Accepted Manuscript Synthesis of Superparamagnetic Particles of Mn1-xMgxFe2O4 Ferrites for Hyperthermia Applications Aisha Iftikhar, M.U. Islam, M.S. Awan, Mukhtar Ahmad, Shahzad Naseem, M. Asif Iqbal PII: DOI: Reference:
S0925-8388(14)00508-8 http://dx.doi.org/10.1016/j.jallcom.2014.02.138 JALCOM 30723
To appear in: Received Date: Revised Date: Accepted Date:
20 June 2013 27 December 2013 22 February 2014
Please cite this article as: A. Iftikhar, M.U. Islam, M.S. Awan, M. Ahmad, S. Naseem, M. Asif Iqbal, Synthesis of Superparamagnetic Particles of Mn1-xMgxFe2O4 Ferrites for Hyperthermia Applications, (2014), doi: http:// dx.doi.org/10.1016/j.jallcom.2014.02.138
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Synthesis of Superparamagnetic Particles of Mn1-xMg xFe2O4 Ferrites for Hyperthermia Applications Aisha Iftikhara., M.U. Islama*, M.S. Awanb , Mukhtar Ahmad a, Shahzad Naseemc M. Asif Iqbald, a
Department of Physics, Bahauddin Zakariya University, Multan 60800, Pakistan
b
Center for Micro and Nano Devices, Department of Physics, COMSATS Institute of Information Technology, Islamabad, Pakistan c
d
Centre for Solid State Physics, University of the Punjab, Lahore
College of E &ME, National University of Science and Technology, Islamabad, Pakistan *
Corresponding author +92 61 9210343; Fax +92 61 9210068. Email addresses:
[email protected]
Abstract A series of Mn1-xMgxFe2O4 (x = 0.0-1.0) spinel ferrites were synthesised by chemical coprecipitation. The materials were investigated by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometry. Xray diffraction patterns for all the samples revealed single phase formation with particle size below 100nm. The lattice constant was observed to decrease as the Mg-substitution increases thus altering the unit cell volume. Transmission electron micrographs exhibit that the particles are spherically shaped and agglomerated with particle size ranging 52-100nm quite consistent with particle size obtained from XRD data. The M-H loops for all the samples are narrow with low values of coercivity and retentivity, indicate the super-paramagnetic nature of these samples. Based on these characterizations of the samples it is suggested that the Mn1xMgxFe2O4
ferrites may be potential candidates for hyperthermia applications.
Keywords: Spinel ferrites; Nano-particles; Co-precipitation; Hyperthermia.
1
1. Introduction Hyperthermia has attracted a lot of attention in the recent years. The idea that a localized rise in the temperature can be used to destroy malignant tissues selectively is called hyperthermia. The magnetic powder is injected into the body of the patient and heated to produce local temperature of 43oC by the application of ac magnetic field. The mechanism of heating for ferromagnetic material critically depends on hysteresis loss. In the case of super paramagnetic particles, heating can occur by the rotation of particles themselves or by the rotation of atomic magnetic moments [1]. The challenging work is the development of magnetic particles with high specific absorption rate (SAR), which allows reduction of ferrofluid dose in vivo. SAR depends on several parameters such that particle magnetization, size and distribution, ac magnetic field and frequency [2]. By controlling the particle size of magnetic particles, one can adjust the heat generation under an oscillating magnetic field [3]. Mn–Zn ferrites are potential magnetic materials high initial permeability, low losses, high saturation magnetization and relatively high Curie temperature having wide applications like soft magnetic powders, hyperthermia, magnetic fluids, heat transfer systems [4,5], transformer core, high velocity magnetic record, resonance magnetic imaging [6] and as magnetoelectric composites [7,8]. For the applications of MFe2O4 (where M2+ = Mn2+, Zn2+, Fe2+, Co 2+, Ni2+, etc.) for future magnetic micro devices to integrate drug delivery systems, a compromise between magnetic moment and absence of magnetic remanent memory is desired, like in super paramagnetic particles [9]. Also the use of magnetostrictive ferrite phase is important and promising to trigger on magnetic-mechanically stimulated drug delivery systems [10]. The possibility of preparing ferrites in the form of nano particles has open a new and exciting research field with revolutionary applications not only in the electronic technology but also in the field of biotechnology. A remarkable characteristic of spinel structure is that the composition of a given ferrites can be strongly modified while the basic crystalline structure remain the same. Synthesis parameters, composition and microstructure have strong influence on the properties of ferrites. Mix ferrites are very important from technological point of view and substitution of metal cations in ferrites is optimized for having a specific property in the final substituted ferrite for particular application. The crystallographic, electrical and magnetic properties of these ferrites significantly depend on their method of synthesis, chemical composition, sintering or annealing temperature, substitution of cations and grain size etc. [11–13]. These parameters control the
