- Email: [email protected]
Tailoring the Structural and Magnetic Properties and of Nickel Ferrite by Auto Combustion Method
Available online at www.sciencedirect.com
ScienceDirect Procedia Materials Science 6 (2014) 1725 – 1730
3rd International Conference on Materials Processing and Characterisation (ICMPC 2014)
Tailoring the structural and magnetic properties and of nickel ferrite by auto combustion method T. Shanmugavel1, S. Gokul Raj2,*, G. Rajarajan3, G. Ramesh Kumar4 1
Department of Physics, Paavai Engineering College, Pachal – 637 018, India Department of Physics, Vel Tech University, Avadi, Chennai – 600 062, India 3 Department of Physics, Selvam College of Technology, Namakkal – 637 003, India Department of Physics, University College of Engineering Arni, Anna University Chennai, Arni – 632 317, India *Email: [email protected] 2
4
Abstract Nickel ferrite (NiFe2O4) is synthesized by using auto combustion method with citric acid as a chelating agent. The formation of single phase nickel ferrite was confirmed through powder X-ray diffraction. The vibrational analysis was confirmed through fourier transform infrared spectroscopic (FTIR) analysis. The compositional analysis was confirmed through energy dispersive X-ray analysis (EDS). Surface morphology, crystalline form of NiFe2O4 was also investigated through transmission electron microscopic (TEM) analysis. Magnetic measurements showed the ferromagnetic behaviour with curie temperature at 500 °C which is in agreement with that of the reported values. The results were discussed in detail. © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
© 2014 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Gokaraju Rangaraju Institute of Engineering and Technology (GRIET). Selection and peer review under responsibility of the Gokaraju Rangaraju Institute of Engineering and Technology (GRIET)
Keywords: Magnetic; Spinel Ferrites; Autocombustion method; Surface Morphology; Grain size.
1. Introduction The aim of this study is to develop and suitable process to produce nanoferrites using auto combustion technique. Ferromagnetic properties of the material depend very much on the particle or grain size. When the particle size is large, compare to the single domain size then the material act as a hard magnet. If the particle size smaller than the single domain size the material act as a soft magnet. ________________ * Corresponding author.
E-mail address: [email protected]
2211-8128 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer review under responsibility of the Gokaraju Rangaraju Institute of Engineering and Technology (GRIET) doi:10.1016/j.mspro.2014.07.158
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T. Shanmugavel et al. / Procedia Materials Science 6 (2014) 1725 – 1730
However, ferromagnetic materials only have ferromagnetic properties over a certain critical size. The ferromagnetic materials become super magnetic, due to the disordering of magnetic moments below its critical size, which is caused by thermal disturbance. Nanosized spinel ferrite particles, a kind of soft magnetic materials with structural formula of MFe2O4 (M = divalent metal ion, e.g. Mn, Mg, Zn, Ni, Co, Cu, etc.), are one of the most attracting class of materials due to their interesting and important properties such as low melting point, high specific heat capacity, large expansion coefficient, low saturation magnetic moment and low magnetic transition temperature, etc (Tian.MB. 2001, Xu. Q. et al. 2009). Nickel ferrite is one of the versatile and technologically important soft ferrite materials because of its typical ferromagnetic properties, low conductivity and thus lower eddy current losses, high electrochemical stability, catalytic behavior, abundance in nature, etc (Gunjakar et al. 2008). This ferrite is an inverse spinel in which eight units of NiFe2O4 go into a unit cell of the spinel structure. Half of the ferric ions preferentially fill the tetrahedral sites (A-sites) and the others occupy the octahedral sites (B-sites) (Goldman. 