On the Modified Resonance Theory of Waveguide Circulator with Various Ferrite Specimens

A modified resonance theory of waveguide circulator with ferrite specimen is presented. The kernal of this theory is a two-step analysis method of an H-plane Y-junction waveguide circulator. For the first step, the ferrite specimens of Y-junction waveguide circulators are treated as if it were dielectric resonators with no magnetic bias. This simplistic approach is used to design the ferrite specimens of the circulators. Simple formulas are developed for determining the center frequency of the circulators. For the second step, wave circulation is made possible when a pair of degenerate resonance modes experiences different changes when the ferrite specimens are being magnetized. A modified analysis of joint resonance theory and simple field theory is advanced to evaluate the performances of the circulators. Good agreements between the analytically obtained performance and experimental result of various MMW waveguide circulators are observed.     

Circular waveguide with azimuthally magnetized. Gyrotropic medium

An equation has been derived for determining propagation constants in a circular waveguide with azimuthally magnetized bigyrotropic filling. A computer was used to study the dispersion properties, electromagnetic field structure, and distribution of the components of the Poynting vector over the waveguide cross section in the case of a ferrite filling described by a permeability tensor with unequal diagonal components.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 10–15, June, 1978.     

Electromagnetic oscillations in a rectangular waveguide with a transversely magnetized ferrite plate

The complex propagation constant in a rectangular waveguide with a transversely magnetized ferrite plate has been found by a numerical calculation. The magnetic properties of the ferrite medium are described by the standard permeability tensor for a polycrystalline ferrite, having real and imaginary parts. The solutions are given as curves on the complex propagation-constant plane. The parameter is the relative magnetizing field, which varies over a wide range including a ferromagnetic resonance. From the family of curves obtained for various relative magnetizations and damping parameters, one can quantitatively evaluate the relation between the types of oscillations. This relation depends on the position of the ferrite plate in the waveguide and on the dielectric constant of the ferrite as well as on the magnetization and damping constant.Translated from Izvestiya VUZ. Fizika, No. 4, pp. 74–81, April, 1970.     

Waveguide interaction of light with spin waves in a ferromagnetic film

We discuss the results of a theoretical analysis of the waveguide interaction of light and spin waves. Both linear and quadratic magnetooptical effects are taken into account. The features of the interaction are considered for the three principal types of spin waves: waves in a normally magnetized ferromagnetic film, and longitudinal and transverse waves in a tangentially magnetized film. Isotropic and anisotropic diffraction processes are considered. Numerical estimates of the intensity and frequency properties of the diffraction scattering are given for a number of situations of practical interest. The effect of a strong constant magnetic field on the interaction of light and spin waves is considered.Translated from Izvestiya Vyssnikh Uchebnykh Zavednii, Fizika, No. 4, pp. 5–31, April, 1989.     

Effects of magnetic field and temperature on the nonrelativistic bremsstrahlung process in magnetized anisotropic plasmas

The magnetic field and thermal effects on the nonrelativistic electron-ion bremsstrahlung process are investigated in magnetized anisotropic plasmas. The effective electron-ion interaction potential is obtained in the presence of an external magnetic field. Using the Born approximation for the initial and final states of the projectile electron, the bremsstrahlung radiation cross section and bremsstrahlung emission rate are obtained as functions of the electron energy, radiation photon energy, magnetic field strength, plasma temperature, and Debye length. It is shown that the effects of the magnetic field enhance the bremsstrahlung radiation cross section for low plasma temperatures and, however, suppress the bremsstrahlung cross section for high plasma temperatures. It is also shown that the magnetic field effects diminish the bremsstrahlung emission rate in magnetized high temperature plasmas.     

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)     

Parametrically stimulated recovery of a microwave signal stored in standing spin-wave modes of a magnetic film

We demonstrate that a microwave signal carried by a packet of dipolar spin waves propagating in a tangentially magnetized magnetic film can be stored in the form of standing dipole-exchange spin-wave modes of the film and can be recovered by means of a double-frequency parametric pumping mechanism. This mechanism is based on the parametric amplification of the standing (thickness) modes of the film by external pumping. The time of recovery, duration, and power of the recovered pulse signal are controlled by the power of the pumping signal.     