2
microstructure forming of the high resistive boundaries between the constituent grains. Properties of ferrites have also been strongly exaggerated when the particle size approaches a critical diameter, below which each particle is considered to be a single domain [14]. Recently, several methods have been used for the synthesis of highly crystalline and uniformly sized magnetic particles of ferrites [15–17]. For the preparation of ferrofluid and magnetic particles with excellent chemical homogeneity, the chemical co-precipitation technique is widely used. This method has gained scientific and technological importance during the last decades. This process offers many advantages as compared to the conventional ceramic method, such as low temperature processing and/or better homogeneity for the synthesis of multi-component materials and thus formation of the homogenized particles of ferrites. The objective of this study is to synthesize and investigate the structural and magnetic properties of Mn-Mg ferrites particles suitable for hyperthermia applications.
2. Experimental 2.1 Synthesis The Mg-substituted Mn1-xMgxFe2O4 ferrites were prepared by co-precipitation. Analytical grade manganese chloride (MnCl2.4H2O), magnesium oxide (MgO) and iron chloride (FeCl3) were used as starting materials to obtain Fe3+, Mn2+, Mg2+ ions in aqueous solutions. After stoichiometric calculations the required amount of parent materials was dissolved in deionized water. The solutions containing these ions were mixed in an appropriate molar proportion in 1000ml beaker. The solution was heated to 60 oC with continuous stirring and the solution of NaOH and Na2CO3 (with ratio1:4) was used in order to maintain the pH(1112) value of the solution. The solution of NaOH and Na2CO3 was added slowly drop-wise into reactant solution with constant stirring until precipitation is completed. The precipitates were washed off by deionized water for many times. Samples were dried in an oven for 24 hr at 100oC. The dried powder was sintered at 1000oC for 6 hr followed by the furnace cooling. 2.2 Characterization The crystal structure of the prepared ferrite powders was identified by Schimadzu X-ray diffractometer (XD5A) using CuKα (λ = 1.5406Å) radiations at room temperature. The surface morphology and microstructure of the samples were studied using a transmission electron microscope TEM (JEOL model JEM1010). The elemental composition was determined by energy dispersive X-ray spectroscopy (EDXS) using JED-2300 instrument: 6490(LA). M-H loops were measured at room temperature using a vibrating sample magnetometer (VSM) Model Lake Shore, new 7400 series, USA. 3
3. Results and discussion 3.1 X-ray diffraction analysis X-ray diffraction patterns for all Mg-substituted Mn ferrites have been shown in Fig. 1. Several reflections corresponding to characteristic interplanar spacing were observed. All the indexed peaks belong to the spinel cubic structure which confirms the formation of single phase cubic spinel structure with no traces of impurity phase. Furthermore, lattice constant a and volume of unit cell V for each concentration were calculated by the following relations respectively [18],
Sin 2θ =
λ2 2a 2
(h 2 + k 2 + l 2 )
V= a3
(1) (2)
Here λ is the wavelength, a, the lattice constant and hkl are the corresponding Miller indices. The calculated values of lattice constants and unit cell volume for all the samples are given in Table 1. It can be observed that the values are in good agreement with earlier reported values for this structure [19]. The results also show that value of lattice constant ‘a’ of un-substituted sample is greater than those of substituted ones. The reduction in the lattice constant with increasing Mg-concentration could be explained on the basis of the fact that ionic radius of Mg2+ (0.66Å) is less than that of Mn2+ (0.91Å) [11, 19]. The particles size D was calculated by using the Scherrer formula [18], D = kλ/βcosθB
(3)
where β is the full width half maxima, k is a shape factor = 0.9, λ is the wavelength of incident X-ray. The average particle size fall in the range of 50-100 nm listed in the Table 1 that indicates the nano-size of the particles.