1993). The synthesis of spinel ferrite nanoparticles has been intensively studied in the recent years and the principle role of the preparation conditions on the morphological and structural features of the ferrites is discussed (De guire. 1989, li. 2000, ferreira et al. 2003, manova et al. 2004). Large-scale applications of ferrites with small particles and tailoring of specific properties have prompted the development of widely used chemical methods, including hydrothermal , sonochemical reactions (shafi et al. 1998), microwave plasma (hochepied et al. 2000), co-precipitation (kim et al. 2003), micro emulsion methods (Feltin and Pileni 1997), citrate precursor techniques(Prasad et al. 1998) and mechanical alloying (shi et al. 1999) for the fabrication of stoichiometry and chemically pure spinel ferrite nanoparticles. The sol-gel route is one of the most commonly used techniques due to its economics and high degree of compositional control. Nanocrystalline nickel ferrite, NiFe 2O4, was successfully prepared via reaction between metal nitrates solution with surfactant assisted processes. Investigations on the particle size, morphology and magnetic properties of inverse spinel nickel ferrite in at different conditions are carried out by the XRD, TEM, and VSM techniques. 2. Experimental Techniques 2.1 Materials and methods All the chemicals used in this experiment Ni (NO3)2·6H2O, Fe (NO3)3·9H2O and citric acid were of analytical grade and also used without further purification. Chemicals are weighed carefully in electronic balance using spatula nickel nitrate and iron nitrate were diluted in the distilled water in the proposed manner. They are mixed together the solution is continuously stirred using a magnetic stirrer and constantly maintained the temperature at 80 °C. Citric acid acts as a chelating agent mixed with the solution with the ratio of 1:1. Condensation reaction occurs between the adjoining metal nitrates and the molecules of citrates yielding a polymer network in colloidal dimensions known as sol. Continuous heating of xero gel leads to the formation of nano powder of NiFe2O4 through a auto combustion process until all the gel was burnt out completely to form loose powder. The powder was then calcined at a temperature of 700 °C. 2.2 Characterization analyses The structure was studied using X-ray diffraction spectrometer using Philips PW 1820 diffractometer with Cu Kα radiation. FTIR spectrum for the powder sample was recorded in the range from 400 to 4000 cm −1 at room temperature using Bruker IFS 66V FTIR spectrometer. The particle size and surface morphology were examined through transmission electron microscope (TEM) JEOL JEM 2100 using high resolution transmission electron microscope (HRTEM) 200 Kv Japan. Magnetic measurements were carried out using a superconducting vibration sample magnetometer (Oxford Instruments) with a maximum field of 80 kOe in the temperature range from 5K to room temperature. Temperature dependent magnetization was measured using the same instrument fitted with high temperature (HT) set-up for the samples calcinated at 700 °C for the maximum applied field of 10 kOe.
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3. Results and discussion 3.1. X-ray diffraction
@ 700° C
(620)
(440)
(511)
(422)
(400)
(222)
(311)
(220)
(111)
Relative Intensity (a.u)
XRD data was used to determine the structural parameters of all the samples. All the XRD peaks can be indexed to the cubic spinel structure with no extra lines corresponding to any other planes, which show that the prepared ferrites are single phase. The broadened nature of these diffraction peaks indicates that the grain sizes of the sample is on nano meter scale. The mean crystallite size was calculated from the XRD line width of (311) peak using
JCPDS 74-2081
10
20
30
40
50
60
70
80
2T (deg) Fig. 1. Powder X–ray diffraction patterns of (a) JCPDS 74-2081; (b) NiFe2O4 at 700 °C.
