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Theoretically predicted ferroelectric phase induced by tensile stress was confirmed in SrTiO3 epitaxial films and SrTiO3/DyScO3 heterostructures on DyScO3 substrates, prepared in top world laboratories. It is driven near 270 K by a soft phonon mode in the THz range which in the whole measured temperature region of 20-300 K couples to an overdamped excitation of order-of-magnitude lower frequency (obviously of strong anharmonic origin) and is tunable by electric field. Celý text >>
We have investigated the magnetoelectric effect in BiFeO3 and observed rather a large change of permittivity with magnetic field at high temperatures, where the sample becomes partially conducting due to defects. However, in this case the magnetoelectric effect is not intrinsic, i.e. due to coupling of polarization and magnetization, but due to combination of magnetoresistance and Maxwell-Wagner polarization effect (see S. Kamba et al., Phys. Rev. B 75, 024403 (2007)). Celý text >>
Computer simulations based on Ginzburg-Landau-Devonshire theory are used to investigate piezoelectric response of tetragonal BaTiO3 crystals. We have shown that piezoelectric response of twinned BaTiO3 increases with increasing density of 90° domain walls. A considerable enhancement of the longitudinal piezoelectric coefficient is predicted for domain sizes below 50 nm. Celý text >>
Series of 15 new liquid crystalline compounds have been synthesized and studied composed of non-symmetrical bent-shaped molecules based on a 7-hydroxynaphtalene-2-carboxylic acid, the central naphtalene core being laterally substituted by chlorine or the methyl group. Studies of textures in planar samples, calorimetric study, X-ray diffraction and dielectric measurements enabled to establish mesomorphic properties (ie. phase transitions and sequences of phases) of these compounds. The studied compounds exhibit the antiferroelectric B2 phase and relatively scarce polar columnar phases. Celý text >>
A new series of new multifunctional materials with the azo-group in the molecular core has been prepared, which exhibit ferroelectric properties and are photosensitive. With these materials (known as photoferroelectrics) the illumination by visible light can change their electric and optical properties. After the light is switched off their properties are restored to the original state. Such materials offer a series of applications in optoelectronics or photonics. Celý text >>
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