3.2 The EDX Analysis The EDX spectra as shown in Fig. 2 for the samples exhibit the presence of only dissolved reactants of Mn, Mg, Fe, O and C contents. The traces of Al and C are due to the sample stub. Table 2 shows the observed EDX quantitative data (Molecular wt %) of the dissolved reactants for the representative samples.
4
3.3 Transmission Electron Microscopy The samples were examined with transmission electron microscope in order to determine the size and study the morphology of the nano-particles.TEM micrographs of Mg substituted Mn ferrites are shown in Fig 3 for the representative samples x = 0.0,0.3,0.5. The particles are nearly spherical in shape and agglomerated to some extent. Because of smaller size (single domain) particles experience permanent magnetic moment hence each particle is permanently magnetized and get agglomeration.TEM micrographs show fine particles size of ferrites distributed uniformly. The size of particles is in the range of 50-100nm which is quite consistent with XRD data.
3.4 Magnetic Properties Fig. 4 shows the M-H loops for all of the investigated samples at room temperature. The loops show the low values of remanence and coercivity. The loops for all the samples exhibit the super paramagnetic behaviour except x = 1.0, with very low values of coercivity. It has been reported earlier that such a low value of coercivity may be suitable for hyperthermia applications [20]. The coercivity Hc, saturation magnetization Ms and retentivity Mr decreased with the increase of Mg concentration except x = 1.0 as shown in Fig.5. The changes in magnetic properties such as coercivity Hc , saturation magnetization Ms and retentivity Mr of nano-particles are due to the influence of surface effect, cationic stoichiometry and their occupancy in the specific sites [21-22]. The magnetic order of spinel ferrite is due to the super exchange interaction mechanism of metal ions at A and B sites. The replacement of Mn2+ ions by Mg2+ ions (with zero magnetic moment at B-site) resulted in the reduction of super-exchange interaction between A and B sites. As Mg is non-magnetic and it can occupy both A and B sublattices but preferentially occupy B-sites [13]. The net magnetic moment of whole lattice is the difference between the A- and B-sublattices i.e M = MB-MA where M A and MB are the magnetization of the A and B sites respectively. Therefore a decrease in Ms and Mr can be attributed to weakening of the super-exchange interactions among A-O-B [23]. The squareness ratios (Mr /Ms) ranging (0.07-0.15) is well below the typical value of 1 for a single domain [23]. The calculated values of squareness ratio for Mg-substituted Mn ferrites are listed in Table 1. The values of remanance, coercivity and squareness ratio reveal that these samples are suitable candidates for hyperthermia applications except x=1.
5
Conclusions Single phase Mn1-xMgxFe2O4 ferrite particles were successfully synthesized by chemical coprecipitation. The grain size of particles varie from 50 to 100 nm as measured from TEM and XRD data. The values of Ms and Mr are lower for substituted samples as compared to those for pure one. It is concluded that the samples with x = 0.2, 0.3, 0.5 are super-paramagnetic and may be recommended for the hyperthermia applications.
Acknowledgement The authors are thankful to the Director National Institute for Bio Technology and Genetic Engineering (NIBGE) Faisalabad and his team member Mr. Javed Iqbal for providing facilities for TEM.
References [1]
Pankhurst Q A, Connolly J, Jones SK, Dobson J, J. Phys. D Appl. Phys. (2003), 36: (167-181).
[2]
M. Ma, Y.Wu, J. Zhu,Y .Sun, Y. Zhang, N.Gu, J. Magn. Magn. Mater. 268 (2004) 33.
[3]
Hergt R, Dutz. S, Muller R, Zeisberger M, J. Phys Cond. Matter. 2006:18 (2919-34).
