titanate in obtained multiferroic material. The same trend is observed in Mr values also (Table 2).
3.3. Structural studies The XRD of cobalt ferrite nanoparticles and barium titanate were measured using X pert pro diffractometer at room temperature. X-ray diffraction patterns of prepared CoFe2O4 and BaTiO3 as shown in Figs. 4 & 5. The XRD patterns confirm the formation of ferrite structure. X-ray diffraction shows the nature of the material with perfect orientation along the (1 1 1), (2 0 2), (2 2 2), (4 0 0), (3 0 2), (3 2 2), (3 1 1) and (3 3 3) planes (JCPDS File no. 96-591-0064 and ferroelectric phase has perovskite tetragonal structure by JCPDS files No. 05-0626). Using the Scherer equation, the particles size of the crystals in the form of powder is determined of about 25 nm. And these XRD patterns reveals that the cobalt ferrite and barium titanate are shown the predominant phases. From this is it confirmed that the first one is cubic spinel structure and later one is perovskite structure.
4. Conclusions Multifferoiccomposites of CoFe2O4 and BaTiO3were synthesized by co-precipitation method. The FTIR spectra of synthesized powders the Fig. 6. Dielectric constant of cobalt ferrite (■), barium titanate ( ) and cobalt ferrite + barium titanate ( ).
2.0
Cobalt ferrite Barium Titanate Cobalt Ferrite, Barium Titanate
1.8 1.6
Dielectric constant
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 1
2
3
4
5
6
7
LogF (Hz) 54
Applied Surface Science 494 (2019) 51–56
S. Mahalakshmi, et al.
Fig. 7. Dielectric loss of cobalt ferrite (■), barium titanate ( ) and cobalt ferrite + barium titanate ( ).
3.0
Cobalt ferrite Barium titanate cobalt ferrite, Barium Titanate
2.5
Dielectric loss
2.0
1.5
1.0
0.5
0.0
1
2
3
4
5
6
7
LogF(Hz)
Fig. 8. Conductivity of cobalt ferrite (■), barium titanate ( ) and cobalt ferrite + barium titanate ( ).
Conductance (Siemens)
0.00020
CoFe2O4 BaTiO3 CoFe2O4- BaTiO3
0.00015
0.00010
0.00005
0.00000
1
2
3
4
5
6
7
LogF (Hz)
peak observed at 596 cm−1, confirmed the stretching vibrations in (TieO) band. Magnetization is less in cobalt ferrite composite rather than pure one. The coercivity increases with the addition of non-magnetic phase barium titanate may reduce the magnetic moment. Dielectric loss develops a lagging behaviour of polarization due to the grain boundaries, imperfection in the crystal lattice and etc., Dielectric loss shown reverse trend with frequency is good for storage and active purpose.
References [1] W. Kleemann, C. Binek, Multiferroic and magnetoelectric materials, Nature 7104 (2013) 759–765. [2] V.S. Puli, A. Kumar, D.B. Chrisey, M. Tomozawa, J.F. Scott, R.S. Katiyar, Bariumzirconate-titanate/barium calcium–titanate ceramics via sol-gel process: novel high-energy-density capacitors. J. Phys. D. Appl. Phys., 44 (2011), pp. 395403–395412 [3] C. SchmitzAntoniak, S. Salamon, H. Trivedi, Y.L. Gao, A. Nazrabi, J. Landers, D. Gautam, M. Winterer, D. Schmitz, H. Wende, V.V. Shvartsman, D.C. Lupascu, Magnetoelectric coupling on multiferroic cobalt ferrite-barium titanate ceramic composites with different connectivity schemes ActaMater., 90 (2015), pp. 1–9. [4] M.H. Frey, D.A. Payne, Grain-size effect on structure and phase transformations for barium titanate Phys, Rev. B 54 (1996) 3158–3316. [5] K. Maaz, A. Mumtaz, S.K. Hasanain, A. Ceylan, Synthesis and magnetic properties of cobalt ferrite (CoFe2O4) nanoparticles prepared by wet chemical route, J. Magn. Magn. Mater. 308 (2007) 289–295. [6] D. Ghosh, H. Han, J.C. Nino, G. Subhash, J.L. JonesSynthesis of BaTiO3-20wt%
Acknowledgement The authors grateful to acknowledge The Management, Ethiraj College for Women, Chennai, provided the necessary facility to complete this work. 55
