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DF: Dielektrische Festkörper
DF 11: Electric, Electromechanical and Optical Properties II
DF 11.1: Invited Talk
Friday, March 31, 2006, 10:50–11:30, M{\"U}L Elch
Universal domain wall dynamics in ferroics and relaxors — •Wolfgang Kleemann — Angewandte Physik, Universität Duisburg-Essen, Duisburg, Germany
Domain walls in random ferroic media reveal different dynamic modes. The complete series under external ac fields at decreasing frequencies, f, segmental relaxation, creep, slide and switching, is observed in quantum ferroelectric SrTi18O3 [1], superferromagnetic CoFe/Al2O3 multilayers [2], and ultrathin ferromagnetic trilayers Pt/Co/Pt [3]. Dynamic scaling explains the transition from Cole-Cole-type segmental relaxation to creep with inverse power law dispersion as observed in periodically-poled KTiOPO4 at fm = fm0exp(- E/kBT), fm0 = 3× 109 Hz and E = 0.6 eV [4]. Segmental relaxation and creep are also observed in the uniaxial relaxor Sr0.61Ba0.39Nb2O6 [5], where wall pinning due to charge disorder-induced random electric fields is also responsible for the occurrence of nanopolar regions in the paraelectric regime, T > Tc ≈ 350 K. Their interfaces with the paraelectric environment reveal similar dynamic modes as pinned ferroic domain walls. [1] J. Dec et al., Ferroelectrics 298 (2004) 163. [2] X. Chen et al., Phys. Rev. Lett. 89 (2002) 137023. [3] O. Petracic et al., unpublished. [4] Th. Braun et al., Phys. Rev. Lett. 94 (2005) 117601. [5] W. Kleemann et al., Phys. Rev. B 65 (2002) 220101.