Structural, Magnetic and Dielectric properties of
La0.4Bi0.6TiO3 Perovskite Oxide
Punith Kumar V.1, R. L. Hadimani2, A. M. Awasthi3, D. C. Jiles2 and Vijaylakshmi Dayal1*,
1
Department of Physics, Maharaja Institute of Technology-Mysore, Karnataka-571438, India
Department of Electrical and Computer Engineering, Iowa State University, Ames IA 50011, USA.
3
Thermodynamics lab, UGC-DAE CSR, University campus, Khandwa Road, Indore-452001, India
*
Corresponding author’s e-mail: drvldayal@gmail.com , Tel.: +91-9620228132; Fax: 08236292601
2
Abstract
We report the structural, magnetic, Raman and dielectric
properties of the polycrystalline La0.4Bi0.6TiO3 perovskite
oxide. The sample has been prepared by conventional solid
state route method. The phase formation and morphology is
characterized using X-Ray diffraction and scanning electron
microscopy respectively. The average grain size of the sample
is found to be ~10.9 nm. To understand the bond stretching
and bending vibrations Raman spectroscopy has been carried
out on the sample. Further the magnetic and dielectric
interactions in the sample are studied using results obtained
from magnetization and dielectric measurements.
Keywords: Perovskite Oxide; Magnetization; Dielectric loss.
Introduction
Bismuth doped lanthanum titanates are interesting for
its unusual magnetic and dielectric properties [1]. The
substitution of trivalent cation such as Bi3+ at La3+ sites
has been extensively studied due to its ferromagnetic
insulating (FMI) behavior [2]. Since Bi3+ lone pair with
6s2 character justifies the strong tendency of the charges
to localize and order. An orientation of the 6s2 lone pair
can produce a local distortion or even hybridization
between Bi-6s-orbits and O-2p-orbits. This behavior
favors dielectric behavior in these types of materials.
without any magnetic saturation upto the measured field
of H=2.5T. But small remnant magnetization (Mr≈
0.00425emu/gm) can be observed which also confirms
that the sample is not purely a PM type but consists of
small FM clusters buried in the host PM matrix. The
dielectric permittivity (ε1) vs. T measured at three
different frequencies (f=1, 10 and 100 kHz) are shown
in Fig.1c. The ε1 curve show characteristic three peaks
at T=150K, T=205K and T=255K which can be
attributed to dielectric relaxation, formation of short
range FM clusters (as observed from CW plot) and
leakage current due to oxygen loss respectively. We
also show dielectric loss vs. T for the sample at
frequencies f=1, 10 and 100 KHz (inset of Fig.1c)
where dielectric loss is maximum at low temperature
but shows crossover behavior above T=205K. This
advert crossover is also reflected as a characteristic
deviation in magnetization CW plot. This suggest the
correlation of both magnetization and dielectric
properties near T=205K.
Experimental
Polycrystalline La 0.4 Bi0.6 TiO3 is been synthesized
using conventional solid state reaction method. The
grown sample is been characterized using XRD, SEM.
The magnetization measurements are carried out using a
MPMS-SQUID. Dielectric measurements are performed
using NOVO-CONTROL-Alpha-A impedence analyzer.
Results and discussions
The sample crystallizes into tetragonal perovskite
structure and can be indexed to I4/mcm space group
with lattice parameters a= 5.578 Ao, b=5.578 Ao and
c=7.612 Ao. The SEM image at 3μm resolution shows
well defined grains and grain boundaries (fig. not
shown). Raman spectrum measured confirms the
perovskite structure of the sample (fig. not shown). The
magnetization (M) vs. Temperature (T) plotting is
shown in Fig.1a. The sample shows paramagnetic (PM)
like behavior with small traces of FM clusters appearing
around T=200K. The Curie-Weiss (CW) plot is shown
in Fig.1b where a characteristic deviation at T d=205 K is
observed. This suggests the existence of short range FM
clusters buried in the host PM matrix. In the inset of
Fig.1a the magnetization (M) vs. field (H) plots at
T=10K and 60K is shown which follows PM behavior
Fig. 1: (a) M vs. T. (b) H/M vs. T with linear fitting is shown.
(c) ε1 vs. T at f=1, 10, 100 kHz is shown in left side and tanδ
vs. T at f=1, 10 kHz is shown in right side. Inset shows tanδ
vs. T at f=100 kHz.
Conclusion
The studied sample exhibit coexistence of PM and
short range FM clusters at T=205K which constitutes
correlation between magnetization and dielectric
properties.
Acknowledgment
This work is supported as YSR Award via project sanction
No: 2011/20/37P/01/BRNS to VD by DAE-BRNS India.
References
[1] Peng Liu, Xiao-Lin Wang, Zhen-Xiang Cheng, Yi Du, and
Hideo Kimura, Phys. Rev. B 83 (2011) 144404.
[2] E.L. Nagaev, Phys. Rep. 346 (2001) 387.