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[7] [8] [9]
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[11]
[12] [13] [14]
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Mater.Sci. 39 (6) (2016) 1593–1601. [17] S.N. Babu, S.V. Suryanarayana, T. Bhimasankaram, Magnetic and magnetoelectric characterization of Ni0.93Co0.02Mn0.05Fe1.95O4 and PZT composites, J. Alloy Compd. 473 (1–2) (2009) 418–422. [18] J.C. Maxwell, Electricity and Magnetism, 2, Oxford University Press, New York, 1973, p. 828. [19] K.W. Wagner, Study of the dielectric behaviour of Cr-doped zinc Nano ferrites synthesized by sol-gel method, Ann. Phys. 40 (1973) 817–819. [20] C.G. Koops, On the dispersion of resistivity and dielectric constant of some semiconductors at audiofrequencies, Phy.Rev. 83 (1951) 121. [21] D. El Kony, Dielectric relaxation in AL-substituted Ni–Cd spinel ferrites, Egypt. J. Solids 27 (2) (2004) 285–298. [22] Zhi-Cheng Li, Hong Zhang, Xiaodong Zou, Bill Bergman, Synthesis of SmdopedBaTiO3 ceramics and characterization of a secondary phase, Mater. Sci. Engg. B. 116 (2005) 34–39. [23] V.L. Mathe, K.K. Patankar, U.V. Jadhav, A.N. Patil, S.D. Lotake, S.A. Patil, Studies on structural, dielectric and magnetoelectric properties in CuFe1.8Cr0.2O4– Pb(Mg1/ 3V2/3)O3composites, Ceram. Int. 27 (2001) 531–535. [24] K.K. Patankar, V.L. Mathe, A.N. Patil, S.A. Patil, S.D. Lotake, Y.D. Kolekar, P.B. Joshi, Electrical conduction and magnetoelectric effect in CuFe1.8Cr0.2O4–Ba0.8Pb0.2TiO3 composites, J. Electroceram. 6 (2) (2001) 115–122. [25] C.M. Kanamadi, B.K. Chougule, Studies on electrical properties and magnetoelectric effect of (x)Ni0.8Cu0.2Fe2O4 + (1−x)Ba0.8Pb0.2Ti0.8Zr0.2O3 composites, J. Electroceram. 15 (2005) 123–128. [26] M. Yu, Y. Xu, Q. Mao, F. Li, C. Wang, Electromagnetic and absorption properties of nano-sized and micro-sized Fe4N particles, J. Alloys Compd. 656 (2016) 362–367.
CoFe2O4 nanocomposites via spark plasma sintering.J. Am. Ceram. Soc., 95 (2012), pp. 2504–2509. Ce-Wen Nan, Phys. Rev. B50 (1994) 6082. J. Boomgaard, Van Den, R.A.J. Born, A sintered magnetoelectric composite material BaTiO3-Ni(Co, Mn) Fe2O4, J. Mater. Sci. 13 (1978) 1538. C.W. Nan, M.I. Bichurin, S. Dong, D. Viehland, G. Srinivasan, MultiferroicMagnetoelectric composites: historical perspective, status, and future directions, J. Appl. Phys. 103 (2008) 031101. L. Mitoseriu, V. Buscaglia, M. Viviani, M.T. Buscaglia, I. Pallecchi, C. Harnagea, A. Testino, V. Trefiletti, P. Nanni, A.S. Siri, BaTiO3–Ni0.5Zn0.5Fe2O4 ceramic composites with ferroelectric and magnetic properties, J. Eur. Ceram. Soc. 27 (2007) 4379–4382. S.A. Lokare, D.R. Patil, R.S. Devan, S.S. Chougule, Y.D. Kolekar, B.K. Chougule, Electrical conduction, dielectric behavior and magnetoelectric effect in (x)BaTiO3 C (1-x) Ni0.94Co0.01Mn0.05Fe2O4 ME composites, Mater. Res. Bull. 43 (2008) 326–332. N.A. Hill, Why are there so few magnetic ferroelectrics, J. Phys. Chem. B 104 (2000) 6694–6709. V.A.M. Brabers, Infrared spectra of cubic and tetragonal manganese ferrites, Phys. Status Solidi 33 (2) (1969) 563–572. Y.J. Kwon, K.H. Kim, C.S. Lim, K.B. Shim, Characterization of ZnOnanopowders synthesized by the polymerized complex method via an organochemical route, J. Ceram. Process. Res. 3 (3) (2002) 146–149. T. Dippong, E.A. Levei, G. Borodi, F. Goga, L.B. Tudoran, Influence of Co/Fe ratio on the oxide phases in nanoparticles of CoxFe3−xO4, J. Therm. Anal.Calorim. 119 (2015) 1001–1009. T. Ramesh, S.R. Murthy, Electromagnetic properties of nanocrystalline Al3+ substituted MgCuMn ferrites synthesized by microwave hydrothermal method, Bull.
