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)     

Soliton regimes of surface magnetostatic wave propagation in a magnet-semiconductor structure

The nonlinear properties of exchange-free surface magnetostatic spin waves in a layered structure containing films of a ferromagnet and a semiconductor are investigated theoretically. The stability of nonlinear surface magnetostatic waves relative to longitudinal disturbances is investigated using the envelope evolution equation in the weak-nonlinearity approximation. It is shown that, under certain conditions, a surface spin-wave pulse propagates in the form of an envelope soliton. Calculations are performed for the case of an yttrium iron-garnet-indium antimonide structure. Fiz. Tverd. Tela (St. Petersburg) 41, 1272–1275 (July 1999)     

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)     

Magnetostatic surface waves produced by an inhomogeneity of the anisotropy with a turning point of the spectral function on a ferromagnet surface

Magnetostatic surface waves with fixed frequency and wave vector are predicted to exist in a ferromagnet with an inhomogeneity of the magnetic anisotropy such that the spectral function has a turning point on the surface. This result is most important for the case when an external magnetic field magnetizes the ferromagnet perpendicular to its surface. The frequency of the surface wave is determined by the frequency of the magnetostatic volume wave at the surface of the ferromagnet, and the wave vector is determined by the surface values of the local magnetic anisotropy field and its derivative. Zh. Tekh. Fiz. 68, 118–123 (June 1998)     

载流子影响下铁磁膜中静磁孤子的存在性分析

铁磁膜近邻存在半导体载流子的影响下,静磁表面波在一定频率范围内与外加恒磁场相垂直的传播方向上能演化成静磁孤子,而且静磁表面波群速在一定频率范围会改变运动方向成为反向波,其大小受载流子浓度的影响 关键词： 静磁孤子 载流子 铁磁膜 静磁表面波     

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.     

Field distribution of magnetostatic waves in a tangentially magnetized ferromagnetic slab

The field distribution of magnetostatic surface and volume waves as they propagate at an arbitrary angle to a constant field in a tangentially magnetized ferromagnetic slab (Damon-Eschbach waves) is investigated. Snapshots of the magnetic field lines of the wave are constructed. The variation of the magnetic field distribution with thickness is qualitatively identified for a volume wave as it propagates at an angle equal to the cutoff angle of the surface wave, as a result of which the sinusoidal profile of the wave over thickness almost discontinuously acquires an additional phase difference. Zh. Tekh. Fiz. 69, 82–86 (January 1999)     

Influence of the pinning of Abrikosov vortices on the propagation of surface magnetostatic waves in a ferromagnet-superconductor structure

The influence of surface-layer vortex pinning in a type-II superconductor on the propagation of surface magnetostatic waves in a ferromagnet-superconductor structure is analyzed. The pinning is assumed to be strong enough to prevent vortex displacement under the influence of the Lorentz force generated by the surface magnetostatic waves, so that the ground state of the superconductor is determined by the elastic properties of the vortex lattice and by pinning. In the given model the problem reduces to the analysis of the wave spectrum in the scattered field created by the disordered vortex surface layer. A calculation shows that the influence of this field on the surface magnetostatic-wave spectrum is slight and, hence, degradation of the shielding properties of the superconductor does not take place in the presence of strong vortex pinning (as opposed to the ferromagnet-ideal superconductor structure). Fiz. Tverd. Tela (St. Petersburg) 40, 32–35 (January 1998)     

Magnetostatic volume waves in exchange-coupled ferrite films

The influence of exchange coupling of layers on the propagation of magnetostatic dipole volume waves in normally and tangentially magnetized two-layer epitaxial ferrite structures is investigated. It is shown that the indicated influence is manifested in the form of dynamic spin pinning effects on the interlayer boundary and formation of a common dipole-exchange wave spectrum for the entire structure. In this case, at the synchronism frequencies of the dipole and exchange waves the losses of the dipole waves grow and anomalous segments appear in the dispersion. In films magnetized in the “hard” direction relative to the axis of normal uniaxial surface anisotropy the magnetostatic dipole volume waves can interact resonantly with the surface spin waves supported by the boundaries with pinned spins. Zh. Tekh. Fiz. 68, 97–110 (July 1998)     

