Public Physic Colloquium in the Winter Terms 2009/2010 in Münster
Place:     Germany, 48149 Münster, Wilhelm-Klemm-Str. 10, IG I, HS 2
Time:     Thursday, 22.10.2009  16:00 h c.t.
Colloquium Coffee at 15:45 h  at the Lecture Hall

Nanoscale ferroelectric and multiferroic oxide heterostructures
Prof. Dr. Dietrich Hesse, Max-Planck-Institut für Mikrostrukturphysik, Halle

Nanoscale ferroelectric and multiferroic epitaxial oxide heterostructures are promising for a number of applications like high-density non-volatile memories or sensors which can react on both magnetic and electric fields. And they are an intriguing solid state physics playground. We prepare nanostructured arrays and superlattices from epitaxial ferroelectric and magnetic oxides like ferroelectric Pb(Zr,Ti)O₃ (PZT), antiferroelectric PbZrO₃, or the magnetic perovskites (La,Sr)MnO₃ or SrRuO₃ by pulsed laser deposition. Microstructure-property relations, size effects, and the influence of strain are investigated using XRD, (HR)TEM, EDX, AFM, magnetic and piezoresponse force microscopy (MFM, PFM), and macroscopic ferroelectric and magnetic measurements (the latter in cooperation with M. Ziese, Leipzig).
The physical properties of large-area epitaxial Pt/PZT/Pt nanocapacitor arrays of 60 nm pitch prove to be suitable for high-density (Tbit/inch² range) non-volatile ferroelectric memories. Their favourable switching properties are enabled by the ferroelectric domain structure and the properties of the domain boundaries. Superlattices show surprising property changes in dependence on the thickness of the individual layers and on strain, among them, e.g., layer thickness-dependent structural phase transitions. In (La,Sr)MnO₃/SrRuO₃ superlattices, antiferromagnetic coupling depends on intimate interfacial contact and interdiffusion on the nanometer scale.