56
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Full length article
Magnetic interactions and dielectric behaviour of cobalt ferrite and barium titanate multiferroics nanocomposites ⁎
T
⁎
S. Mahalakshmia, , R. Jayasria, S. Nithiyanathamb, , S. Swethaa, K. Santhic a
Department of Physics, Ethiraj college for Women(Autonomous), Chennai 600008, India PG and Research Department of physics, Thiru Vi Ka Government Arts and Science College, Thiruvarur 610003, India c Department of Physics and Nanotechnology, SRM University, Kattankulathur, Chennai 603 609, India b
A R T I C LE I N FO
A B S T R A C T
Keywords: Dielectrics Magnetic Titanate Ferrite Nanophase
Multiferroics materials have been used widely in various fields such as ceramic supercapacitors, active and multifunctional devices due to their high relative permittivity with magnetic and ferroelectric behavior even at room temperature. The composites of cobalt ferrite, barium titanate have been synthesized through co precipitation technique and sintered at very high temperature1273K. The existence of titanate single phase and cobalt ferrite structural analysis carried out through ‘X’ Ray diffraction analysis. From the AC analysis the role of phase, dielectric constant, loss tangent and conductivity was also studied. AC conductivity variation was very low at lower frequencies and increases with frequency. Magnetization measurements were carried out at room temperature shows soft ferromagnetic property is 2.8089 emu/g.
1. Introduction
2. Materials and methods
Cobalt ferrite is a class of ferrite possesses the properties such as magnetostrictive, stable, anisotropic and etc. The material with high permittivity with low power loses are suitable for ferroelectric material of Barium titinate [1,2]. The necessary and the required magnetic and electric coupling behavior can be adjusted with proper tuning of volume ratio by changing the phases between the cobalt ferrite and barium titanate [3–6]. The individual component not exhibiting active properties for the lack of phases while the suitable combination of constituents gives rise to magnetoelectric behavior by suitable phases [7,8]. The composites which are separated in physical sense such as magnetic and electric properties [9]. Magnetoelectric materials which exhibit larger phase coupling among the constituents at room temperature [9]. The physical properties varied by strain through compression, charge carrier by exchanging of ions and exchange of spin are improved in magnetoelective effect and inducing the magnetization by polarization [10]. The multiferroic composites are essential for the fabrication of active devices with more range of frequencies region [11]. Moreover, the single phase multiferroic systems are rare in nature which leads to the preparation of ferromagnetic-ferroelectric composite materials [12,13].
Cobalt ferrite powder was prepared by co-precipitation method. The starting materials are Fe(NO3)3∙9H2O and CO(NO3)3∙6H2O. The metal nitrates were taken in stiochiometric ratio of 1:2 and then dissolved in double distilled water and added with aqueous citric acid solution. The metal nitrates and citric acid were taken in the ratio of 1:1. Then the solution was kept in the magnetic stirrer for 4 h. The NH4OH was added drop by drop to maintainpH7 and constant temperature 353 K throughout the stirring process. After 4 h brown coloured precipitate were obtained. The obtained precipitates were kept in the oven for 20 mins. After self-ignition takes places and the fine powder were obtained. Then the colour of the precipitate turned to black. The particles were sintered at 1273 K for an hour. The obtained powder samples were mixed by using Pestle and Mortar then the nano sized Cobalt ferrite was obtained. BaTiO3 nanoparticles were prepared by the following procedure. The precursors used in this reaction were bariumnitrate and titaniumtetra isoperoxide and ethyleneglycol were taken in the ratio 1:1:2. The mixture was dissolved in minimum amount of deionized water followed by nitric acid in order to have a complete reaction of the powder precursors. The obtained solution was stirred in a magnetic stirrer for 4 h with a constant temperature of 353 K. To maintain the pH 7 ammonium hydroxide was then added drop wise. The solution later turned into a pale whitish precipitate. The precipitate was
⁎
Corresponding authors. E-mail addresses: [email protected] (S. Mahalakshmi), s_nithu59@rediffmail.com (S. Nithiyanatham).
https://doi.org/10.1016/j.apsusc.2019.07.096 Received 20 March 2019; Received in revised form 10 June 2019; Accepted 13 July 2019 Available online 17 July 2019 0169-4332/ © 2019 Published by Elsevier B.V.