圆柱状铁磁体中的偶极-交换自旋波

对于轴向磁化的圆柱状铁磁体,同时考虑偶极作用和交换作用,得到了偶极-交换自旋波的本征方程,给出了频谱的数值结果。当自旋波波矢β较小,即偶极能起主要作用时,相当于静磁模的结果,β较大,即交换能起主要作用时,过渡到宏观自旋波交换模理论的结果。     

Two-magnon relaxation reversal in ferrite spheres

The reversal of two-magnon relaxation associated with linear scattering of oscillations of uniform magnetization precession from sample nonuniformities is studied theoretically and experimentally in ferrite spheres of yttrium iron garnet (YIG). Relaxation reversal is performed by parametric phase conjugation of dipole-exchange spin waves formed as a result of scattering of uniform precession from inhomogeneities. As a result of two-magnon backward scattering of dipole-exchange spin waves with a certain time delay, magnetization oscillations are renewed with an amplitude that could exceed the initial amplitude of uniform precession. The relaxation reversal is due to crystallographic anisotropy of the sample and is manifested most strongly when a YIG sphere is magnetized along the intermediate axis [110]. Experiments were carried out on YIG spheres of diameter 0.65–1.05 mm for a parallel pumping frequency ω _p /2π ≈ 9.4 GHz, which is about twice the uniform precession frequency. The maximal delay time for the restored signal of uniform precession was about 2 μs, while the maximal amplitude exceeded the initial uniform precession amplitude by a factor of about 5. The “latent” relaxation parameters of ferrites, e.g., the natural ferromagnetic resonance linewidth associated with many-particle processes and the linewidth associated with two-magnon scattering at bulk nonuniformities, are determined experimentally.     

On polarized neutron scattering from magnetized samples and the spin echo effect

The scattering of polarized neutrons from magnetized samples is considered in the general case of arbitrary orientation between the incident polarization, the magnetic field of the sample and the polarization of the scattered neutrons. Including both nuclear and magnetic scattering the general expressions for the cross section and the polarization of the scattered beam are derived in the case of small-angle scattering. It is shown that under certain experimental conditions an effect analogous to the Neutron Spin Echo should be observed, which could be used to measure small energy transfers. The contribution arising from the scattering by spin waves is examined in detail.     

磁化铁氧体材料电磁散射递推卷积-时域有限差分方法分析

根据递推卷积原理，将磁化铁氧体材料的频域磁导率过渡到时域，通过引入时域复数磁化率张量和时域复数磁感应强度矢量，提出了磁化铁氧体材料电磁散射的三维时域有限差分方法.为了验证该方法，用它计算了磁化铁氧体球的后向雷达散射截面，与文献结果符合很好.计算结果表明，该方法是分析磁化铁氧体材料电磁散射一种可行的方法. 关键词： 递推卷积 磁化铁氧体 电磁散射 时域有限差分方法     

含有铁氧体圆杆的矩形波导的散射矩阵及其等效线路

本文尝试用四端网络法研究非互易微波铁氧体器件。首先,把一节含着一根铁氧体杆的三厘米波段的矩形波导看作四端网络,进行阻抗和散射系数的测量。由测得的散射矩阵求出了T形等效线路,结果表明,小直径铁氧体杆具有并联容性电纳的性质,电纳的数值随外磁场的变化范围很大,与可调螺钉的作用十分相似。其次,把两根铁氧体杆沿波导纵向排列,在实验中考察了这种相继阻碍物的等效线路,结果表示,只要相邻阻碍物的距离足够大,总的等效线路可用“单元”等效线路的串联表示。最后,以分析相移网络为例,说明了等效线路的应用。用这一方法研究波导中的多体散射,具有独特的优点。     

Spin-wave quantization in ferromagnetic nickel nanowires

The dynamical properties of uniform two-dimensional arrays of nickel nanowires have been investigated by inelastic light scattering. Multiple spin waves are observed that are in accordance with dipole-exchange theory predictions for the quantization of bulk spin waves. This first study of the spin-wave dynamics in ferromagnetic nanowire arrays reveals strong mode quantization effects and indications of a subtle magnetic interplay between nanowires. The results show that it is important to take proper account of these effects for the fundamental physics and future technological developments of magnetic nanowires.     

