Magneto-dielectric behavior of Sm2CoMnO6
P.R.Mandal, R. Sahoo, and T.K.Nath*
Department of Physics, Indian Institute of Technology Kharagpur, 721302, West Bengal, India
*
E-mail: tnath@phy.iitkgp.ernet.in, Tel.: +91-9932952097
Single phase double perovskite Sm2CoMnO6 is
prepared by chemical sol-gel route. The magnetic study
reveals multiple magnetic transitions at 137 and 105 K. A
positive magnetodielectric (MD) effect follows the
dielectric relaxation. The activation energy predicts the
thermally activated dielectric relaxation.
Keywords: Magneto-dielectric, spin-orbit coupling.
Introduction
4
-6
Tc
-4
-2
0
2
4
6
2
Tc
1
100 Oe
0
50
-14
-16
4
0.005
4
3
0.006 0.007
1/T (K -1)
0.008
1 kHz
100 kHz
2
2
H(T)
0
a
1
0
-1
-2
FC
2
E =0.19 eV
-12
5
0
-20
ZFC
6
MD%
M(emu/gm)
6
M(emu/gm)
5K
20
12 K
-10
 ' x10
40
8
-8
8
3
Double perovskite with the general formula of
A2B'B"O6 (A-rare earth; B', B"-transition metals) have
gained much scientific interest for having variety of
interesting physics and technological applications.
Double perovskite La2CoMnO6 gains considerable
attention due to its ferromagnetic nature and good
magneto-dielectric behavior near room temperature.
The substitution of La3+ by the rare earth ions with
smaller ionic radius changes the physical properties by
changing the B'-O-B" bond angles and exchange
interactions.
downturn in the magnetization at the lowest temperature
(12 K) is attributed to the effect of the spin-orbit
coupling of Co-Mn network on the magnetic ordering of
rare earth Sm3+. The paramagnetic to ferromagnetic
phase transition is observed to be T C1 ~ 137 K and it is
followed by a second transition at T C2 ~ 105 K. Due to
small ionic radius of Sm3+ the Co-O-Mn bond angel will
be decreased by decreasing the superexchange
interaction which will decrease the Curie temperature as
compare to the Curie temperature of La2CoMnO6 [1].
TC1 is attributed to Co2+/Mn4+ FM superexchange
interaction. TC2 ̴is assigned to the FM vibronic
superexchange interaction of intermediate spin Co3+ and
high spin Mn3+ [1]. The incomplete saturation (30.2
emu/gm) in M-H curve (shown in the inset of Fig. 1) at
5 K may be attributed to the existence of antisite
disorder.
ln 
Abstract
100 150 200 250 300
T(K)
of Sm2CoMnO6 under
Fig. 1: M-T curves
FC-ZFC
conditions at 100 Oe. Inset shows the M-H plot at 5 K.
Results and discussions
Sm2CoMnO6 sample has been synthesized by
conventional chemical sol-gel route and sintered at
1150°C for 5 hours. Sm2CoMnO6 crystallizes in a
perovskite structure with monoclinic P21/n space
groups. Figure 1 shows temperature dependent
magnetization of Sm2CoMnO6 at the applied magnetic
field of 100 Oe under zero field cooled and field cooled
condition in the temperature range of 5 K to 300 K. The
fitting line fitted by Curie-Weiss law in the inverse
susceptibility vs. temperature plots (not shown here) cut
the positive axis in the temperature axis which confirms
the ferromagnetic behavior of Sm2CoMnO6. The
0
0
-50
0
100
200
T (K)
50
300
100 150
T (K)
1 MHz
200
250
300
Fig. 2: Dielectric constant vs. temperature plots of
Sm2CoMnO6 at 0 T at the frequency range of 1 kHz to 1
MHz. Upper inset shows the Arrhenius plot obtained
from dielectric loss peak. Lower inset shows the MD
behavior at 100 kHz frequency.
Figure 2 shows the temperature dependent real
part of dielectric permittivity. With increasing
temperature the dielectric permittivity increases with
two steps like features. The temperature dependent
magneto-dielectric effect (MD) at 5 T field measured at
100 kHz is shown in the lower inset of Fig. 2. The MD
value reaches the maximum at around ~ 210 K which
corresponds to the first dielectric peak. The relaxation
mechanism is analyzed by the thermally activated
Arrhenius behavior (as shown in the upper inset of Fig.
2) and the activation energy is observed to be 0.19 eV.
References
[1] K. D. Truong, J. Laverdie`re, M. P. Singh, S. Jandl,
and P. Fournier, Phys. Rev. B 76, 132413 (2007).