Search results for "Polarization"
showing 10 items of 1884 documents
Domain-Enhanced Interlayer Coupling in Ferroelectric/Paraelectric Superlattices
2004
We investigate the ferroelectric phase transition and domain formation in a periodic superlattice consisting of alternate ferroelectric (FE) and paraelectric (PE) layers of nanometric thickness. We find that the polarization domains formed in the different FE layers can interact with each other via the PE layers. By coupling the electrostatic equations with those obtained by minimizing the Ginzburg-Landau functional we calculate the critical temperature of transition Tc as a function of the FE/PE superlattice wavelength and quantitatively explain the recent experimental observation of a thickness dependence of the ferroelectric transition temperature in KTaO3/KNbO3 strained-layer superlatti…
AC Switching of Relaxor PLZT Ceramics
2005
The switching under application of bipolar ac field is studied by recording of the hysteresis loops in wide temperature and field range in PLZT x/65/35 ceramics. The qualitative difference of the shape of hysteresis loops above and below the freezing temperature is attributed to backswitching in relaxor phase due to the depolarization field produced by the bound charges located at the interphase boundaries. The application of the quasistatic approach to analysis of the experimental data allows us to obtain parameters of the distribution function of local coercive fields from the field dependence of the switching charge derivative on field.
Multiferroic BiFeO<inf>3</inf> for conductance control at the LaAlO<inf>3</inf>/SrTiO<inf>3</inf>-interface
2015
Multiferroic materials possessing both magnetic and ferroelectric order enable in principle to switch order parameters using not the direct reciprocal field, e.g. to switch the magnetization by an electric field or the electric polarization by a magnetic field. A recent breakthrough was achieved by the demonstration of the ferromagnetic switching of a Co layer with an electric field employing the multiferroic BiFeO 3 [1]. The latter material is a perovskite based oxide that shows stable ferro-electricity as well as an antiferromagnetic order at room temperature [2,3]. Due to a Dzyaloshinskii-Moriya interaction induced by rotation of oxygen octahedra leading to noncollinear Fe-O-Fe bonds a s…
Continuous theory of switching in geometrically confined ferroelectrics
2014
A theory of ferroelectric switching in geometrically confined samples like thin films and multilayers with domain structure has been proposed. For that we use Landau–Khalatnikov (LK) equations with free energy functional being dependent on polarization gradients. In this case, the consistent theory can be developed as for thin ferroelectric films and multilayers the domain structure reduces to Fourier series in ferroelectric polarization. The specific calculations are presented for thin film ferroelectric with dead layers and ferro-/paraelectric multilayer. Our theory is generalizable to ferroelectrics and multiferroics with other geometries.
Depolarization Field and Properties of Thin Ferroelectric Films with Inclusion of the Electrode Effect
2005
The influence of metallic electrodes on the properties of thin ferroelectric films is considered in the framework of the Ginzburg-Landau phenomenological theory. The contribution of the electrodes with different screening lengths l s of carriers in the electrode material is included in the free-energy functional. The critical temperature T cl , the critical thickness of the film, and the critical screening length of the electrode at which the ferroelectric phase transforms into the paraelectric phase are calculated. The Euler-Lagrange equation for the polarization P is solved by the direct variational method. The results demonstrate that the film properties can be calculated by minimizing t…
Spin-polarized Low Energy Electron Diffraction
2007
We review recent progress in the understanding of the physics of ultrathin ferromagnetic films and surfaces that has been made using elastic spin-polarized low-energy electron diffraction (SPLEED). Further development of the experimental technique including high efficient electron sources, spin manipulation and imaging allows a wide range of applications. We report on a quantitative comparison of relativistic dynamical scattering calculations with SPLEED experiments on Fe(110) surfaces and Fe(100)/W(100) thin films leading to an understanding of the spatial distribution of spin densities. Exploiting the surface sensitivity in combination with the large asymmetry of SPLEED, it becomes feasib…
Electrical transport with temperature-induced spin disorder in NiMnSb
2019
Abstract We investigate theoretically the combined effect of phonons and magnons caused by finite temperatures on the electrical resistivity of nonstoichiometric half-Heusler NiMnSb alloy. The coherent potential approximation within the alloy analogy model is employed for an efficient treatment of chemical impurities, atomic displacements, and magnetic disorder. Spin fluctuations of local Mn moments are described by two models: (i) uncompensated disordered local moment approach and (ii) tilting of the moments. The calculated resistivity agrees with experimental data, the agreement is good up to 600 K. We show that a strong magnetic disorder leads to a violation of the Matthiessen’s rule for…
New Heusler Compounds and Their Properties
2013
Spintronics is a multidisciplinary field and a new research area. New materials must be found for satisfying the different types of requirement. The search for stable half-metallic ferromagnets and ferromagnetic semiconductors with Curie temperatures higher than room temperature is still a challenge for solid state scientists. A general understanding of how structures are related to properties is a necessary prerequisite for material design. Computational simulations are an important tool for a rational design of new materials. The new developments in this new field are reported from the point of view of material scientists.
Relation between deformation and polarization in the region of diffused phase transition of plzt 8/65/35
1995
Abstract The deformation as a function of polarization was measured in PLZT 8-10/65/35 in the region of diffused phase transition. A different behaviour of deformation in the region of double hysteresis loops was observed corresponding to ferroelectric and nonpolar phases as well as to the field induced phase transition region. In the ferroelectric phase the results are described by electrostriction. The decrease of volume as well as small longitudinal deformations at the field induced transition to ferroelectric state are explained by large remanent deformations, existing in the nonpolar phase. Since description of deformation in the framework of electrostriction cannot be motivated in the…
Magnetic field tuning of the smart materials domain structure
1998
The investigation of the behavior of the ferroelectric phase transition with magnetic filed tuning and concentration change is highly attractive owing to the possibility to prepare alloying samples and to predict theoretically the parameters of the magnetic field and concentration response at relatively small concentrations. These parameters may be extracted from the equation of states of the perovskite under investigation in the assumption of the linear response. The study of the movement of the paraelectric - ferroelectric interphase boundary in (Ba,Sr)TiO 3 with concentration change and in constant magnetic fields is provided in the framework of the mean-field theory. The analytical solu…