Magnetostatic Wave Propagation Research Articles

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.

Hysteresis of the characteristics of magnetostatic waves in ferrite films with stripe domains whose magnetization vectors are oriented close to the plane of the film

The propagation of zero-exchange spin waves (magnetostatic waves) is investigated in yttrium iron garnet films having a regular stripe domain structure with almost in-plane orientation of the domain magnetization vectors. The characteristics of the waves are studied for magnetizations of the film parallel and perpendicular to projections of the [111] crystallographic axes onto the plane of the film. It is established, in contrast with films having the domain magnetization vectors oriented close to the normal to the plane of the film, that both the propagation of magnetostatic waves and the variation of the parameters of the domain structure exhibit a distinctly pronounced hysteretic character as the magnetizing field is varied. The hysteresis of the amplitude-frequency response, equiphase, and dispersion curves of the magnetostatic waves is investigated. The authors examine how the hysteresis of these parameters is related to the hysteresis of the domain structure. The spectrum of magnetostatic waves is found to have an interval of wavelengths (wave numbers) that are not excited in the unsaturated film when the applied field is close to the saturation value, and this phenomenon as well exhibits hysteresis.

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.

Auto-oscillation thresholds at the main resonance in ferrimagnetic films

The propagation of large-amplitude forward-volume magnetostatic waves (MSW's) is studied in ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ and $[\mathrm{BiLu}{]}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ thin films. The onset of auto-oscillations beyond the second Suhl instability influences the transmission characteristics of a MSW delay line. Global variations in transmitted power over a frequency-power input parameter space are monitored using density plots. There is a shift in the MSW passband with increasing input power that is explained by a decrease in demagnetizing field with an increase in dynamic magnetization. As the input power increases beyond a threshold value, we observe an increase in signal amplitude, heralding the onset of auto-oscillations. Fingers of auto-oscillation spanning an input range of 200 MHz and 10 dB are formed. The locations of these fingers are correlated with the locations of spin-wave resonance notches in the MSW passband. The auto-oscillation thresholds in the vicinity of a spin-wave resonance notch are 4--8 dB lower than elsewhere in the passband. A heuristic model based on a reduced group velocity near a notch can explain the lower threshold values.

Feasible Conditions for Magnetostatic Wave Solitons

Feasible conditions for magnetostatic wave envelope (MSWE) soliton formation and propagation have been discussed by quantitatively investigating the decay features of MSWE solitons. A normalized model equation has been derived from the nonlinear Schrödinger equation to analyze the decay features of MSWE solitons in detail. With the normalized model equation, a numerical study on the amplitude decay characteristics of MSWE solitons and the broadening properties of their full-width at half maximum (FWHM) has been performed. The amplitude decay rate of MSWE wave packets has been found to be dependent on the input power level, so is the broadening rate of their FWHM, and it should be emphasized that the increase of input power has further been proved to have an effect on the damping of MSWE solitons which is equivalent to the decrease of loss.

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).

Propagation of magnetostatic waves in a ferrite plus high-T c superconductor structure in the presence of transport current in the superconductor

A thin-film structure consisting of a ferrite and a high-Tc superconductor was used to investigate the effct of the transport current in the superconductor on the amplitude-frequency characteristic and dispersion of surface magnetostatic waves (MSWs) in a ferrite film. It was found that the nature of energy transfer between the MSWs and the superconducting film undergoes a significant change as the transport current is varied. In particular, in one of the current ranges, energy can be transferred both from the MSWs to the superconductor and back again, whereas in another range it can only be efficently transferred to the superconductor.