Parametric interaction of magnetostatic waves with a nonstationary local pump

A solution is obtained for the general problem of the nonstationary interaction of backward volume magnetostatic waves in films of yttrium-iron garnet with local parametric pumping. In the case of a large pump region, l≫λ, where λ is the wavelength of the backward volume magnetostatic waves, the problem reduces to a system of truncated equations for two packets of counter propagating waves. In the opposite case, l<λ, the exact problem of parametric interactions of the eigenmodes of a ferrite film (both counterpropagating and in the same direction) is solved numerically. Both cases are studied experimentally and good qualitative and quantitative agreement is obtained with the theory. For the first time, the reversal of a wave front and the time reversal of the shape of backward volume magnetostatic wave pulses are observed and a change in the propagation time for the peak of the signal pulse and a reduction in its width owing to pumping are recorded. Two operating regimes are identified for a nonstationary parametric backward volume magnetostatic wave amplifier with local pumping, which differ in the ratio of the duration of the pump pulse to the transit time for the wave through the local pump region, and the effect of the parametric excitation of two-dimensional spin waves on the interaction of backward volume magnetostatic waves with a local nonstationary parametric pump is determined. Zh. éksp. Teor. Fiz. 116, 2192–2211 (December 1999)     

Bulk and surface excitations in magnetoactive periodic semiconductor heterostructures

We have theoretically investigated the dispersion characteristics of bulk and surface excitations in a magnetoactive periodic semiconductor heterostructure (PSH) using a local theory in the nonretardation limit (c → ∞). The computation has been performed treating the unit cell of the heterostructure as made up of an array of alternate n-type GaAs (in A-type region) and n-type InSb (in B-type region) slabs of equal widths. The presence of the high magnetostatic field (B₀) gives a rich spectrum of the bulk excitations. A new type of surface polariton mode is found in a complete analogy with the one occurring at the surface of a semiconductor superlattice as predicted by Giuliani and Quinn. The frequency-dependent inverse penetration depth for this new magnetoplasma surface polariton has also been computed as a function of wave vector component parallel to the layers. We discuss our analytical and numerical results in the light of the recent work on heterostructures/superlattices.     

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.     

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)     

Self-consistent problem of the excitation of beams of magnetostatic waves

An analytical solution is obtained for the self-consistent problem of the excitation of beams of magnetostatic waves by a converter of arbitrary type. Radiation patterns are calculated numerically for stripline converters at the frequencies where magnetostatic surface waves exist. Zh. Tekh. Fiz. 68, 95–101 (August 1998)     

Magnetostatic analog of Love surface elastic waves

The possibility of the existence of a magnetostatic analog of Love surface elastic waves is predicted. They appear in situations where the conditions for the existence of magnetostatic volume waves hold in the upper layer of a ferromagnetic bilayer, but not in the lower layer. Zh. Tekh. Fiz. 68, 85–90 (October 1998)     

Bragg Interaction of Surface Magnetostatic Waves with a Periodic Granular High-Temperature Superconducting Structure

Bragg interaction of surface magnetostatic waves with a periodic granular high-temperature superconducting structure is studied. A dispersion equation for coupled waves describing the characteristics of surface magnetostatic waves is derived. Resonance wave absorption near the critical temperature is revealed. The magnetostatic wave reflection coefficients of semi-infinite and finite periodic high-temperature superconducting structures are calculated. The results obtained can be used in designing tunable frequency selectors and transient bolometric photodetectors.     

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.     

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.     

Four-magnon decay of magnetostatic surface waves in yttrium iron garnet films

The four-magnon instability of magnetostatic surface waves (MSSWs) in yttrium iron garnet epitaxial films is investigated experimentally. It is shown that four-magnon instability for MSSWs with wave numbers 30–600 cm⁻¹ is a decay instability and develops for values of the wave magnetization close to the threshold level for second-order parametric instability of a homogeneous transverse pump wave. When the supercriticality of the MSSW power is 15–20 dB, the generated parametric spin waves themselves become unstable with respect to the four-magnon interaction, so that kinetic instability develops in the film. It is shown that the pump signal transmitted through the signal and the length of the “nonlinear” part of the film, where a MSSW is capable of exciting parametric spin waves, increase as the pump power is increased. Fiz. Tverd. Tela (St. Petersburg) 38, 330–338 (February 1997)     

Amplification of an acoustic wave in inhomogeneous Piezoelectric semiconductors

The theory of the amplification of an acoustic wave in an inhomogeneous piezoelectric semiconductor in the presence of a transverse magnetostatic field is developed assuming the explicit dependence of the relaxation time (τ) on the position coordinate. It is found that the implication of the sound wave is possible even if the drift velocity of the electron is smaller than the velocity of sound in the medium.