Characteristics of the electromagnetic radiation resulting from arbitrarily directed propagation of magnetostatic surface waves in an increasing transverse magnetic field

Radiation of the electromagnetic waves accompanying propagation of a magnetostatic surface wave with nonparallel directions of the phase and group velocities in a ferrite slab magnetized in its plane by a transverse linearly increasing magnetic field is analyzed using the model of accelerated motion of magnetic charges. It is shown that, at each point of the space surrounding the ferrite slab, the shape of the radiation pattern strongly depends on the angle between the direction perpendicular to the direction of propagation of the magnetic field and the direction of the wave vector of the magnetostatic surface wave.     

双层YIG波导中静磁体波的传播特性

本文研究了在倾斜静磁场作用下,双层YIG薄膜波导结构中静磁体波的传播特性,得到了其色散的特征方程,计算了磁场倾角从5°到20°范围内双层波导结构中静磁体波传播的色散关系和延迟特性.结果表明,斜向场情况下在双层YIG薄膜结构中传播的静磁体波适合应用于高频范围,并且通过调节磁场倾角可以获得比单层膜波导结构更好的延迟率可调范围.斜向场情况下采用双层YIG薄膜结构,对于改进静磁波器件和磁光波导器件的性能具有十分重要的意义.     

Edge-Guided Magnetostatic Mode in a Ridged-Type Waveguide (Short Papers)

A ridged-type magnetostatic waveguide is analyzed using the boundary element method. A bias magnetic field is applied perpendicularly to the surface of an yttrium-iron-garnet (YIG) film grown on a gadlinium-gallium-garnet (GGG) substrate. The dispersion curves and the potential profiles obtained in this paper show that the mode has a strong nonreciprocal property and is a kind of edge-guided mode which propagates along either side of the ridge, depending upon the direction of the bias field and the direction of the wave propagation. In addition, the authors emphasize the fact that the boundary element method is useful for analysis of a complex structure in the field of magnetostatic wave (MSW) devices.     

Finite-element analysis of magnetostatic wave propagation in a YIGfilm of finite dimensions

A unified numerical approach based on the finite-element method is described for the magnetostatic wave propagation in a YIG film of finite dimensions. Both magnetostatic surface wave modes are treated. The validity of the method is confirmed by calculating the magnetostatic wave modes in a YIG-loaded rectangular waveguide and in a YIG film of finite width. The numerical results of a YIG films with nonuniform bias field along the film width are also presented, and the effects of bias field distributions on the delay characteristics and potential profiles are examined     

Finite-Element Solution of Planar Inhomogeneous Waveguides for Magnetostatic Waves

A unified numerical approach based on the finite-element method is described for the solution of planar inhomogeneous waveguides for magnetostatic waves. Both magnetostatic volume wave and magnetostatic surface wave modes are treated. The validity of the method is confirmed by calculating the magnetostatic wave modes of layered YIG films. The numerical results of inhomogeneous YIG films with alpha-power magnetization profile are also presented, and the effects of magnetization inhomogeneities on the delay characteristics and potential profiles for magnetostatic forward volume wave, magnetostatic backward volume wave, and magnetostatic surface wave modes are examined.     

Magnetostatic waves in the gap between two ferromagnetic films that move relative to each other

The propagation of a magnetostatic gap wave in a gap between two ferromagnetic films with opposite magnetizations is considered under the conditions for relative longitudinal displacement. When the velocity of one film is reversed, the transformation of spectra is similar to the transformation in which each spectrum of magnetostatic wave with corresponding symmetry is split into two branches. It is demonstrated that significant modification of the magnetic field distribution in the gap structure occurs when the film moves along the energy propagation direction of the gap-wave mode.     

外加偏置磁场对静磁波模式及其频带的影响

本文完整地展现了磁光薄膜中任意倾斜的外加直流偏置磁场对微波静磁波激发模式及其带宽的影响,实现了对不同静磁模的统一考虑,为进一步分析磁光Bragg器件的衍射性能提供理论基础.计算分析表明:(1)当外加偏置磁场的大小不变时,传统磁化情形下的静磁波带宽最大,此时基于MSBVW的磁光Bragg器件较相应的MSFVW器件有更高的工作频率;(2)在适当倾斜的偏置磁场作用下,静磁反向体波(MSBVW)、静磁正向体波(MSFVW)和静磁表面波(MSSW)均可被激发,它们的激发频率依次增大;(3)通过倾斜偏置磁场可使MSFVW的频带向高频移动.     

