Unidirectional information transport is often realized in magnonic application using the filters, isolators, and circulators. In this Letter, we propose the simple design of the unidirectional magnonic coupler, which is realized as a laterally coupled yttrium–iron–garnet waveguide coated with a metal layer. We experimentally discover and numerically confirm that the proposed structure can exhibit unidirectional coupling, which can be easily controlled by the direction of the external magnetic field. At the same time, we show how the dynamic magnetization profile of the spin wave is varied with the change in the propagation direction to the opposite along the coupler. Brillouin light scattering reveals the variation of the spatial spin-wave profile, which is then used to extract the value of the coupling length. The experimental results are in good agreement with the results of the coupling length estimation from two methods: eingenmode analysis and Landau–Lifshits–Gilbert solution in parallel with the Maxwell equations. This opens up alternative ways to fabricate the non-reciprocal magnonic devices. In particular, we consider the operation of the unidirectional magnonic coupler as a multi-regime logic device.

We propose the design of single-layer, double-layer, and triple-layer configurations of magnonic ring couplers, which perform spin-wave mode filtering and provide interlayer signal transmission in threedimensional architectures of magnonic integrated circuits. We study the characteristics of spin-wave dynamics in coupled magnonic structures with a ring resonator in planar and vertical configurations using Brillouin light scattering and the micromagnetic simulation method based on numerical solution of the Landau-Lifshitz-Gilbert equation. The mechanisms of backward and forward coupling control of spin-wave transport in yttrium iron garnet stripe placed in the proximity of the magnonic microring resonator are elucidated. The possibility of reversing the direction of spin-wave propagation with simultaneous selection of transverse spin-wave modes is demonstrated. It is shown that, in the proposed structure, multistream selection of a spin-wave signal is possible due to spatial frequency and simultaneous mode separation. Lateral and vertical magnonic rings could be used for magnonic logic application with the variation of the phase and amplitude of signals. We also demonstrate that the spin-wave mode order is an additional parameter that can be used to simultaneously control the transmission of the ring coupler with the facility to encode the logical state "0" or "1" with the width mode order. The multistream selection of a spin-wave signal and the spatial frequency and simultaneous mode separation lie behind the application of the proposed magnonic ring coupler as a multiport interconnection element and/or functional logical unit in reconfigurable integral blocks of magnonic networks.

A study of spin wave spectra in a two-layer structure of iron-yttrium garnet (YIG) with different magnitudes of the saturation magnetizations of the layers has been carried out. Different modes of spin wave propagation (reciprocal, nonreciprocal, single-wave) depending on the type of structure and width of the central waveguide are investigated. The classification of spin wave spectra is carried out, and the class of guided, outgoing, and edge spin modes is identified. In particular, it is shown that in a system of planar magnetic comb-type LS-type (Ms1 Ms2) microwave guide tubes with periodic boundary conditions, two non-contiguous frequency regions of existence of guided modes of the central waveguide are observed for a width w of the central waveguide. Two adjacent frequency regions exist in the system of planar magnetic comb-type HS-type (Ms1 Ms2) microwave guide tubes at any values of the width of the central waveguide: in the high-frequency region, the mode with outflowing modes of the structure is realized, while in the low-frequency region, the mode with guided modes of the central waveguide is realized. It is shown that in systems of both types in the region of strongly inhomogeneous magnetic fields there can exist modes of boundary waves having a mutual character of propagation. The results obtained can be used to expand and clarify the physics of wave processes in complicated magnetic structures.

