Mode spectrum of noncollinear electroacoustic boundary-guided waves in a ferroelectric with a moving strip domain

The mode spectrum of electroacoustic boundary waves guided by a strip domain uniformly moving in a 4-mm ferroelectric is considered in the quasi-static approximation. The motion of the strip domain is found to cause the wave vector of the electroacoustic wave to be noncollinear with the guiding boundaries. The frequency dependences of the phase velocity are presented for the symmetric and antisymmetric modes of the electroacoustic wave. These dependences are compared in the reference system fixed to the strip domain and in the laboratory reference system. It is shown that, at low and moderate frequencies, the symmetric mode of the electroacoustic wave is more efficiently localized by a moving strip domain than by a single domain wall.     

Reflection of electroacoustic waves from a system of moving domain walls in a ferroelectric

The interaction of electroacoustic waves with a periodic domain structure formed in a tetragonal ferroelectric by a finite number of uniformly moving 180° domain walls is considered in the quasi-static approximation. It is established that the inclusion of the domain-wall motion leads to a significant modification of the reflectance spectra of electroacoustic waves according to the number, intensity, and location of the Bragg reflectance peaks.     

Electroacoustic waves confined by a moving domain wall superlattice of a ferroelectric crystal

The dispersion properties of electroacoustic wave modes confined by a superlattice of uniformly moving 180° domain walls in a tetragonal ferroelectric crystal are considered. It is shown that the manifold of partial electroacoustic interfacial waves in the lattice is restricted to the first allowed band, the configuration of which in the plane of spectral variables can significantly vary under the action of the moving domain walls.     

A trapped wave in a ferroelectric with a moving strip domain

The existence of a shear homogeneous plane wave trapped by a strip domain moving uniformly in a tetragonal ferroelectric crystal is demonstrated. Using the nonrelativistic quasistatic approximation and a change to the moving frame of reference, the solution is obtained and the dispersion relation is derived for the spatial spectrum of the trapped wave. The uniqueness of the solution is established in the case of the multiple degeneracy of the roots of the characteristic equation when the trapped wave contains an attached wave in the strip domain. The trapped wave is shown to correspond to the antisymmetric mode of the electroacoustic wave of the strip domain at the initial point of the spectrum branch. The specific features of the spatial resonance of the trapped wave with a shear wave obliquely incident on the strip domain are considered.     

Spin waves in a ferromagnet with a moving domain wall

An exact solution of the equation for spin waves propagating along the normal to the domain wall is derived for a ferromagnet with a 180° domain wall moving at constant speed, and the radiation of spin waves in rf fields is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 66–69, April, 1979.     

Laser generation of acoustic waves at a periodic domain structure in lithium niobate

Generation of coherent acoustic oscillations due to the interaction of laser pulses with the periodic domain structure formed in a lithium niobate single crystal is observed. It is found that the excitation of acoustic waves is most efficient when the generated wavelength is equal to the period of the domain structure. The proposed mechanism of the optical generation of acoustic oscillations consists of the photogeneration of free carriers, which compensate the polarization fields within the domains, and the occurrence of alternating elastic stresses caused by the piezoelectric effect.     

Reflection and refraction of surface acoustic waves by a periodic domain structure

Reflection and refraction of surface acoustic waves by a periodic domain structure formed in lithium niobate is studied. A second harmonic generation is observed. A mechanism underlying the linear and nonlinear interactions of acoustic waves with a periodic domain structure is proposed.     

Integrated ferroelectric millimeter-wave phase shifters with a periodic structure

Integrated phase shifters with a periodic structure that includes BaSrTiO₃ ferroelectric varactors parallel-and series-connected to the transmission line are investigated theoretically and experimentally. The phase shifters are designed for the frequency range 26–32 GHz. The dispersion characteristics and insertion losses in the transmission line of the phase shifters are analyzed with regard to the dependence of the capacitance and loss tangent of the varactors on control voltage and temperature. It is shown that parasitic amplitude modulation in the phase shifters can be suppressed if the connection scheme of the varactors takes into account the voltage dependence of the their loss tangent. In the phase shifters with series-connected varactors, the temperature dependence of the phase shift is much weaker than in those with parallel-connected varactors.     

Numerical analysis of the properties of slit electroacoustic waves

The properties of slit electroacoustic waves that propagate in a system of two semi-infinite piezoelectric media separated by a vacuum gap, in a system consisting of a thin piezoelectric plate and a semi-infinite piezoelectric medium separated by a gap, and in a system consisting of two thin piezoelectric plates separated by a vacuum gap are studied. The process of transformation of slit electroacoustic waves to generalized surface acoustic waves or to Lamb waves is considered.     

Spectrum of magnetostatic waves in a ferromagnet with a moving superlattice of domain walls

The spectral properties of magnetostatic waves in a ferromagnet with a moving periodic domain structure are considered within the exchange-free magnetostatic approximation. It is demonstrated that the Doppler frequency shift caused by the domain-wall motion leads to the splitting of the spectrum of each magnetostatic wave mode into two dispersion branches, namely, into high-frequency and low-frequency branches. It is established that the larger the mode number, the larger the separation between these branches with respect to the mode spectrum in the presence of the static domain structure.     

