F
❖Green synthesize method was successful: The purity and crystalline nature of the synthesized NPs were confirmed with the powder x-ray diffraction studies.
❖From the powder XRD, the size of the NPs were calculated for Fe3O4(22 nm) and Fe2+(Fe0.95Cr0.05)2O4(17 nm) by the Scherrer’s equation.
❖The size of the Fe3O4and Fe2+(Fe0.95Cr0.05)2O4NPs were calculated from the TEM micrograph and the particle sizes is found to be 53 ± 2 nm and 16 ± 2 nm, respectively.
❖Temperature and applied field dependent magnetization measurements confirm the retention of ferrimagnetic behavior up to 300 K.
S. Nagaraj, P. Mohanty, C.J. Sheppard and A.R.E. Prinsloo*
Cr Research Group, Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park, Johannesburg 2006, South Africa
Green Synthesis of Fe 3 O 4 Nanoparticles: Structure and Magnetic Properties
*
Corresponding author email: [email protected]
Introduction
❖Magnetite (Fe3O4) nanoparticles (NPs) is one of the naturally occurring minerals that has importance in paleomagnetic measurements used to study continental drift and it is also found in the mantle wedge of subduction zones [1].
❖Magnetically, Fe3O4orders ferrimagnetically with a Curie temperature of 850 K having an inverse spinel structure,AB2O4, with theAsite occupied by Fe3+and the Bsites populated equally by Fe3+and Fe2+at room temperature [2].
❖Interestingly, Fe3O4demonstrates a metal-insulator transition, popularly known as the Verwey transition, at a temperatureTv= 120 K and below which it shows a two-fold increase in the resistivity [2].
❖As a consequence, theBsites are randomly occupied by Fe2+and Fe3+even at high pressure. Charge ordering can explain the Verwey transition [3].
❖Fe3O4plays an important role as a catalyst in inorganic processes, such as in the synthesis of ammonia and the dehydrogenation of ethyl benzene to styrene [4].
❖Fe3O4is a potential candidate for use in various fields – also in the field of magnetic recording media coupled with the imaging of atomic structure and the electronic properties of the surface where there are high demand at present [4].
❖With the various importance of Fe3O4, the present work aimed to synthesis of Fe3O4NPs using a novel green synthesis approach withAloe arborescensplant extract by the co-precipitation method.
❖The effect doping and synthesis methods on Cr3+at Fe3+site is discussed based on the structure, magnetic properties, particle size and morphology in this work.
Methodology Plant Extract Preparation
Results and Discussion
Conclusion Synthesis of NPs by Co-precipitation Method
X-Ray Diffraction (XRD) pattern
Transmission Electron Microscope (TEM) Micrograph and Size Histogram
Magnetic Properties of NPs: VSM studies
Acknowledgements
References
3. Klotz, S.et al. (2008).Phys. Rev. B,77, 012411.
4. Mariotto, G.et al. (2002).Phys. Rev. B,66, 245426.
❖XRD analyses confirm purity and crystalline nature of the NPs.
❖Average particle size of the crystallites obtained from (311) peak at 35.6°by using Scherrer’s equation:D= 0.89λ/βcosθ. For Fe3O4and Fe2+(Fe0.95Cr0.05)2O4,DXRDwas found as 22 nm and 17 nm, respectively.
❖TEM give shape and size of the NPs, with lattice spacing 0.546 nm from HRTEM.
❖ Magnetic properties of the NPs were studied in a temperature range of 2 <T< 300 K.
❖ Hysteresis loops indicate that the synthesized NPs have ferrimagnetic behaviour.
❖ From hysteresis loops the following parameters are obtained: saturation magnetization (Ms), remanent magnetization (Mr) and coercive field (Hc).
❖Fig. 4 (a) and (b) shows magnetization as a function of temperature, under zero field cooling (ZFC) and field-cooling (FC) modes. Bifurcation to 300 K suggestTc> 300 K.
-4 -2 0 2 4
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
Magnetic moment(emu/g)
Applied field (H) 150K ZFCW
290K ZFCW
-0.01 0.00 0.01 -0.5 0.0 0.5
Magnetic moment(emu/g)
moH(T) 150K ZFCW 290K ZFCW
-4 -2 0 2 4
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3
Magnetic moment(emu/g)
Applied Field(H) 5k ZFCW
150K ZFCW 290K ZFCW
-0.2 0.0
0.0 0.1
Magnetic moment(emu/g)
moH (T) 5k ZFCW 150K ZFCW 290K ZFCW
0 50 100 150 200 250 300
0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30
Magnetic moment(emu/g)
Temperature(K) ZFC
FC moH = 0.005T
0 50 100 150 200 250 300
0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016
Magnetic moment(emu/g)
Temperature(K) ZFC FC
moH = 0.005T
10 15 20 25
0 1 2 3 4 5
Count
Particle size(nm)
35 40 45 50 55 60 65 70
0 1 2 3 4 5
Counts
Particle size(nm)
Fe2+(Fe0.95Cr0.05)2O4
Fe3O4
M(H)
Fe3O4 Fe2+(Fe0.95Cr0.05)2O4
Fe2+(Fe0.95Cr0.05)2O4 Fe3O4
M(T)
Fig. 1 XRD pattern of the NPs indicated in the legend.
10 20 30 40 50 60 70 80
3000 4000 5000 6000 7000 8000 9000 10000
Intensity(a.u)
2q degree Fe3O4 Fe2+(Fe3+0.95Cr3+.05)2 O4 (220)
(311)
(400) (422)
(511) (440)
Fig. 3(a) and (b) M-Hloops for the nanoparticle samples indicated in each panel.
Fig 2 (a), (c) TEM images and (b), (d ) particle size distribution of NPs. Inset in (c) shows HRTEM.
Fig. 4 (a) and (b) Temperature dependent magnetization curves of NPs indicated in each panel.
Plant extract heated for an hour
Dried powder dissolved with ethanol
Filtered Aloe arborescens Plant extract
Financial aid from the SANRF (Grant no. 120856), as well as the University of Johannesburg (UJ) URC and FRC is acknowledged. The use of the NEP Cryogenic Physical Properties Measurement System at UJ, obtained with the financial support from the SANRF (Grant no. 88080) and UJ, RSA, is acknowledged.
The use of the Spectrum facility in the FoS at UJ is acknowledged.
(a) (b)
(c) (d)
(a) (b)
(a) (b)
1. Bengtson, A.et al. (2013).Phys. Rev. B,87,155141.
2. Duffy, J. A.et al. (2010).Phys. Rev. B,81,134.
DTEM=53 ±2 nm
DTEM=16 ±2 nm
