Field-Temperature History Dependence of Resistivity
and Enhanced Magnetoresistance in
(Nd0.7-xGdx)Sr0.3MnO3 (x = 0-0.3)
Nanoparticles
S. Kundu1*, T. K. Nath2
Department of Physics, Rajiv Gandhi University of Knowledge Technologies,
Nuzvid 521202, Andhra Pradesh, India
2
Department of Physics and Meteorology, Indian Institute of Technology,
Kharagpur 721302, India
*
Corresponding author’s e-mail:souravphy@gmail.com
Abstract
The measured resistivity of (Nd0.7-xGdx)Sr0.3MnO3 (x =
0, 0.1, 0.2, 0.3) in magnetic field or without magnetic field
is found to strongly depend on the cooling history (in or
absence of field) of the samples. The observed effects are
attributed to phase separation and arrest of phase in the
samples.
Keywords: Magnetoresistance, Manganite, Nanoparticles,
Phase separation, Phase arrest.
Introduction
In a manganite like RMnO3, (R = Rare earth
elements) appropriate substitution of the trivalent
elements (R) with divalent materials (like Sr2+ and Ca2+
etc.) introduces ferromagnetism and metallicity
accompanied with a colossal magnetoresistance effect
governed mainly by the so called double exchange
mechanism. However, it has also been found that
substitution of the trivalent ion with a different trivalent
ion (like the rare earth elements), in a double exchange
ferromagnetic manganite introduces many other
fascinating effects including change in bandwidth and
phase separation [1]. Further, the reduction grain size
down to the nanometric regime introduces additional
effects in the system [2]. Our investigations deal with
the field temperature history effect in Gd-doped
Nd0.7Sr0.3MnO3 bulk and nanometric samples.
Results and discussion
Our samples of bulk and nanometric (with
average grain size 50-60 nm) polycrystalline (Nd0.7xGdx)Sr0.3MnO3 (x = 0, 0.1, 0.2, 0.3) have been
synthesized through chemical route and are found to be
of single phase.
Temperature (3-300 K) and field (0-8 T)
dependence of resistivity of all the samples has been
measured. A history dependence of resistivity is found
in the samples. Precisely, the measured resistivity
during warming of the samples as a function of
temperature (in the absence of field or with field) has
been found to strongly depend on the field at which the
sample was cooled (Fig. 1). This history effect is also
enhanced on size reduction as well as on increment of
the Gd concentration. Further we have investigated any
possible dependence of magnetoresistance (MR) on Gd
doping and reduction of grain size. It has been found
that the MR at low temperature is enhanced due to the
reduction of grain size and increase in the Gd
concentration in the system. The observed effects are
best explained through modification of the phase
separation on size reduction and Gd substitution. It also
appears that the electronic phase of the systems is
arrested after field cooling.
ZFC_W_0T
FC_W_1T
FC_W_5T
FC_W_8T
7
10
 (ohm-cm)
1
6
10
5
10
Nd0.4Gd0.3Sr0.3MnO3
4
10
3
10
0
20
40
60
80
100
120
140
160
T (K)
Fig.1: Measured resistivity of x = 0.3 nanometric
sample during warming at zero field with different
cooling history. FC_W: field-cooled-warming.
Conclusions
In summary, we can say that the low
temperature field-cooled phase of the samples does not
come back to its original high temperature phase during
warming. The phase remains arrested.
References
[1] K. F. Wang et al., “Cluster-glass state in manganites
induced by A-site cation-size disorder”, Phys. Rev. B
73, (2006)134411.
[2] P. Dey and T. K. Nath, , Phys. Rev. B 73, (2006)
214425.