A2: Polarization interaction in wurtzite-perovskite-spinel heterostructures grown by laser-MBE
The project investigates experimentally the polarization coupling, and magnetic and multiferroic coupling in multilayered thin film structures, and in multiphase composites which consist of piezoelectric semiconductors (ZnO), perovskite ferroelectrics (BaTiO3), and ferrimagnetic spinels (Zn,Ni,Co)Fe2O4, and multiferroic oxides.
Experience gained from experimentally investigated and modeled asymmetric polarization hysteresis effects in single-, double- and triple-layer structures of ZnO and BaTiO3 will be applied to
(a) The inclusion of magnetic components as for example the above mentioned spinels into the ZnO-BaTiO3 heterostructures, in order to control the ferro- and piezoelectric polarization by magnetic fields; and
(b) Magnetic and multiferroic coupling effects at planar film interfaces and granular composite interfaces of ferrimagnetic spinels (Zn,Ni,Co)Fe2O4 and ferroelectrics such as BaTiO3. First composites deposited from homogeneous mixtures of ZnFe2O4 und BaTiO3 show systematic and reproducible field shifts of the magnetic hysteresis. These shifts were identified as exchange bias effects in cooperation with the projects B1 and B5.
The ferroelectric, magnetic and multiferroic properties of the heterostructures (a) and (b) are investigated now in more detail using a new ferroelectric and multiferroic thin film analyzer system. A new subject is the doping of multiferroic structures.
In addition, A2 will prepare all ZnO-BaTiO3-based thin film structures for optical and electrooptic investigations in project B3, different ZnO-based field effect transistors with ferroelectric / magnetic / multiferroic gate oxide for B4, and magnetic tunnel junctions and spin filters with spinel films for B6. The control of epitaxial growth in the laser-MBE system with in-situ RHEED will be further extended by in-situ spectroscopic ellipsometry (B3), which has to be considered as a unique methodical extension.
Principal Investigator
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Prof. Dr. Michael Lorenz ⇒
phone: +49 (0) 341/97 32661 fax: +49 (0) 341/97 39286 |
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