Session K20 - Poster Session.
POSTER session, Sunday afternoon, April 29
Congressional C, Renaissance Hotel
The characteristic feature of ferroic crystals - a polydomain structure - allows one by suitable driving forces to produce domain configurations exhibiting a symmetry on a macroscopic scale. Properties of such processed ferroic crystals can be highly specific; under certain circumstances their domain configurations can be relatively stable. A particular example represent engineered rhombohedral single crystals of relaxor based ferroelectric Pb(Zn_1/3Nb_2/3)O_3-PbTiO_3 which are reported to have much enhanced piezoelectric and dielectric properties and to be almost fatigue-free. These phenomena are probably related to the supposed macroscopic symmetry \mathsf4mm. However, the actual domain structure has not been fully analyzed yet. We demonstrate a theoretical method how to derive possible coherent domain configurations, i.e. those configurations that are macroscopically symmetric and involve all domain states belonging to a single orbit of the respective point group. Such states will have equal free energy in an external field invariant under the point group. As an illustration, we give results for some multiferroic materials. Also, we determine driving forces that can induce coherent domain configurations.