Elastic behaviour of Microstructures Wilfried Schranz, Andriy Kityk* and Andreas Tröster

1. Elastic behaviour of Microstructures Wilfried Schranz, Andriy Kityk* and Andreas Tröster Institut für Experimentalphysik, Universität Wien Strudlhofgasse 4, 1090 Wien *Institute of Computer Science, Faculty of Electrical Engineering, Technical University of Czestochowa, Al. Armii Krajowej 17, 42-200, Czestochowa, Poland Abstract Real materials contain very often a number of different microstructures. Examples are: -          Domains and domain walls in ferroic crystals -          Discommensurations in incommensurate systems -          Phase fronts, precursor cluster, etc. near phase transformations -          Flux lines near superconductors…… We show on various examples how these microstructures influence the macroscopic elastic properties of crystals. • Experimental Results • Domain wall motion in SrTiO33 Experimental techniques Fig.3:Stress dependence of the elastic constants of SrTiO3. Suppression of domain wall motion due to static stress. • Domain freezing in KMn1-xCaxF34 Fig. 1 Fig.2 Ultrasonic wave probes an inhomogenous medium (Phase transition cluster)1,2 Dynamic mechanical Analysis in Parallel Plate (PP) and Three Point Bending (TPB) geometry Fig.4:Temperature dependence of the domain wall induced elastic softening at various frequencies shows the ultralow frequency domain wall dynamics. • Ultralow frequency elastic relaxation in the • quantum paraelectric state of SrTiO35 • Pinning of domain walls on random defects leads to logarithmic • dispersion4 (Nattermann, et al. PRL 87, 2001) Fig.5: Frequency scan at different temperatures displays the logarithmic dispersion far away from the domain freezing transition. Fig.6:Temperture dependence of the real and imaginary part of the complex elastic constant of SrTiO3 at various static loads. Low frequency Dispersion in KSCN Due to heat diffusion Dynamics6 Fig.7: Real and Imaginary part of the Dynamic elastic Susceptibility of KSCN. References 1W. Schranz, D. Havlik, PRL 73, 2575 (1994) 2A. Tröster, W. Schranz, G. Krexner, et al. PRL 85, 2765 (2000) 3A.V. Kityk, W. Schranz, et al. Phys. Rev. B61, 946 (2000) 4W. Schranz, A. Tröster, et al. Europhys. Lett., submitted 5A.V. Kityk, W. Schranz, et al. Europhys. Lett. 50, 41 (2000) 6A.Tröster and W. Schranz, Phys. Rev. B, submitted Acknowledgements: The work was supported by FWF project No P15016