Investigation of biferroic properties in
La
0.6
Sr
0.4
MnO
3
/0.7Pb„Mg
1/3
Nb
2/3
…O
3
–0.3PbTiO
3
epitaxial bilayered
heterostructures
Ayan Roy Chaudhuri,
1,a͒
S. B. Krupanidhi,
1,b͒
P. Mandal,
2
and A. Sundaresan
2
1
Materials Research Centre, Indian Institute of Science, Bangalore 560 012, India
2
Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research,
Jakkur, Bangalore 560 064, India
͑Received 13 May 2009; accepted 23 July 2009; published online 2 September 2009͒
Epitaxial bilayered thin films consisting of La
0.6
Sr
0.4
MnO
3
͑LSMO͒ and
0.7Pb͑Mg
1/3
Nb
2/3
͒O
3
–0.3PbTiO
3
͑PMN-PT͒ layers of relatively different thicknesses were
fabricated on LaNiO
3
coated LaAlO
3
͑100͒ single crystal substrates by pulsed laser ablation
technique. The crystallinity, ferroelectric, ferromagnetic, and magnetodielectric properties have
been studied for all the bilayered heterostructures. Their microstructural analysis suggested possible
Stranski–Krastanov type of growth mechanism in the present case. Ferroelectric and ferromagnetic
characteristics of these bilayered heterostructures over a wide range of temperatures confirmed their
biferroic nature. The magnetization and ferroelectric polarization of the bilayered heterostructures
were enhanced with increasing PMN-PT layer thickness owing to the effect of lattice strain. In
addition, evolution of the ferroelectric and ferromagnetic properties of these heterostructures with
changing thicknesses of the PMN-PT and LSMO layers indicated possible influence of several
interfacial effects such as space charge, depolarization field, domain wall pinning, and spin disorder
on the observed properties. Dielectric properties of these heterostructures studied over a wide range
of temperatures under different magnetic field strengths suggested a possible role of elastic strain
mediated magnetoelectric coupling behind the observed magnetodielectric effect in addition to the
influence of rearrangement of the interfacial charge carriers under an applied magnetic field. © 2009
American Institute of Physics. ͓doi:10.1063/1.3211315͔
I. INTRODUCTION
Multiferroic materials ͑MFs͒ with coexisting ferroelec-
tricity and magnetism have enjoyed flurry of studies in recent
years due to fundamental scientific interest and significant
technological promises for their potential applications in fu-
ture generation microelectronic devices, such as sensors,
transducers, and memory devices. The coexistence of ferro-
electric ͑FE͒ and ferromagnetic ͑FM͒ properties in MFs and
a coupling between them have been predicted to be useful in
designing novel devices with parametric values and
flexibility.
1
But the scarcity of single phase intrinsic MFs
combined with their very feeble magnetoelectric ͑ME͒ re-
sponse at room temperature ͑RT͒ have resulted in the real-
ization of such multifunctional devices hitherto unachieved.
The zest for understanding the mechanism of MF coupling
and achieving substantial ME response have intrigued re-
searchers worldwide toward alternative approaches to syn-
thesize artificial ME MFs. Various approaches have been
made to design and synthesize artificial multiferroic struc-
tures. One of them is doping either a magnetic impurity in a
FE host or a FE impurity in a magnetic host or designing
composites with FE and FM hosts. Various bulk ME com-
posites have been developed consisting of a FE constituent
͓e.g., BaTiO
3
͑BT͒ and Pb͑Zr
x
Ti
1−x
͒O
3
͑PZT͔͒ andaFM
constituent ͓e.g., CoFe
2
O
4
͑CFO͒, NiFe
2
O
4
͑NFO͒, and
Terfenol-D͔. In the BT/CFO bulk composite, the magnetic
field induced dielectric response surpassed the values ob-
tained from any single phase MF material by one order of
magnitude.
2,3
The ME behavior of such bulk composites gen-
erally depends on their microstructure and the coupling
across the interface of the FE and the FM constituents.
4,5
More recently attention has been given to bilayers and mul-
tilayers of such composites where the induced ME effect
arises as the product property of a magnetostrictive and a
piezoelectric compound. These layered composites are espe-
cially promising due to their low leakage current and supe-
rior poling properties.
6–8
However, such layered composite
materials also suffer from several limitations such as poor
mechanical coupling between layers due to nonepitaxial na-
ture of the interfaces, impurities arising from interfacial ion
diffusion, lack of scaling possibilities, etc. To overcome
these difficulties involved with the bulk or layered compos-
ites, significant efforts have been devoted in designing ME
nanostructures since these engineered structures, especially
ME thin films, can easily undergo on-chip integration in mi-
croelectronic devices. The bilayers, superlattices, and nano-
composite thin film heterostructures combining FE and FM
phases might have stronger feasibilities to overcome the dif-
ficulties associated with the bulk materials. These hetero-
structures have also exhibited stronger RT ME coupling
compared to the single phase MFs.
9,10
While the superlattice
approach has been investigated in great detail with different
a͒
Electronic mail: ayan@mrc.iisc.ernet.in.
b͒
Author to whom correspondence should be addressed. FAX: ϩ9180 2360
7316. Electronic mail: sbk@mrc.iisc.ernet.in.
JOURNAL OF APPLIED PHYSICS 106, 054103 ͑2009͒
0021-8979/2009/106͑5͒/054103/8/$25.00 © 2009 American Institute of Physics106, 054103-1