Applied Surface Science 494 (2019) 51–56
S. Mahalakshmi, et al.
Fig. 1. IR spectra of cobalt ferrite.
Fig. 2. IR spectra of cobalt ferrite, Barium titanate.
grinded using a mortar and pestle to obtain the uniform distribution of the particles. The obtained powder were sintered 1273 K for 3 h, after sintering the powder it was slowly cooled to room temperature.
Table 1 Characteristic FTIR absorption bands. Functional groups
Vibration mode
Fe-OH/Co-OH OH, C-O C-H MO
Valence vibration Stretching modes stretching stretching Intrinsic valance vibration
Wave number (cm−1) 3433 3402 1080 1643 597
3. Result and discussion 3.1. Spectroscopic analysis Fig. 1 shows the FTIR spectra of cobalt ferrite and it observed that the intense absorption band at 3433 cm−1is corresponds to the valence vibrations of metal hydroxyl (FeeOH and CoeOH) [13]. The presence of the peaks in the range 2000–3000 cm−1 is confirming that the presence of OeH, CeO and CeH stretching modes of vibrations [14]. The broad metal‑oxygen bands are known to be observed in
collected and kept in a heating mantle for an hour to obtain dry powder. The dried particles were sintered at 1000Kfor an hour to obtain perovskite BaTiO3 structure. CoFe2O4 and BaTiO3 were taken in equal ratio were manually 52
Applied Surface Science 494 (2019) 51–56
S. Mahalakshmi, et al.
Cobalt ferrite, Barium titanate
0.8 0.6
cobalt ferrite
M o m e n t (e m u )
0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -15000
-10000
-5000
0
5000
10000
15000
Field (G) Fig. 3. Magnetization curve of cobalt ferrite and cobalt ferrite - Barium titanate.
cubic symmetry of TieO stretching vibration is depicted from the absorption of 596 cm−1. In addition to TieO bonding vibration and TiO6 octahedral bonding [16].
Table 2 Magnetic properties of CoFe2O4 and CoFe2O4-BaTiO3.
CoFe2O4-BaTiO3 CoFe2O4
MS (emu/g)
HC (G)
Mr(emu/g)
44 85
191.55 40.27
7.35 3.81
3.2. Magnetic measurements The magnetisation of sample is measured using LAKESHORE 7410 at room temperature 301 K. The measurement carried out at ordinary envrionment of ranges from −15 to +15 Koe− are magnetically ordered are shown in Fig. 3. The antiparallel spins among the Fe3+ ions in tetrahedral sites, Co2+ ions at octaheral sites of CoFe2O4 are reflected from the loop. The Ms was 85 emu/g for CoFe2O4. The magnetization of CoFe2O4 and BaTiO3 decreases due to the introduction of non-magnetic phase which may reduce the magnetic moment and magnetization [17]. The coercivity HC(Oe) increased with the addition
frequencyυ1observed at 597 cm−1 is corresponding to the intrinsic valence vibrations in tetrahedral positions of Mtetra-O in CoFe2O4 [15]. The FTIR spectra of copper ferrite and barium titanate powders are shown in Fig. 2, the peak observed at 596 cm−1 is indicating the stretching vibrations of M-O band. There is no absorption around 1000 cm−1 is confirming that the non-existence of nitrate ions in the prepared samples (Table 1). It is well known that the barium nitrate has