有限磁场中等离子体圆柱波导的传播特性

分析了有耗介质中等离子体圆柱波导在有限外加磁场中的传播特性.重点讨论了波导传播常数随等离子体参数、介质参数和外加磁场的变化.分析结果表明，有限强磁场中的等离子体波导的传播特性比无外磁场或外加磁场为无穷大时具有更强的控制能力. 关键词：     

磁化铁氧体电磁散射的移位算子FDTD分析

将移位算子（shift operator,SO）-时域有限差分（fintie difference time domain,FDTD）方法推广到外磁场沿任意方向时磁化铁氧体的情形.从磁化铁氧体的相对磁导系数张量和各向异性情形下Maxwell旋度方程出发,推导出外磁场沿任意方向情形下磁化铁氧体电磁散射的SO-FDTD迭代公式.应用该方法计算了磁化铁氧体层、磁化铁氧体球及含磁化铁氧体涂层的Von Karman形雷达罩电磁散射,数值计算结果表明了该算法的正确有效性. 关键词： 磁化铁氧体 FDTD 移位算子法     

Scattering characteristics of conducting cylinder coated with nonuniform magnetized ferrite

An analytical technique, referred to as the scattering matrix method （SMM）, is developed to analyse the scattering of a planar wave from a conductolution for the nonuniform fering cylinder coated with nonuniform magnetized ferrite. The SMM srite coating can be reduced to the expressions for the scattering and penetrated coefficients in four particular cases： nonuniform magnetized ferrite cylinder, uniform magnetized ferrite-coated conducting cylinder, uniform ferrite cylinder as well as homogeneous dielectric-coated conducting cylinder. The resonant condition for the nonuniform ferrite coating is obtained. The distinctive differences in scattering between the nonuniform ferrite coating and the nonuniform dielectric coating are demonstrated. The effects of applied magnetic fields and wave frequencies on the scattering characteristics for two types of the linear profiles are revealed.     

Magnetic excitations in solids

This article presents a review of low to moderate frequency magnetic excitations, termed magnons or spin waves, in magnetically ordered materials. The emphasis is on intuitive behavior rather than analytical theory. Topics include spin waves, magnetostatic modes, dipole-exchange modes, surface anisotropy, dispersion properties, nonlinear effects, and relaxation. These phenomena are illustrated with experimental examples based on magnon light scattering results as well as conventional microwave techniques.     

TE10矩形波导中填充金属线阵和铁氧体合成的新型左手媒质

在TE₁₀矩形波导中填充金属线阵和铁氧体合成了一种新型的左手媒质结构.分别使用了转移函数矩阵方法以及全波仿真工具Ansoft HFSS对所提出的结构进行了分析.结果表明,在横向磁化铁氧体等效磁导率实部为负的频段范围内,该合成结构呈现左手通带特性并伴随着后向波的传播现象.由于横向磁化铁氧体的等效磁导率为负的频段范围可调,故所提出的结构具有左手通带范围可调的特性. 关键词： 左手媒质 10矩形波导')" href="#">TE₁₀矩形波导 金属线阵 铁氧体     

Multiwave interactions of dipole-exchange spin waves in ferromagnetic films

Equations are derived for the slowly varying amplitudes in multiwave interaction of dipole-exchange spin waves in ferromagnetic films. A numerical estimate is provided for the efficiency of four-wave inversion of a spin-wave front in a normally magnetized film.St. Petersburg Electrical-Engineering Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 6/7, pp. 511–524, June–July, 1992.     

任意磁化方向铁氧体电磁散射时域有限差分分析的Z变换方法

利用坐标系转换矩阵给出实验室系中饱和磁化铁氧体的频域磁化率张量, 采用部分分式展开方法通过Z变换得到磁化率张量的Z域形式, 给出了任意磁化方向铁氧体电磁散射的Z变换-时域有限差分算法. 计算了饱和磁化铁氧体球的同极化和交叉极化后向雷达散射截面, 结果表明了算法的正确有效性. 关键词： Z变换 饱和磁化铁氧体 电磁散射 时域有限差分方法