Browsing by Author "Fousek, Jan"
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- ItemCrystal physics of ferroics at its best: A tribute to professor Hans Schmid(1997) Fousek, JanThe proceedings of MEIPIC-3 is surely the appropriate forum to pay tribute to Professor Hans Schmid of the University of Geneva, on the occasion of his 65th birthday; in a sense a tribute of a child to the father since it was he who established this series of conferences and since its topic is surely not showing any marks of aging.
- ItemDomain formation in thin ferroelectric films: The role of depolarization energy(1997) Kopal, Antonín; Bahník, Tomáš; Fousek, JanFormulae for equlibrium stripe domain width Weq in a nonductive ferroelectric plate of thickness d are deduced, taking into account electrostatic interaction of surfaces. It is shown that the classical formula giving W eq ∞ d 1/2 is not applicable when the sample thickness decreases below the value dcrit which is a function of dielectric properties and domain wall energy density. For many ferroelectrics the value of dcrit lies in a range which can be easily reached far below the transition point by contemporary thin film techniques; it further increases as the transition point is approached. In the region d < dcrit the width Weq increases with decreasing d. For samples with thickness d << dcrit the domain structure becomes insensitive to electrical boundary conditions and will be primarily determined by other factors.
- ItemDomain phenomena in single crystalline and ceramic ferroics: Unresolved and attractive problems(Technická Univerzita v Liberci, 2003) Fousek, Jan; Cross, Leslie Eric; Nosek, JaroslavDomain-related properties of ferroic materials offer a number of application aspects. However, some of the involved domain characteristics have not been fully explained and may initiate an interesting field of further research. Here we specify and discuss several such still unresolved problems related to single crystalline and ceramic samples. Those concerning static domain pattern include the topic of domain wall thickness and of possible macroscopic wall properties, macroscopic properties of ceramic samples depoled in different ways and application of multidomain systems in surface acoustic wave devices. Discussed problems related to dynamic domain phenomena include the issue of visibility and thickness of moving domain walls, the effect of nucleation and the topic of extrinsic contributions to macroscopic properties of multidomain samples. © 2002 Elsevier Science B.V. All rights reserved.
- ItemDynamics of polarization reversal in purified Rb2ZnCl4(1997) Hauke, Tilo; Müller, Volkmar; Beige, Horst; Fousek, JanThe dynamics of polarization reversal in sinusoidal fields (0. 1Hz≤f≤50kHz) was studied in the ferroelectric lock-in phase of purified Rb2ZnCl4 crystals. The frequency dependence of remanent polarization and coercive field Ec is qualitatively the same above and below T*≈160K, where for all measuring frequencies Ec starts to increase rapidly with decreasing temperature. A model which treats sideways shifts of planar, nearly regularly arranged domain walls as the only mechanism of polarization reversal in Rb2ZnCl4 is applicable for the quantitative description of ferroelectric hysteresis loops in the whole temperature interval under investigation. The anomalous increase of Ec at T* seems to be connected to a corresponding increase of the viscosity coefficient.
- ItemElastic properties of purified [N(CH3)4]2CuCl4 crystals near the ferroelastic lock-in transition(1996) Müller, Volkmar; Fuith, Armin H.; Fousek, Jan; Warhanek, Hans; Beige, HorstThe low frequency elastic properties of ferroelastic [N(CH3)4]2CuCl4 crystals are investigated by dynamical mechanical analysis in the vicinity of the incommensurate-commensurate phase transition. We show for the first time, that the anomaly of the elastic compliance coefficient S55, even of purified crystals, is accompanied by typical nonequilibrium phenomena such as isothermal relaxations. The S55(T) anomaly was not significantly enhanced by the purification treatment. We conclude, that extended defects induced during crystal growth have a decisive influence on the elastic properties of [N(CH3)4]2CuCl4.
- ItemFerroelectric domain structures in PZN-8%PT single crystals studied by scanning force microscopy(Technická Univerzita v Liberci, 2001) Abplanalp, M.; Barošová, Dagmar; Bridenbaugh, P.; Erhart, Jiří; Fousek, Jan; Günter, Peter N.; Nosek, Jaroslav; Šulc, MiroslavDomain structures in unpoled PZN-8%PT single-crystal (001) plates have been investigated by scanning force microscopy in the piezoresponse mode, at room temperature. Regular fingerprint structure of nonferroelastic domains with antiparallel polarization (of typical width 1-2 μm) has been observed. Compared to domain patterns usually observed in other materials, domains are rather diffuse, with irregular domain walls. The latter are preferably oriented parallel to {211}- or {231}-type planes. Antiparallel polarization switching induced by local application of electric field was clearly demonstrated. Probable ferroelastic (110) domain walls have been also identified and corresponding domain structures have been analyzed. © 2001 Elsevier Science Ltd.
