Magnetostatic Waves In Ferrite Films Research Articles

Electrodynamic theory of multiport structures using magnetostatic waves in ferrite films and its applications

The paper presents an electrodynamic analysis of tunable multiport ferrite-dielectric structures with parallel transmission lines of an arbitrary type, coupled through propagating magnetostatic modes of magnetized multilayered ferrite films. The structures are supposed to be excited at one port by an incident electromagnetic wave, and amplitudes and phases of electromagnetic waves at other ports are obtained by an analytical procedure. The model holds for an arbitrary direction of a magnetizing field and describes the interaction of magnetostatic modes in ferrite films of a finite width. The solution is obtained in a self-consistent approach, i.e., a reaction of magnetostatic waves (MSWs) on transducers, which excite them, is taken into account. Derived closed-form expressions for response functions of multiports provide the base for the modeling of a wide class of MSW devices: multichannel adjustable filters and delay lines, directional couplers, frequency-selective power dividers, tunable oscillators and active filters, and multiport resonators. The theory is also valid for the analysis of multi-element, interdigital, and meander MSW transducers. Applications of a general theory are demonstrated for numerical calculations of frequency responses of surface and forward volume MSW filters, delay lines with new types of strip-line transducers (two-port and T-type), and for the analysis of a phenomenon of mutual coupling of transducers in conventional devices.

Excitation and Reception of Electromagnetic, Magnetostatic and Spin Waves in Ferrite Films

The paper presents a new universal formulation of electromagnetic fields in microwave ferrite-dielectric waveguiding structures from the given magnetic field distribution of an external source. The solution is derived from the linearized Landau-Lifshits equation using an orthogonality condition for eigenwaves of a magnetization. The magnetization excited in ferrite is obtained in an electrodynamic, magnetostatic or dipole-exchange approximation, depending on the approximation used for eigenwaves. Results are applied for the formulation and the analytical solution of self-consistent electrodynamic problems of an excitation and a reception of waves in ferrite films by transmission lines of an arbitrary type. Numerical calculations are performed for filters and delay lines on the base of symmetric strip-lines using surface and forward volume magnetostatic waves in ferrite films.

Excitation and Reception of Electromagnetic, Magnetostatic and Spin Waves in Ferrite Films - Abstract

The paper presents a new universal formulation of electromagnetic fields in microwave ferrite-dielectric waveguiding structures from the given magnetic field distribution of an external source. The solution is derived from the linearized Landau-Lifshits equation using an orthogonality condition for eigenwaves of a magnetization. The magnetization excited in ferrite is obtained in an electrodynamic, magnetostatic or dipole-exchange approximation, depending on the approximation used for eigenwaves. Results are applied for the formulation and the analytical solution of self-consistent electrodynamic problems of an excitation and a reception of waves in ferrite films by transmission lines of an arbitrary type. Numerical calculations are performed for filters and delay lines on the base of symmetric strip-lines using surface and forward volume magnetostatic waves in ferrite films.

Influence of cubic anisotropy on the temperature characteristics of magnetostatic waves in ferrite films magnetized in the film plane

Expressions for the temperature coefficients of frequency for magnetostatic waves in tangentially magnetized ferrite films having cubic anisotropy are obtained and analyzed. It is shown that in cases where the cubic axis lies in the plane of the film, temperature-induced changes in both the magnitude and direction of the external field can be used for thermostabilization of the frequencies. The problem of two-frequency thermostabilization is considered. The results of experimental investigations of the temperature characteristics of magnetization waves in a tangentially magnetized film of yttrium iron garnet with a {100} surface are presented.

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.

Nonlinear Diffraction of Magnetostatic Waves in Ferrite Films

Two-dimensional nonlinear diffraction of magnetostatic waves (MSW) in ferrite films is studied numerically using the model of nonlinear parabolic equation. This equation is derived by a new method from a bilinear relation similar to the Lorentz lemma. It is shown, that in the framework of this model the evolution of two-dimensional backward volume MSW pulse leads to a collapse in the case of an infinite film, while in a film waveguide of a finite width the collapse can be avoided, and the pulse amplitude can be stabilized. Dynamics of modulation instability of both backward volume and forward volume MSW under continuous excitation is also investigated.

Nonlinear magnetostatic waves in ferrite films in an inhomogeneous magnetic field

Surface magnetostatic waves of finite amplitude propagating in a ferrite film placed in a transversely inhomogeneous magnetic field are investigated theoretically. The bias field inhomogeneity makes the frequency range of the surface wave wider. The wave dispersion and frequency band for the lowest mode depend essentially on the wave amplitude.

Convolution of magnetostatic waves in ferrite films

Convolution of magnetostatic and electromagnetic waves (MSW and EMW) is considered. The following cases are presented: (1) three-wave interactions of MSW with EMW of microwave or optical range; (2) the interaction of MSW with excitation of the oscillation at sum frequency, that is not the own mode of the ferrite film.

The magnetostatic waves in ferrite film with losses

The influence of relaxation processes on dispersion equation solutions for surface and volume magnetostatic waves (MSW) propagating in a ferrite film is theoretically investigated. It is shown that dissipation is the main reason for the appearance of complementary MSW branches in frequency intervals which adjoin standard branches in spectra. The existence of threshold MSW wave numbers which upper bound the spectra of possible wave numbers is established. Asymptotic frequencies anf frequencies corresponding to the threshold values of wave numbers are calculated. The effects of dissipation on the ranges in which MSW exist are calculated. The frequency dispersion of the loss spectra is also calculated. >