Dresden 2017 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 15: Ferroics - Domains, Domain Walls and Skyrmions III

DF 15.2: Vortrag

Mittwoch, 22. März 2017, 15:30–15:45, WIL B321

Probing polar order in improper ferroelectric thin films using SHG — •Johanna Nordlander¹, Gabriele De Luca¹, Marta D. Rossell², Manfred Fiebig¹, and Morgan Trassin¹ — ¹Departments of Materials, ETH Zürich, Switzerland — ²Electron Microscopy Center, EMPA, Switzerland

Improper ferroelectrics are materials whose ferroelectricity is driven by a non-polar order parameter. This type of ferroelectricity can lead to exotic properties which do not exist in standard ferroelectrics. For example, improper ferroelectricity in hexagonal YMnO₃ (YMO), which is geometrically driven through a lattice trimerization, leads to a topological domain vortex pattern. There has been a revival in the growth of improper ferroelectric thin films, and these bulk-like ferroelectric domain vortices were also reported in YMO thin epitaxial layers. In order to understand the behavior of ultrathin YMO, and in particular in order to investigate the influence of epitaxial strain on the ferroelectric trimerization, we use optical second harmonic generation (SHG) to non-invasively probe the ferroic state of these thin films for different epitaxial growth conditions. Here, we demonstrate the growth of highly oriented, epitaxial hexagonal YMO thin films by pulsed laser deposition on various substrates. We report reversible scanning-probe-tip-induced ferroelectric switching and the subsequent spatially resolved SHG analysis. The temperature-dependent emergence of the coexisting magnetic and electric orders is investigated by SHG. Ultimately, we provide a deeper insight into the mechanism of ferroelectric domain vortex formation and antiferromagnetism in thin film YMO.