J Supercond Nov Magn
DOI 10.1007/s10948-012-1955-9
ORIGINAL PAPER
Effect of Air Annealing on the Structural and Magnetic Properties
of LaMnO
3
Perovskite Produced by Reactive Spark Plasma
Sintering Route
Y. Regaieg · G. Delaizir · L. Sicard · J. Monnier ·
F. Herbst · B. Villeroy · C. Godart · M. Koubaa ·
A. Cheikhrouhou · S. Ammar-Merah
Received: 27 November 2012 / Accepted: 1 December 2012
© Springer Science+Business Media New York 2013
Abstract Perovskite-type lanthanum manganite (LaMnO
3
)
was synthesized from Mn
2
O
3
and La
2
O
3
precursor powders
using the Spark Plasma Sintering technique (SPS). The in
situ reaction proceeds in a few minutes at 1000 °C under
50 MPa with a very high heating rate of 100 °C/min. The
Rietveld refinement of the X-ray powder diffraction shows
that LaMnO
3
sample crystallizes in a perovskite structure
of O
′
-type orthorhombic symmetry with Pbnm space group.
After annealing at 1000 °C in air for 10 hrs, the symme-
try changes to rhombohedral with R-3c space group. For the
as prepared sample, two critical temperature points in the
temperature dependence of the ZFC and FC magnetization
occurring at 125 K and 145 K are observed. They are sug-
gested to be related to A-type antiferromagnetic Néel tem-
perature and ferromagnetic short range order, respectively.
The ferromagnetic component in the annealed sample in-
creases indicating the expected variation in the concentra-
tion of Mn
3+
and Mn
4+
ions, which was attributed to the
oxygen stoichiometry effects.
Keywords Spark Plasma Sintering · Manganese oxides ·
Synthesis · Magnetic behavior
Y. Regaieg · L. Sicard · F. Herbst · S. Ammar-Merah ( )
ITODYS, Université Paris Diderot, CNRS UMR 7086, 15 rue
Jean Antoine de Baïf 75205 Paris, France
e-mail: ammarmer@univ-paris-diderot.fr
Y. Regaieg · M. Koubaa · A. Cheikhrouhou
LPM, Faculté des Sciences de Sfax, B.P. 1171, 3000 Sfax, Tunisia
G. Delaizir · J. Monnier · B. Villeroy · C. Godart
ICMPE, Université Paris Est Creteil, CNRS UMR 7182, 2 rue
Henri Dunant, 94320 Thiais, France
1 Introduction
The undoped stoichiometric LaMnO
3
compound, contain-
ing only Mn
3+
ions, is an insulating antiferromagnet with
an A type structure (antiferromagnetic stacking of ferro-
magnetic planes) [1]. Doping with divalent cations oxidizes
Mn
3+
into Mn
4+
, introducing holes in the d band. The pres-
ence of a mixed valence manganese state is critical for the
existence of both high conductivity and ferromagnetism. In
these materials, the correlation between magnetic and trans-
port properties has been usually interpreted based on the
double exchange (DE) mechanism, the super-exchange (SE)
interactions, the electron–phonon coupling due to the Jahn–
Teller effect of Mn
3+
ions and the magnetic-phase sepa-
ration [2–5]. The Spark Plasma Sintering (SPS) technique
is well known to allow sintering of materials and multi-
materials (e.g., graded materials) in a few minutes with a
high compactness. It is a non-conventional sintering tech-
nique based on the use of pulsed current, enabling fast heat-
ing and cooling rates, and lower sintering temperatures are
often observed in comparison with conventional sintering
techniques. The interest of the scientific community for this
technique grows rapidly for its great advantages namely, the
gain of time, the improved properties of the sintered ceram-
ics and the ease of transfer to industry; it also appeared re-
cently that SPS is a new technique to achieve very fast solid
state chemistry [6, 7]. In this paper, we report on the synthe-
sis of highly dense and fine grained LaMnO
3
ceramic using
reactive SPS route and the effect of annealing treatment on
its structural and magnetic properties.
2 Experimental Procedure
The raw materials, La
2
O
3
(Alfa Aesar, 99.9 %) and Mn
2
O
3
(Alfa Aesar, 98 %), were mixed in an oscillating milling