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Weiche Materie Poster: Do., 13:00–15:30 D-P325
Thin Films of Multiferroic Oxides
Christophe Daumont 1 , Gustau Catalan 1,2 , Oliver Seeck 3 , Wolgang
Caliebe 3 , Beatriz Noheda 1
1 Solid State Chemistry, Material Science Centre, University of Groningen, Nijemborgh
4, 9747 AG Groningen, The Netherlands – 2 Departement of Earth Sciences, University
of Cambridge, Dowing Street, Cambridge, CB2 3EQ, United Kingdom – 3 HASYLAB-
DESY, Notkestr. 85, D-22603 Hamburg, Germany
Multiferroics are materials that exhibit ferroelectricity and magnetism simultaneously.
If these two properties are coupled, multiferroics offer the interesting possibility of
manipulating electric properties by applying a magnetic field and vice versa, with
potentially high impact in spintronics, memory, sensor, and other applications. Unfortunately,
they are very rare and the existing ones only show large magnetoelectric
(ME) coupling at low temperature. Although the search and design of new multiferroics
are attracting much attention since the last couple of years, the mechanisms
driving the coupling between ferroelectricity and magnetism are very diverse and still
not well understood [1]. Among the multiferroics, the perovskite oxides are of great interest
because their relatively simple structure allows easier access to the fundamental
understanding of their ME coupling.
Epitaxial growth of multiferroic films allows the tuning of the film properties, by
means of strain imposed by the substrate. So strain provides an additional parameter
to increase the temperature and magnitude of the ME coupling. Perovskites are well
suited for that due to the availability of several perovskite substrates, such as SrTiO3.
Using Pulsed Laser Deposition (PLD), multiferroic BiFeO3 and TbMnO3 films with
thicknesses of tens of nanometers have been epitaxially grown on SrTiO3 substrates
[2],[3]. More recently, ultrathin films of BiFeO3 have also been reported down to 5nm[4],
but the characterization of such thin layers by means of standard x-ray diffraction is
not easy because of the limited diffracted intensity. As far as we know, there are no
reports of TbMnO3 films with thicknesses below 100 nm. Growth and characterization
of ultrathin film is also important in the context of multilayer growth.
We report the successful growth of epitaxial ultrathin (5 nm) films of BiFeO3 and
TbMnO3 on SrTiO3 single crystals via RHEED-assisted PLD. The structural characterization
of these films has been done using synchrotron radiation at the DORIS W1
beamline at HASYLAB in grazing-incidence and reflection geometry. By characterizing
these films as a function of temperature and thickness we expect to shed light into
the effect of strain and the strain relaxation on the multiferroic properties of the layers.
[1] N. M. Fiebig, J. Phys. D, R123 (2005); [2] J. Wang et al., Science 299, 1719
(2003); W. Eerenstein et al., Science 307, 1203 (205); [3] Y. M. Cui et al., APL 86,
203501 (2005) ; G. Xu et al., APL 86, 182905 (2005) ; X. Qi et al., APL 86, 071913
(2005); [4] H. Béa et al., APL 88, 062502 (2006)