Interaction of a moving domain wall with surface magnetoelastic waves in yttrium orthoferrite

The amplitude-frequency characteristics of magnetoelastic surface waves excited by moving domain walls in a lamellar yttrium orthoferrite samples are discovered and measured. The results of analysis of the effect of magnetoelastic surface waves on the dynamics of domain walls in this orthoferrite are considered. The nonlinear interaction between magnetoelastic surface waves accompanying a moving domain wall is analyzed.     

Diffraction anomalies in moving periodic structure

Special method is presented for treatment of moving periodic structure. The analyzing of the simplest model reveals the speed-dependent diffraction anomalies. This physical effect only occurs under the slow-wave driving and when transverse resonance condition satisfied. The theory and the results may have significance in interdisciplinary fields associated with moving periodic structure.     

Tunneling of electromagnetic waves through a barrier with a periodic structure

The propagation of an electromagnetic wave through a barrier with a periodic structure is considered. An interesting manifestation of electromagnetic wave tunneling through a barrier with a periodic structure is revealed. Specifically, it is theoretically and experimentally shown that, when an electromagnetic wave passes through a medium with a periodic structure in the diffraction mode within a photonic band gap, the field in the medium is localized near its boundaries. Theoretical calculations have been performed for a cholesteric liquid crystal layer of finite thickness and for a 1D photonic crystal. The experiment was carried out with perfect Si single crystals in reflection from the $ (2\bar 20)$ (2\bar 20) and $ (4\bar 40)$ (4\bar 40) planes using MoK _α X rays.     

Dynamics of the domain structure in a ferroelectric triglycinesulfate crystal

The dynamics of the domain structure in ferroelectrics of order-disorder type like triglycinesulfate is studied. The polarization properties of ferroelectrics with relaxation-type absorption are described in terms of the pseudospin formalism. A kinetic equation describing the polarization dynamics of ferroelectrics is derived using the Hamiltonian of the problem. The domain structure dynamics is obtained for different problem parameters and initial conditions. Analytical results are compared with experimental data.     

Resonance attenuation of ultrasonic waves in a superconductor with a moving vortex structure

Equations describing the interaction of ultrasonic waves with a moving vortex structure are derived. The addition to attenuation and the relative change in the velocity of longitudinal ultrasonic waves due to this interaction are calculated. It is found that when a longitudinal ultrasonic wave propagates along the direction of motion of the vortex structure and the velocity V of the structure is equal to half the velocity of the wave, then anomalous acoustic attenuation occurs and the contribution from the ultrasound-vortex interaction to the velocity of the ultrasonic wave vanishes. It is shown that if the vortex structure moves at a sufficiently high velocity, then (in contrast to the case of the structure at rest) a weakly damping collective mode propagating with velocity 2V arises in the structure. It is this mode that is responsible for anomalous attenuation of longitudinal ultrasonic waves.     

Thermophysical properties of PLZT ferroelectric ceramics with a nanopolar structure

The heat capacity, thermal expansion coefficient, and deformation of the PLZT-9/65/35 compound are studied in the temperature range 150–800 K. Diffuse anomalies are detected in the temperature dependences of the heat capacity and thermal expansion coefficient over wide temperature ranges of 250–650 and 330–550 K, respectively. The anomalous behavior of the heat capacity in the temperature range 250–650 K is shown to be caused by the appearance of two-level states (Schottky anomaly). The results obtained are discussed along with the data of structural and dielectric studies.     

Theory of electroacoustic waves in cloudy atmosphere

A general system of equations of motion of a mixture of weakly charged gas and a dropwise liquid is obtained. Vapor condensation on the drops, electrization of the gas, as well as coagulation of drops are taken into account.     

Propagation of surface acoustic waves in a piezoelectric medium with a periodic groove structure

A system of equations is formulated to describe the propagation of surface acoustic waves in a piezoelectric substrate whose surface has a periodic structure formed by transverse grooves. Dependences of the reflection coefficient and the wave velocity on the geometry of the periodic structure (the width and the depth of the grooves) are obtained in a wide range of variation of these parameters for five different orientations in various piezoelectric crystals (quartz, lithium niobate, lithium tantalate, and langasite).     

Bragg interaction of surface magnetostatic waves with a periodic granular HTSC structure

The Bragg interaction of surface magnetostatic waves with periodic granular HTSC structure has been investigated. The dispersion equation for the coupled waves has been obtained. Resonant absorption of waves near the critical temperature involving the granular structure of the superconductor has been found. The possibility of using the observed effect for making frequency-selective structures and high-speed bolometric photodetectors is shown. Tomsk University. Radio Electronic and Control Systems. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 94–98, October, 1997.