Evolution of Ferrimagnetism in Co(Cr1xAlx)2O4
(x = 0.0  1.0)
Rajender Padam, Seenipandian Ravi and Dilip Pal *
Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781039, India
Corresponding author’s e-mail: [email protected], Tel.: +91-361-258 2720; Fax: +91-361-258 2749
*
Abstract
We present the evolution of detailed magnetic
properties in Co(Cr1xAlx)2O4 samples for x = 0.01.0.
With increasing the Al concentration ‘x’ the magnetization
enhances and ferrimagnetic nature observed in CoCr2O4,
become ferromagnetic-like upto x = 0.5, thereafter it
becomes antiferromagnetic. With ‘x’ the magnetic
ordering temperature decreases continuously and the
magneo-structural transition around 26 K get weakened
and vanishes at higher Al concentration.
ferromagnetic for x=1.0. Ferrimagnetic ordering
temperature TC decreases gradually with ‘Al’
concentration and the sharpness of transition can be
seen to decrease upto x = 0.5 and start showing glassy
type antiferromagnetic behavior for the samples above x
 0.6. The magneo-structural transition around 26 K in
parent CoCr2O4 also get weakened and vanishes at
higher Al concentration. Detailed analysis will be
presented.
Keywords: Magnetic oxides, spinel, ferrimagnet,
magnetization curves, CoCr2O4.
FC
x = 0.5
Co(Cr1xAlx)2O4
Introduction
H = 1 kOe
1
TS ~ 26 K
x = 0.0
FC
TC ~ 50 K

Multiferroics is the active area of current research
because of their promising multifunctional capabilities
and the fundamental interest [1]. In the recent years
CoCr2O4 has conceived lot of attention as it is among
very few multiferroic materials in which the electric
polarization is completely originates from the
microscopic magnetic ordering [2,3]. Local magnetic
ordering lonely dictates the coupling between the
electric and magnetic properties in this compound.
Hence the study of magnetic properties is the essential
part of multiferroics. Substitution of different elements
into its different sites give the comprehensive
understanding of the underlying magnetic properties
[4,5].
M ( B/f.u )
ZFC
ZFC
FC
x = 0.8
ZFC TN
0.1
TC ~ 96 K
(~12 K)
x=1
TN (~9 K)
0
20
40
60
80
100
120
140
T(K)
In this report we try to comprehend the influence of
‘Al’ substitution for ‘Cr-site’ on the structural and
magnetic properties of CoCr2O4.
Fig. 1: The temperature dependent variation of the
magnetization of the Co(Cr1-xAlx)2O4 samples for the
applied field of 1 kOe.
Results and Discussions
Acknowledgment
The polycrystalline samples of Co(Cr1-xAlx)2O4 for
x=0.01.0 are prepared by sol-get method. Fig.1 depicts
the temperature dependent magnetization (M) of Co(Cr1sample measured in the zero field cooled
xAlx)2O4
(ZFC) field cooled (FC) modes for the applied field (H)
of 1 kOe. With increase in the ‘Al’ concentration ‘x’ M
enhances enormously and show almost one order
change for x=0.5 with ferromagnetic behavior. Above
x=0.5, M decreases and the ordering become anti-
Authors are grateful to Prof. S. Ramakrishnan and Prof.
A. K. Grover of TIFR for availing the experimental
facilities.
References
[1]
[2]
[3]
[4]
[5]
James F Scott, Nature materials 5, 22 (2013)
Y. Yamasaki et al., PRL 96, 207204 (2006).
Y. J. Choi et al., PRL 102, 067601 (2009).
I. Kim et al., APL 94, 042505R (2009).
R. Padam et al., APL 102, 112412 (2013).