[4]
B. Jeyadevan, C.N. Chinnasamy, K. Shinoda, K. Tohji, J. Appl. Phys. 93 (2003) 8450–8452.
[5]
J. Azadmanjiri, J. Non-Cryst. Sol. 353 (2007) 4170–4173.
[6]
S. Gubbala, H. Nathani, K. Koizol, R.D.K. Misra, Physica B 348 (2004) 317–328.
[7]
N. Cai, J. Zhai, C.W. Nan, Y. Lin, Z. Shi,
[8]
C.F. Zhang, X.C. Zhong, Y.H. Yu, Z.W. Liu, D.C. Zeng, Physica B 404 (2009)
Phys. Rev. B 68 (2003) 224103.
2327–2331. [9]
S. Ya nes-Vilar, M. Sanchez-Andu jar, C. Go ´mes-Aguirre, J. Mira, M.A. Sen arı sRodrı guez, S. Castro-Garcı, J. Solid State Chem. 182 (2009) 2685–2690.
[10]
C.W. Nan, Y. Lin, J.H. Huang, Ferroelectrics 280 (2002) 153–163.
[11]
Alex Goldman,“Modern Ferrite Technology”, Second ed., Springer, New York, 2006.
[12]
Sagar E. Shirsath, R.H. Kadam, Anil S. Gaikwad, Ali Ghasemi, Akimitsu Morisako, J. Magn. Magn Mater 323 (2011) 3104–3108.
[13]
J. Smith, H.P.J. Wijn, “Ferrites”, Wiley, New York, 1959.
6
[14]
C. Kittle, Physical Review 70 (1946) 965–971.
[15]
V. Pillai, D.O. Shah, J. Magn. Magn. Mater 163 (1996) 243–248.
[16]
Y. Ahn, E.J. Choi, S. Kim, H.N. Ok, Materials Letters 50 (1) (2001) 47–52.
[17]
S.T. Alone, Sagar E. Shirsath, R.H. Kadam, K.M. Jadhav, J. Alloys and Compounds 509 (2011) 5055–5060.
[18]
B.D. Cullity, “Elements of X-rays diffraction,” Second Edition. Addison Wesley Publishing Co., Philippines, 1978, Ch 10, P.338.
[19]
L. John Berchmans, R. Kalai Selvan, P.N. Selva Kumar, C.O. Augustin, J. Magn. Magn. Mat. 279 (2004) 103-110.
[20]
Mortaza Mozaffari, Behshid Behdadfar, Jamshid Amighian, J. Pharm. Sci. 4 (2008) 115-118.
[21]
R. Arulmurugan, G. Vaidyanathan, S. Sendhilnathan, B. Jeyadevan, J. Magn. Magn. Mater.298 (2006) 83-94.
[22]
Daiki Shigeoka, Hikaru Katayanagi, Yuki Moro,Shinji Kimura, Toshiyuki Mashino, Yuko Ichiyanagi, J. Phys 200 (2010) 122002.
[23] I. Panneer, Muthuselvam, R.N. Bhowmik, J. Magn.Magn.Mater.322 (2010) 767-776.
List of Tables Table 1 Lattice constant (a), particles size (D), unit cell volume (V), squareness ratio for all Mn1-xMgxFe2O4 ferrites. Table 2 Quantitative data as determined from EDXS analysis for representative ferrite samples Mn1-xMgxFe2O4 (x = 0.0, 0.3, 0.5).
List of Figures Fig. 1 XRD patterns for all Mn1-xMgxFe2O4 ferrites(x = 0.0, 0.1, 0.2, 0.3, 0.5, 1.0). Fig. 2 EDX spectra (a-c) Vs Mg-concentration for representative Mn1-xMgxFe2O4 (x=0.0, 0.3, 0.5) ferrites. Fig. 3 TEM micrographs
a) MnFe2O4 b) Mn0.7Mg0.3Fe2O4 c) Mn0.5Mg0.5Fe2O4
Fig. 4 M-H loops for all Mn1-xMgxFe2O4 ferrites(x = 0.0, 0.1, 0.2, 0.3, 0.5, 1.0). Fig.5 Coercivity (Hc), Saturation Magnetization (Ms), Remanance (Mr), Vs MgConcentration (x) for Mn1-xMgxFe2O4 ferrites(x = 0.0, 0.1, 0.2, 0.3, 0.5, 1.0).