Debye-Scherrer equation: ܦൌ ͲǤͻߣȀߚߠ݊݅ݏ
(1)
D stands for crystalline size, λ is the wavelength of the radiation, β is the full width at half maximum (FWHM in radians) centered at 2θ of the most intense peak at (311) (Konig and Chol 1968, Chae et al. 2004, Gupta et al. 2007). The miller indices help us to identify the planes of the crystal. The hkl indices of the sample are (111), (220), (311), (222), (400), (422), (511), (440) and (620) as plotted in fig. 1 All the peaks of the XRD pattern were indexed and D-spacing values are plotted in the tabulation below (Tab.1). Table 1. D spacing values for each plane. 2θ (°)
hkl Planes
D – spacing (nm)
16.415
111
3.533
30.294
220
1.448
35.685
311
2.514
37.329
222
2.407
43.373
400
2.085
53.819
422
1.702
57.376
511
1.604
63.013
440
1.474
71.504
620
1.318
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T. Shanmugavel et al. / Procedia Materials Science 6 (2014) 1725 – 1730
3.2. EDS analysis The energy dispersive spectroscopy's X-ray detector measures the number of emitted X-rays compared to their energy. The energy of the X-ray is characteristic of the element from which the x-ray was emitted. A spectrum of the energy versus relative counts of the detected X-rays is obtained and evaluated to determine quality and quantity of elements present in the sample. EDS measurement results comply with what is expected from the synthesis. In other words, mass ratios of chemical compositions are in agreement with the outcomes of the EDS (Fig.2). The experimental mass percentage and atom percentage for the sample are given in the Table-2.
Fig. 2. EDS for NiFe2O4 at 700 °C. Table 2. Experimental mass percentage and atom percentage of Ni Fe2O4. Element
Mass %
Atom %
OK Fe K Ni K
42.59 44.34 13.07
72.36 21.58 06.05
3.2. Magnetic measurement analysis Fig.3 shows the hysteresis loop of nickel ferrite calcinated at 700 °C. The magnetisation curves displays higher Ms value of 31 emu/g, this value somewhat lower than bulk values. The hysteresis loop show essentially small coercivity, improved crystallites and higher magnetisation. Coercive field value is decrease it can be attributed to larger magneto crystalline anisotropy characteristic nickel ferrite. At room temperature the coercivity is large due to the scattering in direction of anisotropy field due to inhomogeneous broadening. At high temperature, it has the tendency to make magnetic moment isotropic causes the coercivity to decrease. 40
Ni700 30
10 0 0.6
-10
Moment
0.5
Moment (emu/g)
Moment (emu/gm)
20
-20
NiFe2o4
0.4
0.3
0.2
0.1
-30
0.0 0
100
200
300
400
500
600
o
Temperature C
-40 -10000
-5000
0
5000
10000
Field (Oe)
Fig. 3. Hysteresis loop for NiFe2O4 at 700 °C.
T. Shanmugavel et al. / Procedia Materials Science 6 (2014) 1725 – 1730
Fig. 4. FE-SEM for NiFe2O4 at 700 °C.
Fig. 5. TEM for NiFe2O4 at 700 °C.
3.2 SEM and TEM analysis Fig.4 shows the field emission scanning electron micrographs (FE-SEM) of nickel ferrite. Scanning electron micrographs (SEM) images indicate that the samples consist of cubic shaped with the existence of soft agglomeration and also it shows that clear boundary between neighbouring crystallites can be observed. In order to investigate the morphology and particle size, the TEM images of samples were obtained and it is shown in Fig. 5. The particles are roughly spherical and have a crystalline size in the range of 45-55 nm. The particles are more or less spherical and are more agglomerated for due to magnetic property of ferrite nanocrystals and their distribution is quite complicated. Average grain-size obtained from TEM image of sample is approximately 60 nm, which is in good agreement with the size determined by XRD patterns. 4. Conclusion Nanocrystalline nickel ferrite powder has been successfully synthesized by auto combustion method. The Structural, morphology and magnetic properties of the obtained materials have been studied. The formation of single phase is confirmed by the XRD technique. SEM and EDS measurement showed the chemical composition, element distribution and homogeneity of the nanocrystalline powder. The crystalline size is increased when compared with asprepared sample it shows that increase in temperature increase its crystallite size. The magnetic properties of low coercivity and saturation magnetisation, it is used in preparation magnetic storage devices. The prepared nanocrystalline combustion method at low temperature pure and uniform in nature, there is no agglomeration formed. Further investigations on preparation of the other magnetic ferrites at various temperatures are in progress. Acknowledgements One of the authors T. Shanmugavel wishes to thank to all the Management members and Department of Physics, and various department staff members of Paavai Engineering College, Namakkal – 637 018, for providing a platform to perform the research.