Interaction between a ferromagnet and a high-temperature superconductor at the interface in thin-film heterostructures

The development of high-temperature superconductor (HTSC)/ferromagnet thin-film heterostructures is a promising direction in their application to spin-wave electronics. The state of the HTSC-ferromagnet interface determines the nature of the propagation of the surface magnetostatic waves in the heterostructure. The formation of the HTSC films in the heterostructures involves thermal treatment at high temperatures, which results in the diffusion interaction of the HTSC films and the ferromagnet. The heterostructure consists of a YBa2Cu3O7−x HTSC film deposited by pyrolysis on an Y3Fe5O12 ferromagnetic film grown epitaxially on a (111)-oriented gadolinum-gallium garnet Gd3Ga5O12 substrate. The interdiffusion is studied from the intensity distribution curves of the x rays of iron (Fe), barium (Ba), copper (Cu), and silver (Ag), the last introduced into the HTSC in the amounts of 5–50 wt.%. The thin-film heterostructures are studied in the microwave range. A correlation is found between the state of the interface and the microwave characteristics.

Magnetostatic wave propagation characteristics at low temperatures

Low temperature characteristics are studied for the linear and nonlinear magnetostatic wave (MSW) propagation in yttrium iron garnet (YIG) films theoretically and experimentally. It is confirmed that the saturation magnetization is the only factor which governs the propagation characteristics at low temperatures. Moreover, the ferromagnetic resonance (FMR) linewidth /spl Delta/H of a YIG film is measured from the propagation loss and delay of MSW, and it is found that the /spl Delta/H becomes larger at low temperatures.

Simulation of Magnetostatic Wave Envelope Soliton Propagation in Yttrium Iron Garnet Films

Although formation and propagation of magnetostatic soliton waves in YIG (yttrium iron garnet) films are attracting great attention, there has been no discussion about simulating soliton formation and propagation in YIG films from the viewpoint of circuit analysis and simulation. In this report, we propose a new algorithm to simulate the magnetostatic soliton wave output. We first describe the linear magnetostatic wave equivalent circuit model we have developed and then discuss the simulation algorithm, which combines the linear equivalent circuit model and the soliton wave solution of the nonlinear Schrödinger equation. The simulated results are in excellent agreement with reported experimental results. We also find that the proposed simulation is very effective to determine various physical parameters in the YIG film for given experimental conditions.

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.

Microwave excitations in Bi-doped garnet films

Garnet films of the series (Bi,Lu) 3(Fe,Mg) 5O 12, with Bi contents of 0.85/f.u., have been investigated using microwave techniques. The samples were 1.7–10 μm thick, and were grown under different conditions. The uniaxial anisotropy and the resonance linewidths were evaluated over the temperature range 4.2–300 K. The magnetostatic wave propagation losses in the interval 3–6 GHz were measured and correlated with the resonance linewidths and the sample growth conditions. For these samples the resonance linewidth maxima occurred at about 50 K. The minima of the propagation loss and the resonance linewidth were obtained for the film growth velocity υ = 0.88 μm/min. The processes of microwave soliton formation and propagation have been observed experimentally in these Bi-doped garnet films. Under the continuous-wave regime modulation instability was observed.

Magnetostatic wave characteristics control by light at the ferrite-semiconductor layer structure

This paper reports results of theoretical studies of magnetostatic surface wave (MSSW) propagation in a photosensitive semiconductor-ferrite layer structure while the external electromagnetic wave acts on the semiconductor surface. The photoelectromagnetic effect is included in the theory. The dispersion relation of MSSW has been found and the effects of various intensities of the electromagnetic wave on the propagation characteristics have been examined. Values for CdSe and yttrium iron garnet parameters were used for computer simulation. It has been shown that the MSSW propagation loss increases, the frequency range in which the MSSW exist narrows and the group time delay decreases by a factor of 3–4 with increasing the intensity of the external wave.

Tunable magnetostatic waves bandpass filters with scandium doped yttrium iron garnet films

This paper reports results of theoretical and experimental studies of microwave bandpass tuned filters based on magnetostatic surface wave (MSSW) propagation in yttrium iron garnet (YIG) films. Filter transmission and input impedance characteristics for saturation magnetization 139 kAm−1 of YIG films and 32 kAm−1 of scandium-doped YIG films have been calculated and measured experimentally. Structures of a planar, multilayer metal-dielectric-YIG geometry are used to model the filters. Parameters of the structures have been optimized with the help of a computer. Scandium-doped YIG films of thickness near 100 Μm and saturation magnetization 32 kAm−1 have been found potentially useful in the manufacture of tunable bandpass filters.