Here we report recent data on the phenomenon of total nonreflection of spin waves (NRSWs). Using space- and phase-resolved Brillouin light scattering we experimentally studied the amplitude, direction, and phase of the NRSW in yttrium iron garnet films with artificial defects---an antidot array. An NRSW in the form of a focused beam of high intensity with the group velocity pointing along the line of defects is observed only for a critical angle between spin-wave phase velocity and an antidot array direction in a magnetic field. It is shown that the NRSW is an independent noncollinear spin wave arising as a result of the anisotropic nature of the propagation of surface magnetostatic spin waves in a magnetic medium. The numerical simulations agree well with experimental data. Micromagnetic simulations performed let us elucidate the phenomenon of the NRSW and map the spin-wave profile of dynamic magnetization inside the NRSW. The estimated mean free path of the NRSW reaches about 1 mm in the yttrium iron garnet film with a thickness of a few micrometers. These results demonstrate a unique approach to focusing and enhancing spin waves in magnetics through the use of artificial defects.

Here we present the nonreciprocal propagation of caustic beams and channeling of the backward volume spin wave in an yttrium-iron-garnet structure with the longitudinal symmetry axis and broken translational symmetry. The experimental method of Brillouin spectroscopy and the numerical micromagnetic methods are used to study the mechanisms of control of the nonreciprocal spin-wave signal propagation in a Tshaped junction with a partially metallized surface. It is shown that the partial metallization of the surface together with the reversal of the magnetic field direction can serve as a way to control the propagation of spin-wave beams. The formation of the spin-wave channel between the metal stripe and the edge of the magnetic film is observed experimentally and demonstrated by numerical solution of the Landau-LifshitzGilbert equation and Maxwell's equations. The proposed theoretical analysis explains the experimental results and provides useful technical information for the fabrication of reconfigurable magnonic devices, which utilize the spin-wave beam formation in the region of the junction of the magnonic waveguides with different widths. The proposed structure can be used as a functional element of signal branching and/or power division in magnonic networks and signal-processing devices based on them.

We investigated a spin-wave propagation in a magnon-crystal structure formed from two lateral microwaveguides separated by a one-dimensional antidot array. The mechanisms of control of the backpropagating regime of the surface spin waves both with geometry tuning and with power level variation in the case of in-plane magnetization are investigated by the method of micro-magnetic modeling and the experimental method of Brillouin light scattering spectroscopy. It was shown that for the case of spin-waves propagation through the isolated channels the shape anisotropy in the coupling region can be tuned effectively by a variation of the distance between the channels. The regime of nonlinear switching of the signal and backward propagation was observed in microwave and Brillouin spectroscopy measurements. The proposed effect of the signal separation manifests itself in the spatially and frequency-selective regimes of spin-wave propagation. Proposed spin-wave coupler opens an alternative way for the design of the functional interconnections of spin-wave based units in the planar magnonic networks.

Here, we report the results of strain-controlled spin-wave propagation regimes in a double-period multiferroic structure. It consists of an alligator-type magnonic crystal with a period of 250 μm and a piezoelectric layer, featuring a periodic counter-pin-type electrode system with a period of 125 μm. Employing microwave measurements, we acquired the transmission and dispersion of spin waves under various external electric field configurations applied to the piezoelectric layer. The formation of bandgaps in the magnon spectrum and the variation of the spin-wave transmission when altering the configurations of the external electric field are demonstrated. A finite element method reveals that the combination of the non-uniformity in the initial internal magnetic field of the magnonic crystal, which is caused by the presence of periodic alligator-type regions, together with elastic deformations, heightens the amplitude of the modulation of the internal magnetic field. Micromagnetic modeling has demonstrated that this modulation enhancement results in the variation of the spin-wave transmission at the frequency of the magnonic bandgap center of the magnonic crystal. The proposed design of the reconfigurable magnonic crystal creates a condition for the nucleation of the spin-wave bandgap, with further enhancement of the spin-wave reflection from the periodic grating induced by strain. We demonstrate the potential use of the proposed device as a multi-band NAND/NXOR spin-wave based logic gate.

We report on the spin-wave propagation along a magnonic waveguide with a local area of decreased magnetization, which is induced by heating produced with a focused laser spot. A phase-sensitive Brillouin light scattering technique is used to image how the spin wave propagates along the waveguide with a local heat landscape. Frequency-selective signal propagation along the waveguide is demonstrated. Micromagnetic simulations reveal intermodal interference variation in the region after the heated area. The proposed way to reconfigure the magnetization landscape can be used in magnonic devices with frequency-selective spin-wave transport.