311
700
Cobalt ferrite
600
400
611 222
200
220
300
111
Intensity
500
511
Sample
100
0 0
20
40
60
2theta(degree) Fig. 4. XRD of cobalt ferrite. 53
80
100
Applied Surface Science 494 (2019) 51–56
S. Mahalakshmi, et al.
3.4. Dielectric studies The dielectric studies of cobalt ferrite nanoparticle are measured using the 50LCRHightester (model no: H10KI3532). The plot of relative permittivity vs frequency of pure composite ofCoFe2O4, BaTiO3, CoFe2O4 - BaTiO3 is shown in Fig. 5. From these Figs, it can be observed that the dielectric constant and loss tangent values decreases largely at lower frequency and gradually maintain the constant values are higher frequencies. The charge transport phenomenon is fully depends on the relaxation time, dielectric constant depends on the frequency. The dielectric dissipation occurring at lower frequency ranges indicating the interfacial polarization otherwise Maxwell Wagren type [18,19] for all prepared samples based on Koop's phenomenological theory [20]. The dissipation of energy at lower frequencies is due to all types of polarization mechanism taking place. At high frequencies the occurrence of space charge polarization exhibiting due to inhomogeneous dielectric structure of grain size, impurities and etc. are confirmed through higher dielectric constant [21]. The larger dielectric constant in ferroelectric due to the surface area is covered by ferrite ions [22]. In addition the interface between ferrite and ferroelectric phases possess different concavity and permittivity values are depicted in Fig. 6. The accumulation of charges on the nonconducting interface gives rise to the interfacial polarization in the composites under influence of electric field. At high frequency range the dielectric constant not coherent and this type of works are reported by many researchers [23–25]. The dissipation of energy by means of heat is called dielectric loss. This may reduce the polarization because of grain size, impurities and compactness due to imperfection. Fig. 7 shows the plot of dielectric loss vs frequency and it can be observed that the losses decreased with increasing frequencies and this may be due to the conduction increases is not favor to lagging polarization through mobile ions, electrons and etc. The accumulation of more charges on the interface were improved with conductivity are observed in Fig. 8. The more accumulation due to polarization at the interface is large with electrical conductivity [26].
Fig. 5. XRD of Barium titanate.
of barium titanate in obtained multiferroic material. The same trend is observed in Mr values also (Table 2).
3.3. Structural studies The XRD of cobalt ferrite nanoparticles and barium titanate were measured using X pert pro diffractometer at room temperature. X-ray diffraction patterns of prepared CoFe2O4 and BaTiO3 as shown in Figs. 4 & 5. The XRD patterns confirm the formation of ferrite structure. X-ray diffraction shows the nature of the material with perfect orientation along the (1 1 1), (2 0 2), (2 2 2), (4 0 0), (3 0 2), (3 2 2), (3 1 1) and (3 3 3) planes (JCPDS File no. 96-591-0064 and ferroelectric phase has perovskite tetragonal structure by JCPDS files No. 05-0626). Using the Scherer equation, the particles size of the crystals in the form of powder is determined of about 25 nm. And these XRD patterns reveals that the cobalt ferrite and barium titanate are shown the predominant phases. From this is it confirmed that the first one is cubic spinel structure and later one is perovskite structure.
4. Conclusions Multifferoiccomposites of CoFe2O4 and BaTiO3were synthesized by co-precipitation method. The FTIR spectra of synthesized powders the Fig. 6. Dielectric constant of cobalt ferrite (■), barium titanate ( ) and cobalt ferrite + barium titanate ( ).
2.0
Cobalt ferrite Barium Titanate Cobalt Ferrite, Barium Titanate
1.8 1.6
Dielectric constant
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 1
2
3
4
5
6
7
LogF (Hz) 54
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S. Mahalakshmi, et al.
Fig. 7. Dielectric loss of cobalt ferrite (■), barium titanate ( ) and cobalt ferrite + barium titanate ( ).
3.0
Cobalt ferrite Barium titanate cobalt ferrite, Barium Titanate
2.5
Dielectric loss
2.0
1.5
1.0
0.5
0.0
1
2
3
4
5
6
7
LogF(Hz)
Fig. 8. Conductivity of cobalt ferrite (■), barium titanate ( ) and cobalt ferrite + barium titanate ( ).
Conductance (Siemens)
0.00020
CoFe2O4 BaTiO3 CoFe2O4- BaTiO3
0.00015
0.00010
0.00005
0.00000
1
2
3
4
5
6
7
LogF (Hz)
peak observed at 596 cm−1, confirmed the stretching vibrations in (TieO) band. Magnetization is less in cobalt ferrite composite rather than pure one. The coercivity increases with the addition of non-magnetic phase barium titanate may reduce the magnetic moment. Dielectric loss develops a lagging behaviour of polarization due to the grain boundaries, imperfection in the crystal lattice and etc., Dielectric loss shown reverse trend with frequency is good for storage and active purpose.
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