Dispersion of spin waves and magnetoelastic waves in YIG

Microwave pulse-echo experiments have been performed using YIG samples, and data are presented illustrating a variety of elastic, magnetoelasfic, and spin wave propagation phenomena. Both disks and rods of YIG were used, with excitation at X-band frequencies. The spin wave mode of propagation shows very strongly dispersive behavior when the spin wavelength is comparable to one of the sample dimensions. The group velocity is obtained from the magnetostatic mode spectrum of the appropriate configuration and is combined with the spatial variation of the internal magnetic field to compute the delay time. Exchange effects are important in the case of the disk and are included in the analysis. The agreement between theoretical and experimental delay times is quite satisfactory for all configuration.     

Effect of the Magnetic Perturbation on Magnetostatic Surface-Wave Propagation

This paper discusses the propagation of the magnetostatic surface wave in two ferrite slabs (namely, YIG and Ga-YIG) with different magnetic saturations, and considers a weak coupling in between them. The theoretical results are obtained by using the conventional perturbation technique which is subsequently supported by experiment. Further, the time delay in group velocity affected by the magnetic perturbation is treated theoretically.     

Behavior of the Magnetostatic Wave in a Periodically Corrugated YIG Slab (Short Papers)

An analysis for the propagation characteristics of the magnetostatic wave in a YIG slab having periodically corrugated surfaces is presented. The Brillouin diagrams, close to the intersection point (omega,K) of m = 0 and m = -1 space harmonics, are obtained for different slab thicknesses, and the nonexistence of leaky wave modes has been established. Some discussions concerning the internal dc magnetic field and the propagation loss are also presented,     

Surface waves on a uniaxial plasma slab--Their group velocity and power flow

The relation between group velocity and the velocity of energy transport for surface waves in plane-stratified, anisotropic, dispersive media, which was derived in [1], is verified by direct calculation for the case of surface waves on a uniaxial, cold plasma slab located in free space. A superimposed dc magnetic field of infinite strength and parallel to the interfaces generates the uniaxial anisotropy in the slab. Surface waves having an arbitrary direction of propagation with respect to the dc magnetic field are considered. A useful graphical presentation of the dispersion relation is given, from which the direction of propagation of "surface wave rays" is directly obtained.     

磁光薄膜波导中光导波的模式转换和衍射效率计算

根据耦合模理论,应用微扰方法分析了Ｂｉ：ＹＩＧ薄膜波导中斜向静磁场对静磁波与导波光相互作用的影响,计算了斯托克斯和反斯托克斯相互作用中导波光的模式转换效率和衍效率。     

Magnetostatic Wave Propagation in a Finite YIG-Loaded Rectangular Waveguide

The propagation of magnetostatic waves (MSW) in a waveguide partially loaded with a low-loss ferrite slab is investigated theoretically. The most common low-loss ferrite material used for MSW propagation is epitaxial yttrium iron garnet (YIG). A YIG slab is placed inside and along the guide and not in contact with the sidewalls of the wavegnide. The dc magnetic field is assumed to be parallel to the YIG slab and perpendicular to the direction of propagation. Using the integral equation method, the dispersion relation is found to be an infinitely large determinant equal to zero. Proper truncation of this determinant and numerical analysis to find its roots are carried out in this work. It is seen that in order to obtain high values of group time delay, the YIG slab must be narrow and placed at the bottom of the guide. On the other hand, to maximize the device bandwidth, a narrow YIG slab positioned at the top inside surface of the waveguide is preferred. It is also noticed that there exists a tradeoff between the time delay and the device bandwidth and that maximization of one property leads to a poor value in the other. Thus, some design compromises should be made. It is also observed that the frequency range of operation of the device can be adjusted by an external magnetic bias field. This property of tuning the device to operate in any frequency range adds an extra dimension of flexibility to the operation and also to the design of these devices.     

Anisotropy Characteristics of Magnetostatic Surface Wave Propagating in YIG/Dielectric/Metal Layered Structure

The anisotropy of magnetostatic surface wave (MSSW) propagating in finite width YIG/dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell equation and the appropriate transmission Green's function matrix (G). From the relationship of Green's function matrixes of dielectric layer and ferrite layer, the dispersion equation is obtained.The MSSW filter is designed to verify the dispersion characteristics. The experiment results are in good agreement with the calculating data from the model.     