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References Chae. K.P., Lee. J.G., Kweon. H.S., Lee. Y.B., 2004, The crystallographic,Magnetic properties of Al,Ti doped CoFe2O4 powders grown by solgel method, J.Magn.Magn.Mater, 283, 103-108. De Guire. M., 1989, The cooling rate dependence of cation distributions in CoFe2O4. J Appl Phys. 65(8), 3167–3172. Feltin. N., Pileni. MP., 1997, New Technique for Synthesizing Iron Ferrite Magnetic Nanosized Particles.Langmuir. 13,3927–3933. Ferreira. TAS., Waerenborgh. JC., Mendonsa. MHRM., Nunes. MR., Costa. FM., 2003, Structural and morphological characterization of FeCo2O4 and CoFe2O4 spinels prepared by a coprecipitation method. Solid State Sci. 5(2), 383–392. Goldman. A., 1993, Modern Ferrite Technology, New York: Marcel Dekker. Gunjakar. JL., More. AM., Gurav. KV., Lokhande. CD., 2008, Chemical synthesis of spinel nickel ferrite (NiFe2O4) nano-sheets. Appl Surf Sci. 254(18), 5844–5848. Gupta. N., Verma. A., Kashyap. S.C., Dube. D.C., 2007, Microstructural, dielectric and magnetic behavior of spin-deposited nanocrystalline nickel-zinc ferrite thin film for microwave applications, J.Magn.Magn.Mater. 308, 137-142. Hochepied. JF., Bonville. P., Pileni. MP., 2000, Nonstoichiometric Zinc Ferrite Nanocrystals: Syntheses and Unusual Magnetic Properties. J Phys Chem. 104(5), 905–912. Kim. YI., Kim. D., Lee. CS., 2003, Synthesis and characterization of CoFe2O4 magnetic nanoparticles prepared by temperature-controlled coprecipitation method. Phys B(Amestherdam, Neth) 337,42–51. Konig. U., Chol. G., 1968, X-ray and neutron diffraction in ferrites of MnxZn1-xfe2O4 type,J.Appl. Crystallogr.1, 124-126. Li. S., 2000, Cobalt-ferrite nanoparticles: Structure, cation distributions, and magnetic properties. J Appl Phys. 87(9),6223–6225. Manova. E., Tsoncheva. T., Paneva. D., Mitov. I., Tenchev. K., Petrov. L., 2004, Mechanochemically synthesized nano-dimensional iron-cobalt spinel oxides as catalysts for methanol decomposition. Appl Catal A. 277(1-2), 119–127. Prasad. S., Gajbhiye. NS., 1998, Magnetic studies of nanosized nickel ferrite particles synthesized by the citrate precursor technique. J Alloys Compd. 265, 87–92. Shafi. KVPM., Gedanken. A., Prozorov. R., Balogh. J., 1998, Sonochemical Preparation and Size-Dependent Properties of Nanostructured CoFe2O4 Particles. Chem Mater.10 (11), 3445–3450. Shi. Y., Ding. J., Liu. X., Wang. J., 1999, NiFe2O4 ultrafine particles prepared by co-precipitation/mechanical alloying. J Magn Magn Mater. 205, 249–254. Tian. MB. 2001, Magnetic Material. Beijing , Tsinghua University Press. Xu. Q., Wei. Y., Liu. Y., Ji. X., Yang. L., Gu. M., 2009, Preparation of Mg/Fe spinel ferrite nanoparticles from Mg/Fe-LDH microcrystallites under mild conditions. Solid State Sci. 11(2), 472–478.
