Specific features of propagation of electromagnetic waves in layered magnetic photonic crystals

The general regularities of the evolution of the spectrum of magnetostatic waves in a periodic system composed of alternating ferromagnetic and nonmagnetic layers are analyzed. The spectrum of electromagnetic waves in an infinite periodic system and the coefficient of reflection of a plane electromagnetic wave from a half-space periodically filled with ferromagnetic and nonmagnetic layers are calculated. The dispersion relation is derived and analyzed for surface magnetostatic waves at the interface between the periodic system of layers and vacuum.     

Propagation of surface magnetostatic waves in a one-dimensional magnon crystal of a variable thickness

The propagation of surface magnetostatic waves in a ferromagnetic film of variable thickness having a planar periodic structure in the form of a grating of etched parallel strips (one-dimensional magnon crystal) has been investigated. The dispersion characteristics of surface magnetostatic waves have been calculated using the Wentzel-Kramers-Brillouin method. The intrinsic error of the method has been estimated, and the magnon spectrum of the surface magnetostatic wave has been studied. An analysis of the dispersion characteristics and the transmission capacity of these structures has demonstrated that they can be used for designing narrow-band and comb filters.     

Gulyaev–Bleustein Waves in a Layered Structure of Piezoelectric – Periodic Granular High-Temperature Superconductor Structure

Bragg's interactions of Gulyaev–Bleustein surface waves with a periodic granular high-temperature superconducting medium are studied. Dispersion equations describing the characteristics of surface acoustoelectric waves are derived for piezoelectrics of 4 and 6mm symmetry. Resonance absorption of surface acoustoelectric waves is revealed near the critical temperature. The reflection coefficients for surface acoustoelectric waves in Ba₂Si₂TiO₃ from semi-finite and finite periodic high-temperature superconducting structures are calculated. The results obtained for this model problem can be used for solving similar problems for strong piezoelectrics (e.g., lithium niobate) and for designing tunable frequency selectors and transient bolometric photodetectors.     

Interaction of a surface magnetostatic wave with an inhomogeneous granular HTSC medium

In the present paper the dispersion properties of surface magnetostatic waves (SMSWs) propagating in a stratified structure, ferrite film—high-temperature superconducting layer, have been investigated. The problem of SMSW propagation in an inhomogeneous stratified medium has been solved and the dispersion equation has been obtained. In the solution of this problem, the granular nature of the high-temperature superconducting (HTSC) medium and the exposure to a constant magnetization field have been taken into account. Upon exposure to the constant magnetic field the HTSC film becomes an inhomogeneous anisotropic medium with respect to a variable magnetic field. The nonhomogeneous wave equation describing the SMSW field in a granular HTSC medium has been solved by the method of sequential iterations. Corrections for the SMSW velocity and attenuation, calculated with the use of the exact dispersion equation, are significant in comparison with previously obtained approximate values and exceed 20 and 40%, respectively. The method of analyzing electromagnetic fields in inhomogeneous granular high-temperature media can be used to solve some other problems, where spatially inhomogeneous HTSC media are used. Tomsk State University of Control Systems and Radioelectronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 45–48, April, 1999.     

Granular high-temperature superconductor film in a steady magnetic field

An electrodynamic model is constructed for a granular Josephson high-temperature superconductor film in a steady magnetic field. The field induces anisotropy and spatial inhomogeneity for a high-frequency field. The data can be used in boundary-value treatments for layered structures that include high-temperature superconductor films, and also in research on acoustoelectronic and magnetostatic interactions of surface acoustoelectronic and magnetostatic waves with the high-temperature superconductor medium.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 91–94, August, 1995.     

Dispersion of magnetostatic surface waves in ferrite-htsc structures near the phase transition

We present a detailed study of the dispersion properties of surface magnetostatic waves in layered structures of ferrite and high temperature superconductor (HTSC) layers. We solve the propagation problem for the surface magnetostatic waves under a quasistatic approximation, and obtain the dispersion relation. We present an analysis of this dispersion near the phase transition temperature in the HTSC layer. The calculations show that when the HTSC material transforms to the superconducting state the dispersion properties of the magnetostatic waves changes suddenly: the damping decreases by 4–10 dB and the phase velocity increases by a factor of 2–4. These results support experiments which have been performed, in which surface magnetostatic waves have been studied in a YIG film with gallium impurities and a YBaCuO film on a lithium niobate substrate.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 50–55, March, 1995.     

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.     

