Elastic behaviour of Microstructures 

Wilfried Schranz, Andriy Kityk* and Andreas TrösterInstitut 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

 

AbstractReal 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 techniques

Experimental Results

• Domain wall motion in SrTiO33

Fig. 1

Ultrasonic wave probes an inhomogenous medium (Phase transition cluster)1,2

Fig.2

Dynamic mechanical Analysis in Parallel Plate (PP) and Three Point Bending (TPB) geometry

Fig.3: Stress dependence of the elastic constants of SrTiO3.Suppression of domain wall motion due to static stress.

•Domain freezing in KMn1-xCaxF34

References1 W. Schranz, D. Havlik, PRL 73, 2575 (1994)2 A. Tröster, W. Schranz, G. Krexner, et al. PRL 85, 2765 (2000)3 A.V. Kityk, W. Schranz, et al. Phys. Rev. B61, 946 (2000)4 W. Schranz, A. Tröster, et al. Europhys. Lett., submitted5 A.V. Kityk, W. Schranz, et al. Europhys. Lett. 50, 41 (2000)6 A.Tröster and W. Schranz, Phys. Rev. B, submitted

Acknowledgements: The work was supported by FWF project No P15016

•Pinning of domain walls on random defects leads to logarithmic dispersion4 (Nattermann, et al. PRL 87, 2001)

Fig.6: Temperture dependence of the real and imaginary part of the complex elastic constant of SrTiO3 at various static loads.

Fig.5: Frequency scan at different temperatures displays the logarithmic dispersion far away from the domain freezing transition.

• Ultralow frequency elastic relaxation in the quantum paraelectric state of SrTiO3

5

Fig.4: Temperature dependence of the domain wall induced elastic softening at various frequencies shows theultralow frequency domain wall dynamics.

Low frequencyDispersion inKSCNDue to heat diffusion Dynamics6

Fig.7: Real and Imaginary part of theDynamic elastic Susceptibility of KSCN.