ScienceDirect Procedia Materials Science 6 (2014) 1725 – 1730
3rd International Conference on Materials Processing and Characterisation (ICMPC 2014)
Tailoring the structural and magnetic properties and of nickel ferrite by auto combustion method T. Shanmugavel1, S. Gokul Raj2,*, G. Rajarajan3, G. Ramesh Kumar4 1
Department of Physics, Paavai Engineering College, Pachal – 637 018, India Department of Physics, Vel Tech University, Avadi, Chennai – 600 062, India 3 Department of Physics, Selvam College of Technology, Namakkal – 637 003, India Department of Physics, University College of Engineering Arni, Anna University Chennai, Arni – 632 317, India *Email: [email protected] 2
4
Abstract Nickel ferrite (NiFe2O4) is synthesized by using auto combustion method with citric acid as a chelating agent. The formation of single phase nickel ferrite was confirmed through powder X-ray diffraction. The vibrational analysis was confirmed through fourier transform infrared spectroscopic (FTIR) analysis. The compositional analysis was confirmed through energy dispersive X-ray analysis (EDS). Surface morphology, crystalline form of NiFe2O4 was also investigated through transmission electron microscopic (TEM) analysis. Magnetic measurements showed the ferromagnetic behaviour with curie temperature at 500 °C which is in agreement with that of the reported values. The results were discussed in detail. © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
© 2014 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Gokaraju Rangaraju Institute of Engineering and Technology (GRIET). Selection and peer review under responsibility of the Gokaraju Rangaraju Institute of Engineering and Technology (GRIET)
Keywords: Magnetic; Spinel Ferrites; Autocombustion method; Surface Morphology; Grain size.
1. Introduction The aim of this study is to develop and suitable process to produce nanoferrites using auto combustion technique. Ferromagnetic properties of the material depend very much on the particle or grain size. When the particle size is large, compare to the single domain size then the material act as a hard magnet. If the particle size smaller than the single domain size the material act as a soft magnet. ________________ * Corresponding author.
E-mail address: [email protected]
2211-8128 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer review under responsibility of the Gokaraju Rangaraju Institute of Engineering and Technology (GRIET) doi:10.1016/j.mspro.2014.07.158
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T. Shanmugavel et al. / Procedia Materials Science 6 (2014) 1725 – 1730
However, ferromagnetic materials only have ferromagnetic properties over a certain critical size. The ferromagnetic materials become super magnetic, due to the disordering of magnetic moments below its critical size, which is caused by thermal disturbance. Nanosized spinel ferrite particles, a kind of soft magnetic materials with structural formula of MFe2O4 (M = divalent metal ion, e.g. Mn, Mg, Zn, Ni, Co, Cu, etc.), are one of the most attracting class of materials due to their interesting and important properties such as low melting point, high specific heat capacity, large expansion coefficient, low saturation magnetic moment and low magnetic transition temperature, etc (Tian.MB. 2001, Xu. Q. et al. 2009). Nickel ferrite is one of the versatile and technologically important soft ferrite materials because of its typical ferromagnetic properties, low conductivity and thus lower eddy current losses, high electrochemical stability, catalytic behavior, abundance in nature, etc (Gunjakar et al. 2008). This ferrite is an inverse spinel in which eight units of NiFe2O4 go into a unit cell of the spinel structure. Half of the ferric ions preferentially fill the tetrahedral sites (A-sites) and the others occupy the octahedral sites (B-sites) (Goldman. 1993). The synthesis of spinel ferrite nanoparticles has been intensively studied in the recent years and the principle role of the preparation conditions on the morphological and structural features of the ferrites is discussed (De guire. 1989, li. 2000, ferreira et al. 2003, manova et al. 2004). Large-scale applications of ferrites with small particles and tailoring of specific properties have prompted the development of widely used chemical methods, including hydrothermal , sonochemical reactions (shafi et al. 1998), microwave plasma (hochepied et al. 2000), co-precipitation (kim et al. 2003), micro emulsion methods (Feltin and Pileni 1997), citrate precursor techniques(Prasad et al. 1998) and mechanical alloying (shi et al. 1999) for the fabrication of stoichiometry and chemically pure spinel ferrite nanoparticles. The sol-gel route is one of the most commonly used techniques due to its economics and high degree of compositional control. Nanocrystalline nickel ferrite, NiFe 2O4, was successfully prepared via reaction between metal nitrates solution with surfactant assisted processes. Investigations on the particle size, morphology and magnetic properties of inverse spinel nickel ferrite in at different conditions are carried out by the XRD, TEM, and VSM techniques. 