Superlattices of Metallic Ferromagnetic Oxides:
Interface Antiferromagnetic Coupling Effect
Bhaskar Chandra Behera1, Venkata Ravindra A1, Prahallad Padhan1*, Wilfried Prellier2
1
2
Department of Physics, Indian Institute of Technology Madras, Chennai-600036, India
Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd du Marechal Juin, F-14050 Caen Cedex, France
*
Corresponding author’s e-mail: padhan@iitm.ac.in
Abstract
Raman spectra and x-ray diffraction of the superlattices
consisting of La0.7Sr0.3MnO3 (LSMO) and SrRuO3 (SRO)
reveal orthorhombic structure of spacer layer LSMO and
the presence of in-plane compressive strain, respectively.
Magnetic measurements reveal enhanced coercivity,
reduced magnetization, and switching of magnetic
coupling with the magnetic field orientations. These
magnetic properties are explained by the observed
orthorhombic structure of spacer LSMO in Raman
scattering.
Keywords: Superlattice, Pulsed laser deposition,
antiferromagnetic coupling, orthorhombic structures.
Introduction
The multilayers of two metallic ferromagnetic oxides
LSMO and SRO exhibit several interesting magnetic
properties such as exchange bias effect, inverted
hysteresis loop, antiferromagnetic coupling switches to
ferromagnetic coupling by changing the orientation of
field etc. [1, 2]. So far, the attention has been mainly on
the (001)-oriented LSMO/SRO superlattices, probably
due to the simplicity of growth. However, the
enhancement of magnetic properties observed for the
(110) orientation LSMO and SRO thin films compared
to (001) orientation due to the less crystal deformation,
the more compact layer stacking therefore stronger
interlayer spin-spin interaction, the faster and
anisotropic relaxed unit cells, and the quenching of
polar discontinuity [3, 4]. We have grown (110)
oriented SRO/LSMO superlattices using multi-target
pulsed laser deposition technique and studied their
crystal and electronic structures and magnetic
properties.
Results and Discussions
The x-ray diffraction patterns show the several
satellite reflections apart from the substrate (110) STO
peak confirms the long range periodicity of the
superlattice structure with good crystallinity, shown in
Figure 1. The observed out-of-plane lattice parameter of
these superlattice is relatively larger compared to the
bulk SRO value, indicating the presence of in-plane
compressive strain due to the lattice mismatch of STO
with bottom layer SRO. Raman spectra (not shown
here) of these superlattices show the orthorhombic
structure rather than expected rhombohedral structure
for less than 4 u.c. thick LSMO spacer.
Fig1: The -2 x-ray diffraction profiles and simulated spectra
of (a) (110)STO/[14-u.c. SRO/2-u.c. LSMO]x15 and (b)
(110)STO/[14-u.c. SRO/4-u.c. LSMO]x15 superlattices. The
(110) Bragg’s reflection of STO as well as the satellite peaks
are indicated.
The temperature dependent magnetization curves
M(T) show the in-plane antiferromagnetic coupling and
out-of-plane ferromagnetic coupling between the SRO
and LSMO layers of these superlattices below 160 K,
the Tc of SRO. The field dependent magnetization
curves (not shown here) measured at 10 K reveal the
enhanced coercivity, reduced magnetization. These
magnetic properties changes because of the observed
orthorhombic structure of spacer LSMO layer in
SRO/LSMO superlattice from the Raman scattering.
Figure 2: Temperature dependent 0.1 T field cooled (a) inplane magnetization and (b) out-of-plane magnetization of the
superlattices with n = 2 and 4.
References
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Lett. 88, (2006) 192509.
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Espinos, Phys. Rev. B76, (2007) 224415.
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