- ItemModeling of dynamic ferroelectric hysteresis loops in purified Rb2ZnCl4(1996) Hauke, Tilo; Müller, Volkmar; Beige, Horst; Fousek, JanDynamic hysteresis loops were recorded in the ferroelectric lock-in phase of purified Rb2ZnCl4 crystals at a temperature T=188 K which is 5 K below the incommensurate-commensurate phase transition. The hysteresis loops observed in the frequency range 50 Hz<f<5 kHz can quantitatively be described by a model that treats a sideways shift of planar, nearly regular arranged domain walls as the only mechanism of polarization reversal in Rb2ZnCl4. Due to defect interaction, the velocity v of the domain wall depends nonlinearly on the effective force F acting on it and a scaling behavior v∼(F-Fc)θ with θ=1.45 is observed. © 1996 American Institute of Physics.
- ItemPhotorefractive grating fixing in KNbO3 by ferroelectric domains(1997) Cudney, Richard S.; Bernasconi, Pietro N.; Zgonik, Marko; Fousek, Jan; Günter, Peter N.We report observations of photorefractive grating fixing in potassium niobate at room temperature by means of ferroelectric domains. A grating is recorded while the crystal is simultaneously depoled. By repoling the crystal, the presence of a latent grating is revealed. This fixed grating diffracts light with an efficiency which increases when an electric field is subsequently applied and when it is uniformly illuminated. We explain these observations qualitatively using a previously developed model that involves charge compensation by domain walls, and a new aspect that invokes the creation of new trap sites at the ferroelectric domain walls.
- ItemScanning force microscopy of domain structures in Pb(Zn 1/3Nb 2/3)O 3-8% PbTiO 3 and Pb(Mg 1/3Nb 2/3)O 3-29% PbTiO 3(Technická Univerzita v Liberci, 2002) Abplanalp, M.; Barošová, Dagmar; Bridenbaugh, P.; Erhart, Jiří; Fousek, Jan; Günter, Peter N.; Nosek, Jaroslav; Šulc, MiroslavDomain structures of unpoled as well as poled (along [001]- and [110]-direction) Pb(Zn 1/3Nb 2/3)O 3 (PZN)-8% PbTiO 3 (PT) and Pb(Mg 1/3Nb 2/3)O 3 (PMN)-29% PT single crystals have been investigated by scanning force microscopy (SFM) in the piezoresponse mode, at room temperature. Antiparallel domain structures have been detected mostly in unpoled crystals of both materials, with a fingerprint pattern in (001)-oriented PZN-8% PT crystal. The ferroelastic domain wall has been identified in poled (110)-oriented PZN-8% PT crystal. "Writing" of ferroelectric domains has been performed by applying a dc voltage to the SFM tip. Local re-poling has been observed for all unpoled as well as for poled (001)-oriented crystals at the voltage ±60V. Local electrical switching was successful in poled (110)-oriented PMN-29% PT at higher voltage (±120V) but was not successful in poled (110)-oriented PZN-8% PT crystal. Domain-engineered crystals poled in [110]-direction seem to exhibit more stable (in the sense of local re-poling properties) domain arrangement. Hysteretic d(E) dependencies were observed by local application of an ac voltage. © 2002 American Institute of Physics.
- ItemSpontaneous strain in ferroelastic incommensurate [N(CH3)4]2CuCl4 crystals(1997) Müller, Volkmar; Fuith, Armin H.; Fousek, Jan; Warhanek, Hans; Beige, HorstThe temperature dependence of spontaneous strain is investigated in the ferroelastic lock-in phase of [N(CHs),&CuCIi crystals by thermal mechanical analysis. The critical index of the order parameter modulus is found to be j3 =0.33. Considerable wall displacements have been detected for shear stress as small as a, =2.4kPa which indicates that the mechanical pinning energy is extremely small. 0 1997 Published by Elsevier Science Ltd