University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Thursday, November 20th 2014
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: A. P. Levanyuk, Department of Physics, University of Washington, Seattle
Subject: Phase Transitions and Domain Structures in Thin Ferroelectric Films and Multilayers

Recent advances in technology made available thin ferroelectric films and ferroelectric-paraelectric multilayers of very high quality. At the same time our understanding of properties of these systems is far from being complete. This is evidenced, in particular, by difficulties in interpretation of various anomalies observed at ferroelectric phase transitions in these systems. Experimentally, they are different from the phase transition anomalies in high quality bulk systems but the reasons of the differences are debatable. The aim of the talk is to discuss some specific features of ferroelectric phase transitions in thin films and multilayers which are visible now but, to a considerable extent, are not fully taken into account by the existing theory. The discussion is limited to answering the question about character of the ferroelectric state forming just after the transition. Three possibilities are considered: single-domain, multi-domain, two-phase. First, thin films with electrodes and on a substrate will be discussed. Incomplete screening of the depolarizing field in the electrodes and difference in properties of the surface layer and the bulk implies formation of domains at the phase transition for realistic parameters of the system. Clamping by the substrate may lead also to formation of two-phase state. This phenomenon is practically unexplored for thin films on substrates. Second, ferroelectric-paraelectric multilayers will be discussed which prove to be much more challenging for theoretical study than the thin films. This is because of lack of periodicity in the polarization distribution despite of periodicity of the structure.

Faculty Host: Boris Shklovskii

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