J Supercond Nov Magn (2013) 26:1421–1428
DOI 10.1007/s10948-012-1830-8
ORIGINAL PAPER
Effect of Ni Doping on the Structural, Magnetic and
Magnetocaloric Properties of Pr
0.7
Ca
0.3
Mn
1−y
Ni
y
O
3
Manganites
A. Selmi · W. Cheikhrouhou-Koubaa · M. Koubaa ·
A. Cheikhrouhou
Received: 9 November 2012 / Accepted: 30 November 2012 / Published online: 28 December 2012
© Springer Science+Business Media New York 2012
Abstract In this paper, we report the structural, mag-
netic, and magnetocaloric properties of Ni-doped Pr
0.7
Ca
0.3
Mn
1−y
Ni
y
O
3
(0 ≤ y ≤ 0.1) powder samples. Our com-
pounds were synthesized using the solid state reaction
method at high temperature. X-ray diffraction analysis us-
ing Rietveld refinement show that all our samples are sin-
gle phase and crystallize in the orthorhombic structure with
the Pnma space group. Magnetization measurements ver-
sus temperature in a magnetic applied field of 50 mT reveal
that Ni doping leads to a paramagnetic-ferromagnetic tran-
sition with a Curie temperature increasing from 106 K for
y = 0.02 to 118.5 K for y = 0.1. A large magnetic entropy
change |S
M
| has been observed in our doped samples with
maximum values around their respective Curie temperatures
T
C
. |S
max
M
| is found to be 2 J kg
−1
K
−1
, 2.96 J kg
−1
K
−1
and 2.94 J kg
−1
K
−1
for y = 0.02, 0.05, and 0.1, respec-
tively, in a magnetic field change of 5 T. Large relative
cooling power (RCP) value of 352.24 J kg
−1
is obtained for
Pr
0.7
Ca
0.3
Mn
0.9
Ni
0.05
O
3
sample under 5 T.
Keywords Manganese oxides · X-ray diffraction ·
Isothermal magnetization · Magnetocaloric effect
1 Introduction
In the last few years, a renewed and increasing interest has
been devoted to the study of materials with magnetocaloric
A. Selmi · W. Cheikhrouhou-Koubaa · M. Koubaa ·
A. Cheikhrouhou ()
Laboratoire de Physique des Matériaux, Faculté des Sciences
de Sfax, Sfax University, B.P. 1171, 3000 Sfax, Tunisia
e-mail: abdcheikhrouhou@yahoo.fr
A. Cheikhrouhou
Institut NEEL, B.P. 166, 38042 Grenoble Cedex 9, France
properties for their potential technological applications in
the refrigeration area. This alternative aims to substitute
nongreen chemical gases as CFC and HCFC used for clas-
sical refrigeration at room temperature [1]. Therefore, it is
important to characterize new promising magnetic materi-
als for magnetic refrigeration in a large temperature range.
The MCE is the working principle of the magnetic refrig-
eration technology, which is more energy efficient and en-
vironmental friendly compared to the conventional vapor-
compression-based refrigeration. The MCE is expressed in
terms of either adiabatic temperature change (T
ad
) or
isothermal magnetic entropy change (S
M
) upon a variation
in the external magnetic field [2, 3]. The perovskite man-
ganites with general formula R
1−x
A
x
MnO
3
(R=La
3+
, Pr
3+
etc, and A=Sr
2+
, Ca
2+
, etc.), which became famous due
to their colossal magnetoresistance properties, show much
larger S
M
than other transition metal oxides. They also
exhibit first-order magnetostructural transition for certain
combinations of R and A cations and doping level (x )[4].
In contrast to numerous reports on magnetocaloric ef-
fect in ferromagnetic manganites [5–10], there are only a
handful of reports on the magnetocaloric effect in charge
ordered manganites [11–16]. In fact, we generally need a
magnetic applied field H> 20 T to destroy the charge
ordered (CO) antiferromagnetic state, especially for lower
band width manganites. Hence, the MCE is quite small in
charge ordered manganites for H ≤ 5 T. A detailed study re-
ported by Reis et al. [11] in Pr
1−x
Ca
x
MnO
3
(x = 0.2–0.95)
reveals that S
M
can show a complex behavior and a change
of sign with temperature depending on hole content (x ).
Nair and Banerjee [12] found that S
M
decreases with the
weakening of charge ordering in Pr
0.5
Ca
0.5
Mn
1−x
Al
x
O
3
(x = 0–0.1). In the Nd
0.5
Ca
0.5
MnO
3
system, the study re-
ported by Karmakar et al. [13] reveals a magnetic entropy
change of +3.4 J kg
−1
K
−1
(under H = 6 T) just below