Propagation of magnetostatic backward surface waves in ferrite-insulator-metal structures magnetized by linearly nonuniform magnetic fields

A theoretical study is made of the trajectories and of the changes in magnitude and direction of the wave vectors of magnetostatic backward surface waves with different frequencies propagating in ferrite-insulator-metal structures with different insulating layer thicknesses and magnetized by a linearly nonuniform static field. It is shown that both forward and backward magnetostatic surface waves (MSSWs) propagate in a waveguide channel, on one side of which MSSWs undergo mirror reflection and on the other side of which their propagation direction is rotated, independently of the thickness of the insulator in the structure. It is shown that when MSSWs propagate in a nonuniform field, the forward wave is converted into a backward wave and, under certain conditions, the backward wave is converted into a forward wave. Some features of the propagation characteristics of magnetostatic backward surface waves are determined. Zh. Tekh. Fiz. 69, 70–77 (February 1999)     

Wideband chaotic oscillation in a self-oscillatory system with a nonlinear transmission line on magnetostatic waves

Wideband chaotic microwave oscillation in a ring self-oscillatory system is studied. The system includes a solid-state power amplifier and a wideband nonlinear transmission line with a ferromagnetic film in which magnetostatic waves of different types are excited. It is found that the eigenmodes of the self-oscillatory system excited in the passband of the transmission line on magnetostatic waves become noisy because of spin wave parametric excitation due to the magnetostatic wave and nonlinearity of the power amplifier. A continuous spectrum of modes observed in the wideband chaotic signal is associated with the presence of a descending portion in the dynamic characteristic of the nonlinear transmission line, which arises when a magnetostatic surface wave is excited.     

The propagation of magnetostatic surface waves in ferrite/superconductor structures

An electrodynamic model that describes the dispersion of magnetostatic surface waves in ferrite/superconductor structures is suggested. On its basis, a new approach to determining the microwave sheet resistance R _S of superconducting films in a magnetic field is elaborated. The values calculated (R _S =0.20–0.96 mΩ) agree with results obtained by the Tauber method. For YIG/YBCO structures, the controllable phase shift is about 1.5π when the depth of magnetostatic wave penetration into the YBCO film varies from 2.0 to 0.8 μm.     

Emission of noise-like spin wave packets in the presence of three-magnon decay processes and the kinetic instability of waves in a ferromagnetic film

The features of spin wave emission from a ferromagnetic film in the direction of the propagation of a surface magnetostatic wave have been experimentally investigated at various input signal powers. Radiation in the form of two noise-like spin wave packets has been detected near the frequency corresponding to half the pump frequency. This radiation is caused by three-magnon processes of the decay of a surface magnetostatic wave and by the kinetic instability of spin waves.     

The effect of parametrically excited spin waves on the dispersion and damping of magnetostatic surface waves in ferrite films

This paper describes an experimental study of variations of the dispersion and damping of magnetostatic surface waves in ferrite films, caused by three-and four-magnon interactions with parametric spin waves excited by an auxiliary surface magnetostatic pump wave with frequency f _p. The variations in the dispersion and damping were identified, respectively, with variations Δk″ in the real part and Δk′ in the imaginary part of the wave number of the surface magnetostatic wave. The Δk″ and Δk′ values were determined from the ratio of the changes of the phase increment Δφ and the amplitude increment ΔA of the surface magnetostatic wave to the length L of the nonequilibrium section of the film, where the parametric spin waves exist. It is found that, when three-magnon decay processes are allowed for the pump wave and the surface magnetostatic probe wave, the probe wave can substantially alter the distribution of the parametric spin waves in the film. Zh. éksp. Teor. Fiz. 115, 318–332 (January 1999)     

Influence of a constant magnetic field on the dispersion of surface magnetostatic waves in a structure consisting of ferrite and granular high-temperature superconductor

The dispersional properties of a surface magnetostatic wave (MSW) in a laminar structure consisting of ferrite film and a high-temperature superconducting (HTSC) layer are studied in detail. The propagation of surface MSW in this structure is investigated, and the dispersional equation is obtained; the granular character of the HTSC films and the influence of constant magnetic field are taken into account here. The magnetic field is responsible for breakdown of the Josephson layer of granular HTSC films and the appearance of nonsuperconducting layers close to the film surface. It follows from the calculation results that, when the HTSC film passes to the superconducting state, the dispersional characteristics of the MSW undergo a discontinuity. The magnitude of the discontinuity depends on the film thickness, the critical current, and the granule size. The results obtained may be used in designing various microelectronic devices based on granular HTSC films. Tomsk State Academy of Control Systems and Radioelectronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 72–77, June, 1996.     

