Properties of noncollinear magnetostatic waves in magnetic films

Some effects and phenomena that can be implemented in ferrite films using dipole spin or magnetostatic waves are described.     

Parametric excitation of magnetostatic fluctuations by ion-cyclotron waves

It is shown that in an inhomogeneous plasma the magnetostatic fluctuations can be excited to superthermal level by ion-cyclotron waves. The growth rate of the ensuing parametric instability is calculated using some typical tokamak parameters.     

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)     

Parametric excitation of spin waves in a nonlinear magnetostatic resonator

A theory of spin wave parametric instability is developed that simultaneously allows for cubic anisotropy and first- and second-order uniaxial anisotropies. The contributions of various anisotropies to a dispersion relation and first-and second-order nonlinearity coefficients are considered. A technique for studying the parametric instability of oscillations in magnetostatic resonators that relies on measuring their Q factors is proposed. Measuring data are used to determine the relaxation frequencies of parametrically excited spin waves in yttrium iron garnet films at frequencies close to 1 GHz. It is shown that a nonlinearity in the bias dependence of the spin wave frequencies should be allowed for in studying the relaxation parameters of ferrites.     

Self-focusing magnetostatic beams in thin magnetic films

The possibility of generation of stable self-focusing beams in in-plane magnetized thin magnetic films is considered, and theoretical conditions for the existence of such localized solutions are discussed. It is shown that for the definite direction between static magnetizing field and preferential direction of radiation from a microwave antenna, the problem reduces to the one-dimensional nonlinear Schrödinger equation. For such angles it is possible to generate stable self-focusing beams. Particular values of beam width and propagation angles versus magnitude of magnetizing field are calculated in order to suggest a realistic experimental setup for the observing the discovered effect.Received: 3 July 2004, Published online: 12 October 2004PACS: 85.70.Ge Ferrite and garnet devices - 75.30.Ds Spin waves - 76.50. + g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance     

Quasi-solitons of magnetostatic waves in a two-layer structure under single-mode excitation

We investigate the quasi-solitons of the envelope of forward body magnetostatic waves in a structure that consists of two magnetically coupled films separated by a nonmagnetic interlayer under the initial excitation of a pulse in one of them. We have found that as the pulse propagates, its energy is transferred from one film to the other through intermode coupling; as a result, “pulsating” quasi-solitons of the coupled modes of the two films emerge. We show that the amplitude of each of the mode pulses at the exit from the waveguide can be regulated over a wide range by varying the magnetizing field.     

Bragg diffraction of surface magnetostatic waves from magnetic lattices

We present a theoretical and experimental investigation of Bragg scattering of surface magnetostatic waves (SMSW) by a time-independent, spatially periodic magnetic field when the wave orientation is arbitrary with respect to the magnetization field. In the theoretical section the theory of single-mode Bragg diffraction is generalized to the case of waves with arbitrary dispersion propagating through an anisotropic medium. The calculated results are, on the whole, supported by experimental measurements on SMSW. We demonstrate that a geometry which in isotropic media leads to a sinusoidal distribution of diffraction order amplitudes as a function of penetration into the differing lattice, can lead to a nearly exponential distribution of such amplitudes in anisotropic media. The anisotropy of the interaction between SMSW and the magnetic diffracting lattice is manifested by anomalously high scattering efficiencies for certain cases of relative orientation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 76–85, November, 1988.     

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)     

Positive and negative magnetostatic coupling in two-layer magnetic films

The energy of positive and negative magnetostatic coupling has been measured in two-layer Fe-Ni-Co ¦SiO¦ Fe-Ni-Mo films for intermediate SiO layers having thicknesses of from 100 to 1500 Å. The intermediate-layer thickness corresponding to a transition from positive to negative coupling was determined for a series of films having a constant magneticlayer thickness.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 11–16, November, 1969.     

On the excitation and propagation of magnetoelastic and magnetostatic waves in inhomogeneously magnetized monocrystals

Results are presented of the experimental study of the excitation of magnetoelastic and magnetostatic waves in monocrystalline prisms of iron garnets magnetized by an inhomogeneous external field with a longitudinal component decaying in the axial direction. Application of such excitation conditions to the reduction of the working frequencies of controllable microwave delay lines is considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 53–56, September, 1981.     

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)     

Indicatrices of magnetostatic surface waves

Indicatrices (isofrequency curves) of magnetostatic surface waves are studied with allowance for wave attenuation. A bias magnetic field is applied tangentially to a ferrite film. Arbitrary angles between the bias magnetic field and the wave vector are examined.     