2. Experimental Techniques 2.1 Materials and methods All the chemicals used in this experiment Ni (NO3)2·6H2O, Fe (NO3)3·9H2O and citric acid were of analytical grade and also used without further purification. Chemicals are weighed carefully in electronic balance using spatula nickel nitrate and iron nitrate were diluted in the distilled water in the proposed manner. They are mixed together the solution is continuously stirred using a magnetic stirrer and constantly maintained the temperature at 80 °C. Citric acid acts as a chelating agent mixed with the solution with the ratio of 1:1. Condensation reaction occurs between the adjoining metal nitrates and the molecules of citrates yielding a polymer network in colloidal dimensions known as sol. Continuous heating of xero gel leads to the formation of nano powder of NiFe2O4 through a auto combustion process until all the gel was burnt out completely to form loose powder. The powder was then calcined at a temperature of 700 °C. 2.2 Characterization analyses The structure was studied using X-ray diffraction spectrometer using Philips PW 1820 diffractometer with Cu Kα radiation. FTIR spectrum for the powder sample was recorded in the range from 400 to 4000 cm −1 at room temperature using Bruker IFS 66V FTIR spectrometer. The particle size and surface morphology were examined through transmission electron microscope (TEM) JEOL JEM 2100 using high resolution transmission electron microscope (HRTEM) 200 Kv Japan. Magnetic measurements were carried out using a superconducting vibration sample magnetometer (Oxford Instruments) with a maximum field of 80 kOe in the temperature range from 5K to room temperature. Temperature dependent magnetization was measured using the same instrument fitted with high temperature (HT) set-up for the samples calcinated at 700 °C for the maximum applied field of 10 kOe.
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3. Results and discussion 3.1. X-ray diffraction
@ 700° C
(620)
(440)
(511)
(422)
(400)
(222)
(311)
(220)
(111)
Relative Intensity (a.u)
XRD data was used to determine the structural parameters of all the samples. All the XRD peaks can be indexed to the cubic spinel structure with no extra lines corresponding to any other planes, which show that the prepared ferrites are single phase. The broadened nature of these diffraction peaks indicates that the grain sizes of the sample is on nano meter scale. The mean crystallite size was calculated from the XRD line width of (311) peak using
JCPDS 74-2081
10
20
30
40
50
60
70
80
2T (deg) Fig. 1. Powder X–ray diffraction patterns of (a) JCPDS 74-2081; (b) NiFe2O4 at 700 °C.
Debye-Scherrer equation: ܦൌ ͲǤͻߣȀߚߠ݊݅ݏ
(1)
D stands for crystalline size, λ is the wavelength of the radiation, β is the full width at half maximum (FWHM in radians) centered at 2θ of the most intense peak at (311) (Konig and Chol 1968, Chae et al. 2004, Gupta et al. 2007). The miller indices help us to identify the planes of the crystal. The hkl indices of the sample are (111), (220), (311), (222), (400), (422), (511), (440) and (620) as plotted in fig. 1 All the peaks of the XRD pattern were indexed and D-spacing values are plotted in the tabulation below (Tab.1). Table 1. D spacing values for each plane. 2θ (°)
hkl Planes
D – spacing (nm)
16.415
111
3.533
30.294
220
1.448
35.685
311
2.514
37.329
222
2.407
43.373
400
2.085
53.819
422
1.702
57.376
511
1.604
63.013
440
1.474
71.504
620
1.318
1728
T. Shanmugavel et al. / Procedia Materials Science 6 (2014) 1725 – 1730
3.2. EDS analysis The energy dispersive spectroscopy's X-ray detector measures the number of emitted X-rays compared to their energy. The energy of the X-ray is characteristic of the element from which the x-ray was emitted. A spectrum of the energy versus relative counts of the detected X-rays is obtained and evaluated to determine quality and quantity of elements present in the sample. EDS measurement results comply with what is expected from the synthesis. In other words, mass ratios of chemical compositions are in agreement with the outcomes of the EDS (Fig.2). The experimental mass percentage and atom percentage for the sample are given in the Table-2.
