Search results for "waves"
showing 10 items of 1766 documents
Nonlocal model for a magneto-electro-elastic nanoplate
2013
A mathematical model based on nonlocal third-order shear deformation plate theory has been developed to evaluate the mechanical and electromagnetic behavior of magneto-electro-elastic nanoplates. Two types of magneto-electro-elastic composites have been considered, all of them combination of Barium Titanate sheets, that represents the piezoelectric phase, and Cobalt Ferrite, that is the piezomagnetic component. Setting magneto-electric boundary conditions on each laminate, it has been possible to extrapolate and to analyze free vibrations frequencies for all considered plates, allowing to do objective assessments on what factors influence laminate modes and, especially, how these vary in th…
Piezoelectric coefficients by molecular dynamics simulations in the constant stress ensemble: A case study of quartz
2006
Piezoelectric (strain) coefficients dij of quartz are calculated in terms of molecular dynamics as a function of pressure and temperature. We review the necessary formulas for the computation of electromechanical materials coefficients obtained at constant stress and temperature, and discuss how to overcome complications of the definition of polarization variations due to fluctuating box geometries. A method is employed suppressing significantly stochastic fluctuations of the estimators for piezoelectric coefficients. A recently suggested force field for the simulation of SiO2 reproduces available experimental data quite accurately. Predictions are made for the pressure dependence of dij of…
Atomistic simulation of the [001]surface structure in BaTiO3
1997
Abstract We simulate the effect of the surface relaxation on the polarization of the layers of paraelectric phase in the vicinity of the [001] surface in BaTiO 3 in the framework of the shell-model potentials. We observe large polarization of ions in the first two layers of the surface. Our simulations confirm the possibility of existence of Ti- and Ba-containing top layers in [001] BaTiO 3 surfaces.
Diffraction-efficiency oscillations in amorphous As_2S_3 films
1999
An experimental study of the holographic gratings recorded in nonannealed, thermally with time relaxed amorphous As2S3 films by 514.5-nm light in the presence of 632.8-nm readout light is carried out. The dependences of the maximal first-order diffraction efficiency on the holographic grating period was studied in a wide range of periods, from 0.40 to 70.0 µm. A peculiar oscillatory diffraction-efficiency temporal behavior occurring under certain conditions is reported. The obtained results are discussed in terms of photoinduced structural changes, relaxational structural changes, photoinduced anisotropy, and photoinduced recharging of the localized states in the bandgap. The diffraction-ef…
Spin resolved photoemission study of Co(0001) films
1996
Abstract Thin ferromagnetic films are of great practical interest as they can exhibit a different magnetic behaviour compared to the bulk crystals due to, e.g., the surface anisotropy. The electronic and magnetic properties of thin cobalt films evaporated on W(110) have been investigated by means of angle and spin resolving photoelectron spectroscopy. The study was focused on electron spin polarization, spin resolved intensities and band structure behaviour in dependence of film thickness, excitation energy, and photoelectron detection angle. In order to interpret the experimental results, we have performed relativistic band structure calculations for the Co(0001) surface. The observed agre…
Electric-Field Control of Spin-Orbit Torques in Perpendicularly Magnetized W/CoFeB/MgO Films
2020
Controlling magnetism by electric fields offers a highly attractive perspective for designing future generations of energy-efficient information technologies. Here, we demonstrate that the magnitude of current-induced spin-orbit torques in thin perpendicularly magnetized CoFeB films can be tuned and even increased by electric-field generated piezoelectric strain. Using theoretical calculations, we uncover that the subtle interplay of spin-orbit coupling, crystal symmetry, and orbital polarization is at the core of the observed strain dependence of spin-orbit torques. Our results open a path to integrating two energy efficient spin manipulation approaches, the electric-field-induced strain a…
Bulk spin polarization of magnetite from spin-resolved hard x-ray photoelectron spectroscopy
2021
Physical review / B 104(4), 045129 (1-10) (2021). doi:10.1103/PhysRevB.104.045129
Interface-induced enhancement of piezoelectricity in the (SrTiO 3 ) m /(BaTiO 3 ) M−m superlattice for energy harvesting applications
2019
This research is funded by the Latvian Council of Science, project No. lzp-2018/1-0147. The computer resources were provided by Stuttgart Supercomputing Center (project DEFTD 12939) and Latvian Super Cluster (LASC). Many thanks to R. Dovesi, A. Erba, and M. Rérat for numerous stimulating discussions.
Direct observation of polar nanostructures in PLZT ceramics for electrooptic applications
2004
ABSTRACTTransparent Pb1-yLay(Zr1-xTix)1-y/4O3(PLZT, y=0.0975, x=0.35) ceramics prepared via hot pressing techniques were studied via piezoelectric force microscopy (PFM). Clear piezoelectric contrast is observed in a cubic relaxor phase indicating spatial distribution of polarization with an average cluster size of about 50 nm. The irregular polarization pattern is associated with the formation of a glassy state, where random electric and stress fields are responsible for the disruption of the long-range ferroelectric order. Local poling of the ceramics resulted in the formation of a stable micron-size domain that could be continuously switched under varying dc bias (local hysteresis loop).…
Field Induced Evolution of Nanoscale Structures in Relaxor PLZT Ceramics
2005
Abstract The kinetics of the nanoscale structures under application of bipolar and unipolar ac field was investigated by recording of the switching charge in wide temperature and field range in hot-pressed relaxor PLZT ceramics. Original analysis of the switching charge data was based on the consideration of the field induced transformation as an evolution of the nanoscale domain structure with nanoscale nonpolar inclusions. We have shown that the inhomogeneous depolarization field produced by the bound charges existing at the interphase boundaries play the key role in spontaneous backswitching effects.