Propagation of magnetostatic waves in the form of rectangular pulses in YIG films

The effect of dispersion on the propagation of linear rectangular pulses of magnetostatic waves in YIG films is studied. With surface magnetostatic waves propagating in YIG films and composite ferrite-insulator-metal structures, it is demonstrated that, for the near-rectangular phase-unmodulated input pulse and the distance between input and output transducers equal roughly to half the dispersion length of the pulse, the FWHM of the output pulses is 50–60% of the initial value. This fact can be used for estimating the dispersion coefficient of magnetostatic waves.     

Parametric excitation of magnetic electron drift vortex modes by Langmuir waves

A new multi-dimensional parametric interaction coupling Langmuir waves with magnetic electron drift vortex modes is presented. A general dispersion relation for the parametric instabilities is derived, and the growth rates of the decay and modulational instabilities are obtained. The present instabilities can be the source of large-scale magnetic fields near the critical surface of a laser-produced plasma.     

Dispersion relation for surface-localized magnetic polaritons and magnetostatic waves in antiferromagnetic superlattice

In addition to the general dispersion equation for surface-localized magnetic polaritons and magnetostatic waves, which propagate in the system antiferromagnetic superlattice-antiferromagnet, we derive a simplified result for the long-wavelength limit λ?L (L is the period of superlattice) when the superlattice is found to behave like an anisotropic bulk medium (effective-medium approach). The dispersion curves and frequency region of the existence of the surface magnetic polaritons and magnetostatic waves are presented numerically for several values of the external magnetic field and for different antiferromagnetic materials.     

Propagation of magnetostatic waves in unsaturated ferrite films with a strip domain structure

The propagation of surface and volume magnetostatic waves in unsaturated films of yttrium iron garnet is studied experimentally for the case when the wavelength greatly exceeds the domain width, while the domain width is comparable to the film thickness. The characteristics of these waves are examined for symmetric linear, asymmetric linear, and symmetric zigzag strip domain structures in the films. These characteristics cannot be explained by a theory based on averaging the magnetization over all the domains. Zh. éksp. Teor. Fiz. 111, 1016–1031 (March 1997)     

Focussed surface acoustic waves on an anisotropic crystal, studied by optical probing

Efficient focussing of surface acoustic waves has been achieved using a properly shaped gold film deposit on the −22.3° rotated Y-cut surface of quartz. The acoustic wave field was studied with laser probing techniques. A more than threefold increase in intensity and a tenfold decrease in beam width was observed at the focal point. The focussing action was obtained with the elastic wave equivalent of the Fresnel phase-reversal zone plate of optics. The multiple foci of this device allowed a simultaneous generation of acoustic waves in nearly all directions on the surface. Consequently, the surface wave velocity anisotropy could be determined completely. The experimental results are in very good agreement with the calculated velocity anisotropy. Electromagnetic diffraction theory is adopted to the two dimensional anisotropic system to analyse the performance of the focussing device.     

Dependence of the frequencies of magnetostatic waves on the magnetizing field in ferrite films

Analytical expressions are derived for the derivatives of the frequencies of magnetostatic waves with respect to the external magnetic field in anisotropic ferromagnetic films. Films having cubic anisotropy and 〈100〉, 〈110〉, and 〈111〉 surfaces are analyzed in detail. The frequency-field relations are used in an experimental determination of the temperature coefficients of the cubic anisotropy field and the saturation magnetization in an yttrium iron garnet film. Fiz. Tverd. Tela (St. Petersburg) 40, 2089–2092 (November 1998)     

Rectification of space-charge waves upon optical and electrical excitation

A comparative analysis is performed for three optical and electrical methods of exciting space-charge waves in photosemiconductors: (i) excitation by an external ac electric field combined with a static interference pattern, (ii) excitation by a moving interference grating, and (iii) excitation by an oscillating interference grating. It is shown that, in the case when space-charge waves are excited using a combination of all three methods, the dependence of the direct current passing through a sample on the excitation frequency exhibits two peaks that correspond to the resonant excitation of two modes of space-charge oscillations, namely, drift waves and trap recharging waves. It is noted that experimental observation of the peak attributed to the excitation of trap recharging waves should not pose any problems, whereas observation of the second peak associated with the excitation of drift waves is significantly complicated because of the small magnitude of the effect, especially for materials with a low electrical conductivity (or a long Maxwell relaxation time).