A8: Multiferroic 0–3, 2–2, and 1–3 composites
Magnetoelectric coupling phenomena in heterogeneous oxide systems can be affected by the chemical composition of the respective components, their crystal structure and the size and quality of the interface. The variation of these parameters therefore leads to a deeper understanding of the underlying coupling mechanisms.
In the project A8 composite multiferroics of different dimensionality are synthesized and characterized with respect to their structure and magnetoelectric coupling. As ferroelectric component pure and cation-substituted BaTiO3 is applied. The magnetic components are either ferrite-spinels AFe2O4 (A = Mg, Mn, Co, Ni, Cu) or double perovskites of the type A2FeMoO6 (A = Ca, Sr, Ba) and A2CrWO6 (A = Ca, Sr, Ba). By chemical substitution the individual ordering temperatures will be tailored, putting special emphasis on the influence of the crystal structure (e.g. lattice strain, cation ordering).
In addition to the chemical composition also the dimensionality of the involved oxides and in turn of their interfaces will be varied by synthesis of heterostructures (composites) with different dimensionality: 0–3-composites are prepared from core-shell-particles of well-defined size and shape, the sintering of which leads to dense ceramics. Layered 2–2-composites are fabricated by spin coating, tape casting or doctor blading of precursor compounds, which in a succeeding step are reacted to the corresponding oxides. Furthermore, single crystals of the magnetic and ferroelectric materials will be grown by the floating zone and the Czochralski-technique and used for the epitaxial growth of the second component by PLD. For 1–3-heterostructures the highly ordered pores of porous Al2O3-membranes or mesoporous silicates will be applied as hard templates.
For the structural characterization of the obtained samples powder and single crystal X-ray diffraction, neutron diffraction, as well as EXAFS and transmission electron microscopy are used. The chemical composition is analyzed via EDX and XRF. Valence states of redox active transition metals are determined by XANES. Finally, the magnetic and (di‑) electric properties of the samples and the magnetoelectric coupling phenomena are studied in detail at different magnetic fields and temperatures.
Principal Investigators
|
Prof. Dr. Stefan Ebbinghaus ⇒
stefan.ebbinghaus@chemie.uni-halle.de phone: +49 (0) 345/55 25870 fax: +49 (0) 345/55 27343 |
|
|
Prof. Dr. Dietrich Hesse ⇒
phone: +49 (0) 345/55 82741 fax: +49 (0) 345/55 11223 |
|