Dresden 2003 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 6: Keramiken, Gradientenwerkstoffe und Relaxoren
DF 6.6: Vortrag
Mittwoch, 26. März 2003, 16:30–16:50, HSZ/403
Domain states in uniaxial relaxors and quantum ferroelectrics — •Wolfgang Kleemann1, Jan Dec2, Ruiping Wang3, Mitsuru Itoh4, and Robert Pankrath5 — 1Laboratorium für Angewandte Physik, Gerhard-Mercator-Universität, Duisburg — 2Institute of Physics, University of Silesia, Katowice, Poland — 3Smart Materials Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan — 4Materials & Structures Laboratory, Tokyo Institute of Technology, Yokohama, Japan — 5Fachbereich Physik, Universität Osnabrück
Non-Debye relaxation processes are observed in the random-field induced ferroelectric domain state of the uniaxial solid solution strontium barium niobate (SBN). Because of its inherent quenched charge disorder this system is probably the most perfect materialization of the three-dimensional ferroic random-field Ising model (RFIM). It shows modified critical and drastically slowed-down dynamic behavior. While polydispersive relaxation of pinned domain wall segments characterizes the rf regime, creep of the domain walls gives rise to Curie-von Schweidler (CvS) type very low-frequency (vlf) dispersion of the complex susceptibility. The CvS exponent is shown to vary drastically when reducing the domain wall density. A dynamic phase transition, where the order parameter Q=(ω /2π)∮Pdt changes from Q= 0 (rf) to Q≠ 0 (vlf), separates both dispersion regimes. Similar processes are observed in the quantum ferroelectric SrTi18O3. Its domain state is attributed to pinning by quenched defects, which are produced during the exchange of the oxygen isotopes, 16O→ 18O.