Effect of pulsed optical heating on magnetostatic wave propagation in ferrite film

The effective control of magnetostatic spin wave propagation in yttrium-iron-garnet films using illumination of the film with optical pulses has been demonstrated. Heating of the film by 17/spl deg/C followed by a decrease of the film magnetization of up to 13% was obtained for optical pulses with energy of 0.2 J and duration of 2-5 ms. Variation of the wave frequency by 55 MHz, change of the wave number by tens of percent, and increase of the wave delay time from 60 to 150 ns were observed. These effects may find applications in the development of optically controlled microwave devices.

Propagation loss of magnetostatic waves in single and multilayered waveguides

Davidenko’s method [Doklady Akad. Nauk, S.S.S.R. (N.S.) 88, 601 (1953)] is applied for determining the propagation losses of magnetostatic waves in single- and double-layered waveguiding structures. The phase and attenuation constants are directly obtained by solving coupled first-order ordinary differential equations in a dummy variable. Thus, iteration procedures are not necessary. The propagation losses for homogeneous single yittrium-iron-garnet YIG film structure have been calculated for three principal modes of magnetostatic waves. In the case of a double-layered structure, the dependence of propagation losses on the separation between the films and the effect of linewidth of the films in inhomogeneous waveguides have been investigated for magnetostatic surface wave propagation.

Theory of bistable magnetostatic surface waves

A comprehensive theory of nonlinear magnetostatic wave propagation in a corrugated ferromagnetic film is presented. The applied magnetic field is in the plane of the film, and is perpendicular to the propagation direction. A portion of the film has its upper boundary periodically corrugated, and an analysis close to the Bragg condition is carried out. Typical bistable loops of output power against input power are obtained. Multistability is predicted for input powers, in the range 50-150 mW/mm. The threshold power is rather sensitive to the modulation of the upper surface, i.e., to the amplitude of the geometric variations on the periodic surface. Small amplitudes suppress the multistability and this critical region is investigated quantitatively. It is concluded that the multistable effects should be readily observable. >

Anisotropic propagation of magnetostatic surface waves in a nonstationary magnetized ferrite film

Propagation of magnetostatic surface waves (MSSWs) in a yttrium-iron-garnet (YIG) film placed in an external homogeneous slowly time-varying magnetic field was investigated theoretically in the geometrical optics approximation. The MSSW trajectories for the cases of amplitude and angular modulation of the magnetizing field were calculated. Anisotropic MSSW propagation in oscillating magnetizing field can be used for spectral analysis of microwaves. >

FMR of Multi-layered Magnetic Film LaYIG/GGG/LaYIG/GGG

1 Introduction Since single crystal magnetic films which have multiple layers with the same magnetization such as LaYIG/GGG/LaYIG film were first made by the authors, they have been widely used in microwave delay line with linear dispersion and other devices. Recently ferromagnetic resonance (FMR) and magnetostatic wave propagation characteristics of similar multi-layered film have been studied by many authors, whichris important for the multi-layered film to be used in microwave region. But until now many important characteristics of the multi-layered film have not been well understood. The direction and magnitude of uniaxial anisotropy effective field H_(11), the widening of FMR linewidth △H,

Numerical analysis and computer simulation of magnetostatic wave propagation in a YIG-loaded waveguide

Magnetostatic wave (MSW) propagation in a finite-width ferrite slab placed inside and along a rectangular waveguide is investigated theoretically and numerically. Using the integral equation method, the general solution to the problem of wave propagation is derived. Thin-slab approximation makes the derived solution more tractable and provided the dispersion relations in terms of an infinite determinant. From the results presented, it can be concluded that, in order to obtain a high value of group time delay over a large bandwidth, thin, narrow slabs placed in the center of the guide must be used. On the other hand, to maximize the device bandwidth, thin slabs placed at the top or bottom of the guide are most appropriate. >