Magnetic Wave Interactions in a Periodically Corrugated YIG Film

The magnetic wave interactions in a YIG film having periodically corrugated surfaces are investigated for the ease of magnetization parallel to the propagation direction. By a singular boundary perturbation procedure, the coupled-mode equations governing the nature of the interactions are deduced and analyzed to obtain the characteristics of the interactions. Representative numerical results are presented to reveal the characteristics of the resulting wave filter.     

Propagation characteristics of the magnetostatic surface wave inthe YBCO-YIG film-layered structure

Propagation characteristics of the magnetostatic surface wave (MSSW) in a YBa₂Cu₃O_7-x (YBCO)-yttrium iron garnet (YIG) multilayered structure are investigated. Effects of the superconductor on the MSSW are discussed with regard to the dispersion characteristics of both the phase and attenuation constants as a function of the air gap, between YIG and YBCO, taking into consideration the magnetic line-width of the YIG film. It was found that the nonreciprocity of MSSW is enhanced significantly by the superconductivity and depends on the magnetic line-width of the YIG film. To examine the effect of a YBCO on the MSSW propagation, experiments are carried out using a commercially available YIG film. Magnetic losses at low temperature are briefly discussed with experimentally observed nonreciprocity     

Magnetic Waves Guided by a Linearly Tapered Yig Film

A quasi-optical treatment is given for the dispersion relation and the group delay time of a magnetic wave guided by a YIG film having a weak linear taper in its thickness in the propagation direction of the guided magnetic wave. This treatment has 1) confirmed the intuitive results in which the local value of the thickness is used for the tapered film, 2) indicated the frequency regions of validity of the intuitive results, and 3) revealed interesting features of the wavenormal and ray directions inside a YIG film.     

Control of magnetostatic waves in thin films by means of spatially nonuniform bias fields

Although magnetostatic wave devices normally employ spatially uniform magnetic bias, control of important features of the modes is afforded through judicious use of dc field gradients. Such control can be the basis for new forms of microwave signal processors.Gradients in either the field magnitude, direction, or both can be employed to affect wave dispersion or mode spectra. This is done to control prespecified characteristics such as frequency, rf energy distribution, impedance, and the velocity of energy propagation.Very general mathematical analyses of both the forward volume wave and surface wave geometries are developed for cases where the effective magnetic bias has, depending upon the mode, transverse spatial variation along either the ferrite film width or thickness caused by the applied field, saturation magnetization, magnetic anisotropy — or some combination.Computer simulation has been used to obtain eigenfrequencies and eigenmodes when the bias is uniform or nonuniform. The latter cases reveal that a great deal of control over the mode energy distributions can be exercised by the proper choice of gradients. For example, a forward volume wave can be forced to have strong field-displacement characteristics that are either nearly reciprocal or very strongly nonreciprocal.This research was supported, in part, by the Joint Services Electronic Program (JSEP) under Contract DAAG29-83-K-0003 administered by the Research Laboratory of Electronics (RLE); the National Science Foundation under Grant 8008628-DAR; and STAS 0356 administered by the Battelle Research Triangle Park Office.     

New nonlinear magnetostatic surface waves in a ferromagnetic (YIG)

The general propagation characteristics of magnetostatic surface waves guided by a single interface of a semi-infinite nonlinear dielectric cover and a ferromagnetic substrate (YIG) have been derived. The nonlinear dielectric cover has intensity dependent refractive indices. The magnetostatic approximation is considered and retardation is ignored in describing the electromagnetic fields in the structure. The used magnetostatic approximation is leading to new waves and might be called nonlinear magnetostatic surface waves. The propagation of these waves is non-reciprocal in contrast to the linear magnetostaic surface waves, which had been only found in the negative direction of propagation.     

Microwave diplexer using magnetostatic surface and backward volume waves

An experimental diplexer based on magnetostatic wave propagation in a tangentially magnetised thin film of YIG is reported. The diplexer function is obtained by using the fact that magnetostatic surface and backward volume waves propagate in contiguous but nominally nonoverlapping frequency bands.