7
440
422
400
311
220
200
x=1.0
Intensity (a.u)
x=0.5
x=0.3 x=0.2 x=0.1 x=0.0 20
30
40
50
60
70
80
2-Theta (degree)
Fig. 1 XRD patterns for Mn1-xMgxFe2O4 ferrites(x=0.0, 0.1, 0.2, 0.3, 0.5, 1.0).
8
(a)
(b)
(c) Fig. 2 EDX spectra (a-c) Vs Mg-concentration for representative Mn1-xMgxFe2O4 (x=0.0, 0.3, 0.5) ferrites.
9
Fig. 3 TEM micrographs
a) MnFe2O4 b) Mn0.7Mg0.3Fe2O4 c) Mn0.5Mg0.5Fe2O4
10
80
Magnetization (emu/g)
60 40 20
x=0.0 x=0.1 x=0.2 x=0.3 x=0.5 x=1.0
0 -20 -40 -60 -80 -10000
-5000
0
5000
10000
Applied field (Oe)
Fig. 4 M-H loops for all Mn1-xMgxFe2O4 ferrites(x=0.0, 0.1, 0.2, 0.3, 0.5, 1.0).
11
Mr(emu/g)
10 8 6
Ms(emu/g)
4
70 68 66 64 62 60 58 56 54 52 50 48
140
Hc(Oe)
120 100 80 60 0.0
0.2
0.4
0.6
0.8
1.0
Mg-Concentration(x)
Fig.5 Hc, Ms, Mr Vs Mg- concentration(x) for Mn1-xMgxFe2O4 ferrites(x=0.0, 0.1, 0.2, 0.3, 0.5, 1.0).
12
Samples
a
Dxrd
V
Mr/Ms
Mn1-xMgxFe2O4
( )
(nm)
( 3)
x=0.0
8.500
72.3
614.13
0.15
x=0.1
8.490
50.2
611.96
0.12
x=0.2
8.485
92.4
610.88
0.07
x=0.3
8.480
79.2
609.80
0.08
x=0.5
8.475
55.4
608.72
0.08
x=1.0
8.470
79.2
607.65
0.12
Table 1 Lattice constant (a), particle size (Dxrd ) unit cell volume (V), squareness ratio( Mr/Ms) for all Mn1-xMgxFe2O4 ferrites(x=0.0, 0.1, 0.2, 0.3, 0.5, 1.0).
Sample
x=0.0
x=0.3
x=0.5
Element Molecular Molecular Molecular Wt%
Wt%
Wt%
Mn
9.70
9.36
8.80
Mg
0.00
0.35
1.42
Fe
79.13
78.11
79.16
O
8.83
8.43
8.73
C
1.94
3.37
1.88
Total
100
100
100
Table 2 Quantitative data as determined from EDXS analysis for representative ferrite samples Mn1-xMgxFe2O4 (x=0.0,x= 0.3, x=0.5).
13
Highlights ¾ Single phase ferrites particles were successfully synthesized by chemical coprecipitation. ¾ With the increase of Mg concentration the lattice constant was decreased. ¾ The grain size of particles was below 100 nm. ¾ The value of Hc for all the samples revealed that the samples are super-paramagnetic. ¾ The samples x= 0.2, 0.3, 0.5 were found to be super-paramagnetic and may be recommended for the hyperthermia applications.
14
80
Magnetization (emu/g)
60 40 20
x=0.0 x=0.1 x=0.2 x=0.3 x=0.5 x=1.0
0 -20 -40 -60 -80 -10000
-5000
0
5000
10000
Applied field (Oe)
M-H loops for all Mn1-xMgxFe2O4 ferrites(x=0.0, 0.1, 0.2, 0.3, 0.5, 1.0).
15
