Magnetic, dielectric and impedance spectroscopy
study of BiFeO3 multiferroic nanoceramics
K. P. Bera, P. R. Mandal, T.K. Nath*
Department of physics, Indian Institute of Technology Kharagpur, 721302, West Bengal, India
*Corresponding author’s e-mail: tnath@phy.iitkgp.ernet.in
Abstract
We report structural, magnetic, dielectric
properties of BiFeO3nanoceramicssynthesized by sol-gel
technique. DTA-TGA analysis indicates the signature of
ferroelectric and magnetic phase transitions. The room
temperature dielectric constant and tanδare found to be
615and 0.087, respectively. P-E loops exhibits ferroelectric
nature. The magnetic measurements shows strong
ferromagnetism.
Keywords: Ferromagnetism, relaxation, dielectric behavior,
ferroelectricity, impedance spectroscopy.
space group R3c. The Rietveldrefinement confirms that
the sample is well crystallized without having any
impurity phases. The DTA curve (shown in Fig. 1)
shows an exothermic peak at 325 OC and an
endothermic peak at 805 OC corresponding to Neel and
Cure temperature respectively. TG curve shows small
weight lossof 0.26 % with increasing temperature from
270 to 540OC. The coexistence of Fe2+ and
Fe3+(observed from XPS spectra as shown in the inset of
Fig. 1) may be the plausible reason of enhance
ferromagnetism. 1.2
10
O
30 C
O
100 C
O
200 C
8
0
14.1
13.8
-10
2.7
Fe 2p3/2
-20
3+
Fe
2.4
DTA
14.4
Intensity x 103(a.u)
TG (%)
14.7
2+
Fe
-30
-40
2.1
714
0
711
708
B.E.(eV)
300 600
T (oC)
-50
900 1200
Fig.1: DTA-TG curve
Novel chemical sol-gel route has been used to
synthesizethe nanometric BFO powder using Bi(NO3)3,
5H2O and Fe(NO3)3,9H2O. The final powders
arecalcined at 500 OC for 3 hours. The particle size are
observed to be 50-70 nm obtaining from FESEM
micrograph analysis.
ExperimentalResults
The Rietveld refinement of the XRD data has
been performed using rhombohedral structure with
3
1.0
4
'x10
2
0.8
0
1
2
10
10
3
10
0.6
30
5
10
6
10
7
10
O
C
O
100 C
200
10
2.4
2
0.2
P (C/cm2)
1.8
4
10
f (Hz)
0.4
Z"X106(ohm)
Multiferroic materials exhibit simultaneously the
coexistence of ferroelectricity and ferromagnetism in
same crystallographic phase. Due to the magnetoelectric
coupling they have potential application in data storage
device, spintronics, microelectronics etc. Among all
perovskites (ABO3type) BiFeO3 (BFO) exhibits room
temperature multiferroicity. Synthesis of pure BFO in
bulk phases as well as in nanometric phase is
challenging due to the unwanted appearance of Fe-rich
impurity phases during synthesis.Careful synthesis,
doping, and epitaxial thin film growth etc. help to
overcome the high leakage current, suppressionof the
superior FE polarization and superimpose of spiral spin
modulation on G-type AFM ordering [1].
6
tan 
Introduction
(a)
0.1
10
O
C
3
5.0 kV/cm
10.0 kV/cm
12.5 kV/cm
15.0 kV/cm
4
10
10
f (Hz)
5
10
6
250
275
2.5 Hz
-0.1
7
300 K
0.0
300
-0.2
1.2
10
325
-15 -10 -5 0 5
E (kV/cm)
10 15
350
O
O
O
O
O
C
C
C
C
C
0.6
(b)
0.0
0.0
0.5
1.0
1.5
Z'X106(ohm)
2.0
2.5
Fig.2: (a) Frequency dependent ε' at different
temperatures (Inset shows tanδ versus frequency at
different T). (b) Nyquist plots at different T. (Inset
shows room temperature P-E loops at 2.5 Hz)
The high value (700 at 100 Hz) of low
frequency ε' at room temperature is attributed to the
Maxwell-Wagner
type
polarization.
Impedance
spectroscopy shows non Debye type relaxation
behavior. The decrease of Z' with increase in
temperature indicate the semiconductor like behavior of
nanometric BFO. The activation energy (1.31 eV) has
been calculated from the frequency corresponding to Z"
maxima versus 1/T plot (not shown here) using
Arrhenius law. The P-E loops (room temperature)
indicate the ferroelectric behavior of the sample. The
magnetic measurement reveals strong ferromagnetic
nature of nanometric BFO.
Reference
[1]. V. Goianet. al.J. Appl. Phys. C 110, 074112
(2011).