Parametric interaction of volume magnetostatic waves in a ferrite film with spatiotemporal modulation of the magnetic field

Effects of the resonant Bragg scattering of magnetostatic backward volume waves on the periodic structure of a conductive meander pattern with an alternating current are analyzed theoretically and compared with experiment. It is shown that unlike a static grating, a dynamic grating causes a frequency shift of the scattered wave. It is proposed that this phenomenon be utilized for effective control of the intermodal conversion of magnetostatic waves. Zh. Tekh. Fiz. 68, 105–112 (May 1998)     

Magnetostatic spin waves in (111)-oriented thin garnet films with combined cubic and uniaxial anisotropies

The magnetostatic spin wave theory in (111)-oriented ferromagnetic films characterized by cubic and uniaxial anisotropies (CUA) is developed. The theory is discussed for two cases when the magnetization vector is perpendicular or parallel to the sample plane. In CUA films, instead of the usually discussed magnetostatic surface waves known for the isotropic case, a new type of surface waves was found with the complex wavevector component normal to the surface.It is shown that for the pure yttrium-iron-garnet film the influence of the CUA effects on the dispersion characteristics of the surface waves is not very substantial.     

Sagnac effect in ring interferometers on “slow” waves

We consider the Sagnac effect in ring interferometers on magnetostatic and surface acoustic waves. It is shown that the Sagnac effect for waves of arbitrary type (including both magnetostatic and surface acoustic waves) propagating in an arbitrary medium cannot be calculated using Galilean transformations but is explained within the framework of the special relativity and is related to the difference between the phase velocities rather than group velocities of counter-propagating waves in the rotating reference frame. We also show that the phase difference of counterpropagating waves due to the Sagnac effect depends on neither the phase velocity of the wave in a medium at rest nor the dispersion of the medium; it depends only on the wave frequency and the angular velocity of interferometer rotation. The minimum angular velocity that can be measured in the ring interferometers using magnetostatic and surface acoustic waves is estimated. N. I. Labachevsky State University, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 4, pp. 373–382, April 1999.     

Surface Acoustoelectric Waves in a Piezoelectric–High-Temperature Granular Superconductor Layered Structure

Interactions of surface acoustoelectric waves with a granular high-temperature superconducting medium are studied. Dispersion equations describing the characteristics of surface acoustoelectric waves are derived for piezoelectrics of 4 and 6mm and 3m symmetry. It is shown that at a temperature above the critical point an attenuation jump and a sudden change in the phase velocity of surface acoustoelectric waves are observed. This effect increases with increase in the electromechanical coupling coefficient and decrease in the thickness of the high-temperature superconducting film. The results obtained can be used in designing frequency selectors and transient photodetectors.     

Spectrum and losses of surface magnetostatic waves in a 1D magnon crystal

The spectrum and propagation losses of a surface magnetostatic wave in a 1D ferrite magnon crystal are experimentally studied as a function of angle φ between the wavevectors of the surface magnetostatic wave and periodic crystal lattice. Variation in the positions of Bragg forbidden bands with angle φ is described. A wide transmission band is discovered near long-wave frequency boundary f ₀ of the surface magnetostatic wave in a narrow interval of angles around φ ≈ 57°. In the interval 70° < φ < 90° and at frequencies below f ₀, there exists a magnetostatic wave with a wavevector that is normal to the bias field.     

Features of surface and volume magnetostatic waves in a tangentially magnetized slab

A special direction of the wave vector was found for volume magnetostatic waves (MSWs) that coincides with the cutoff angle for surface MSWs; when crossing this direction, the field configuration for MSWs with small wavenumbers changes sharply. It is shown that this direction corresponds to the maximum asymmetry of magnetostatic potential distribution over the film depth and the largest wave penetration depth into the film bulk from the surface. This effect occurs also for volume MSWs propagating in a wave channel.     

Interaction of magnetostatic waves with current carriers in stratified structures

The interaction of magnetostatic waves with charge carriers in ferrite-semiconductor and ferrite-electron flux structures is reviewed. The basic equations needed to calculate the interaction effects in these structures are provided. Attention is turned to the possibility of amplifying fast magnetostatic waves in bodies of revolution by means of circular electron drift over the body surface. The possibility is discussed of amplifying magnetostatic waves in a ferrite film by an electron flux band. The interaction of magnetoelastic waves with electrons in ferrite-semiconductor structures is considered. A method of calculating the static EMF (electromotive force), induced by traveling MSW (magnetostatic waves) in a ferrite-semiconductor structure, is discussed. Attention is turned to circular currents, flowing in the semiconductor, which can vary substantially the longitudinal EMF and lead to generation of a transverse EMF in the structure. We discuss experimental studies on detection of interaction of magnetostatic waves with charge carriers, suggesting the possibility of wave amplification in ferrite-semiconductor and ferrite-electron flux structures, and exploring EMF induction mechanisms in the regime of traveling waves and ferromagnetic resonance.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 5–29, January, 1989.