Effect of Cr substitution on CoFe2O4 nanoparticles
M. Vadivel, R. Ramesh Babu*
Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli
620 024, Tamil Nadu, India
* Corresponding Author’s Email: rampap2k@yahoo.co.in Tel: + 91-431-2407057 Fax: + 91-431-2407045
Abstract
TEM analysis
Formation of single phase cubic spinel structure was
confirmed by XRD. TEM observations revealed that the
CoFe2O4 and CoFe2-xCrxO4 nanoparticles are uniformly
distributed and not highly agglomerated. Magnetic properties
revealed that the saturation magnetization of the samples
decreases with increasing Cr concentration and lie in the range
of 69.67- 42.71 emu/g for the prepared samples.
TEM analysis reveals that the prepared nanoparticles
shows regular in shape. Also the average particle size
increases with increasing the Cr concentration up to x =
0.2 concentration, thereafter decreases when compared
with pure CoFe2O4 nanoparticles.
Keywords: Nanoparticle; Chemical synthesis;
diffraction; Dielectric Property; Magnetic Property
Dielectric study reveals that the dielectric constant and
dielectric loss of the prepared nanoparticles increases
with increase in temperature whereas both are decreases
with increasing frequency.
Cobalt ferrite is one of the fascinating magnetic
materials since it possesses strong magnetic anisotropy,
high coercivity at room temperature (5400 Oe),
moderate saturation magnetization (80 emu/g) and good
mechanical and chemical stabilities [1]. In spinel
ferrites, addition of metal cations of different valance
states leads to variety of tetrahedral (A) and octahedral
(B) sites distribution [2].
In the present investigation, pure and Cr substituted
CoFe2O4 magnetic nanoparticles were prepared by coprecipitation method for various concentration of Cr and
the effect of Cr concentration on the structural, spectral,
dielectric, magnetic and optical properties is reported in
the present work.
Synthesis
Cr substituted CoFe2O4 nanoparticles, CoFe2-xCrxO4 (x =
0.0, 0.1, 0.2 and 0.3), were prepared by co-precipitation
method using high purity iron (III) chloride
hexahydrate, cobalt (II) chloride hexahydrate and
chromium (III) chloride hexahydrate.
Magnetic properties
Magnetic measurements show that the saturation
magnetization, retentivity and magneton number
decreases with increasing Cr concentration which may
be due to the weakening of superexchange interaction
between the tetrahedral A site and octahedral B site in
the ferrites.
80
60
40
CoFe2O4
CoFe1.9Cr0.1O4
CoFe1.8Cr0.2O4
CoFe1.7Cr0.3O4
20
0
Ms
70
-20
Saturation Magnetization (emu/g)
Introduction
Dielectric properties
Magnetization (emu/g)
X-ray
-40
-60
60
55
50
45
40
-80
-20000
65
0.00
-15000
-10000
-5000
0
5000
0.05
0.10
0.15
0.20
Cr concentration
10000
0.25
15000
0.30
20000
Magnetic Field (Oe)
Results and discussion
X-ray diffraction analysis
XRD peaks reveal that the prepared samples belong to a
single phase cubic spinel structure. The crystallite size
varies from 15 to 23 nm. Lattice constant slightly
increases for x = 0.1 and thereafter it decreases
gradually from the value of CoFe2O4. The variation in
lattice constant may be attributed to the replacement of
Fe3+ ions (ionic radius 0.64 Å) by relatively smaller
ionic radius (0.63 Å) Cr3+ ions. The porosity of the
synthesized samples decreases with increasing Cr
concentration.
Fig.1 Magnetic hysteresis loops of CoFe2-xCrxO4
nanoparticles at room temperature (inset) The variation
in saturation magnetization (Ms) with different Cr
concentrations
Acknowledgement
One of the authors MV is thankful to UGC-BSR, Govt.
of India for the award of ‘Research Fellowship in
Science for Meritorious Students-2013’. The authors are
thankful to Dr. M. Arivanandhan for TEM analysis.
References
FTIR spectral analysis
The symmetric stretching vibration of Fe-O (metaloxygen) band at the tetrahedral site is observed at
587 cm-1.
[1] Y. Qu, H. Yang, N. Yang, Y. Fan, H. Zhu, G. Zou,
Mater. Lett. 60 (2006) 3548.
[2] S. Singhal, S. Jauhar, J. Singh, K. Chandra, S.
Bansal, J. Mol. Struct. 1012 (2012) 182.