Fig. 2. EDS for NiFe2O4 at 700 °C. Table 2. Experimental mass percentage and atom percentage of Ni Fe2O4. Element
Mass %
Atom %
OK Fe K Ni K
42.59 44.34 13.07
72.36 21.58 06.05
3.2. Magnetic measurement analysis Fig.3 shows the hysteresis loop of nickel ferrite calcinated at 700 °C. The magnetisation curves displays higher Ms value of 31 emu/g, this value somewhat lower than bulk values. The hysteresis loop show essentially small coercivity, improved crystallites and higher magnetisation. Coercive field value is decrease it can be attributed to larger magneto crystalline anisotropy characteristic nickel ferrite. At room temperature the coercivity is large due to the scattering in direction of anisotropy field due to inhomogeneous broadening. At high temperature, it has the tendency to make magnetic moment isotropic causes the coercivity to decrease. 40
Ni700 30
10 0 0.6
-10
Moment
0.5
Moment (emu/g)
Moment (emu/gm)
20
-20
NiFe2o4
0.4
0.3
0.2
0.1
-30
0.0 0
100
200
300
400
500
600
o
Temperature C
-40 -10000
-5000
0
5000
10000
Field (Oe)
Fig. 3. Hysteresis loop for NiFe2O4 at 700 °C.
T. Shanmugavel et al. / Procedia Materials Science 6 (2014) 1725 – 1730
Fig. 4. FE-SEM for NiFe2O4 at 700 °C.
Fig. 5. TEM for NiFe2O4 at 700 °C.
3.2 SEM and TEM analysis Fig.4 shows the field emission scanning electron micrographs (FE-SEM) of nickel ferrite. Scanning electron micrographs (SEM) images indicate that the samples consist of cubic shaped with the existence of soft agglomeration and also it shows that clear boundary between neighbouring crystallites can be observed. In order to investigate the morphology and particle size, the TEM images of samples were obtained and it is shown in Fig. 5. The particles are roughly spherical and have a crystalline size in the range of 45-55 nm. The particles are more or less spherical and are more agglomerated for due to magnetic property of ferrite nanocrystals and their distribution is quite complicated. Average grain-size obtained from TEM image of sample is approximately 60 nm, which is in good agreement with the size determined by XRD patterns. 4. Conclusion Nanocrystalline nickel ferrite powder has been successfully synthesized by auto combustion method. The Structural, morphology and magnetic properties of the obtained materials have been studied. The formation of single phase is confirmed by the XRD technique. SEM and EDS measurement showed the chemical composition, element distribution and homogeneity of the nanocrystalline powder. The crystalline size is increased when compared with asprepared sample it shows that increase in temperature increase its crystallite size. The magnetic properties of low coercivity and saturation magnetisation, it is used in preparation magnetic storage devices. The prepared nanocrystalline combustion method at low temperature pure and uniform in nature, there is no agglomeration formed. Further investigations on preparation of the other magnetic ferrites at various temperatures are in progress. Acknowledgements One of the authors T. Shanmugavel wishes to thank to all the Management members and Department of Physics, and various department staff members of Paavai Engineering College, Namakkal – 637 018, for providing a platform to perform the research.
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