We report on the coupling of spin waves propagating as guided modes of yttrium iron garnet stripes. Three stripes are placed parallel to each other and separated by gaps that are small enough to provide nearest-neighbor coupling. We term this geometry ``bilateral stripes.'' The origin of the coupling is the long-ranging dynamic, stray (dipole) field of the precessing magnetization vector. We propose controlling characteristics of this coupling through variation of the static magnetization angle with respect to the main axes of the geometry. We verified the functionality of the proposed magnonic coupler with a micromagnetic simulation of spin-wave propagation along the bilateral stripes. The micromagnetic numerical simulation yielded spectra of transmission of spin waves through the device prototype. Analysis of those spectra revealed that the bilateral stripes can be used as a functional unit in planar magnonic networks---they can be employed as a directional coupler, spin-wave multiplexer, or microwave power divider. Using Brillouin light scattering spectroscopy, we experimentally demonstrated spin-wave transport along the bilateral stripes. We were able to control the spin-wave routing between the stripes (``magnetic channels'') by varying the angle of the bias magnetic field.

The present work is devoted to the study of the optically induced formation of the band structure of a magnon crystal consisting of a ferrite microwave diode loaded with a semiconductor with periodic thickness modulation. Using the Brillouin light scattering method, it is demonstrated that an increase in the power of laser radiation illuminating the semiconductor layer leads to the formation of non-transmission bands in the spectrum of surface magnetostatic waves (PMSW) with a simultaneous increase in the central frequency of these bands. Using the finite element method, we connected the formed non-transmission bands with the Bragg resonances of the periodic structure, and also evaluated the effect of changes in the density of semiconductor electrons on the dispersion dependences and non-reciprocal properties of PMSV in such a structure.

The dynamics of spin waves during their multimode propagation in a magnonic crystal, which is an irregular narrow ferrite waveguide with periodic boundary modulation, has been studied by the method of Mandelstam--Brillouin spectroscopy. The transformation of the mode composition of spin waves propagating in an irregular ferrite waveguide is shown. The space-time dynamics of spin waves and the characteristics of the band gaps of a magnonic crystal are experimentally studied, and the possibility of controlling the frequency-selective properties of such a structure is shown. By excitation of a superposition of even or odd width modes of the ferrite microstructure, it becomes possible to control the position of the band gaps of a magnonic crystal. The results of the experiment agree with the results of micromagnetic modeling of the propagation and transformation of the spectrum of spin waves propagating in a ferromagnetic periodic structure. Keywords: spin waves, magnonics, magnonic crystal, micromagnetic modeling.

The dynamics of spin waves during their multimode propagation in a magnonic crystal, which is an irregular narrow ferrite waveguide with periodic boundary modulation, has been studied by the method of Mandelstam-Brillouin spectroscopy. The transformation of the mode composition of spin waves propagating in an irregular ferrite waveguide is shown. The space-time dynamics of spin waves and the characteristics of the band gaps of a magnonic crystal are experimentally studied, and the possibility of controlling the frequency-selective properties of such a structure is shown. By excitation of a superposition of even or odd width modes of the ferrite microstructure, it becomes possible to control the position of the band gaps of a magnonic crystal. The results of the experiment agree with the results of micromagnetic modeling of the propagation and transformation of the spectrum of spin waves propagating in a ferromagnetic periodic structure.

In this work, we study experimentally by broadband ferromagnetic resonance measurements, the dependence of the spin-wave excitation spectra on the magnetic applied field in CoFeB meander-shaped films. Two different orientations of the external magnetic field were explored, namely parallel or perpendicular to the lattice cores. The interpretation of the field dependence of the frequency and spatial profiles of major spin-wave modes were obtained by micromagnetic simulations. We show that the vertical segments lead to the easy-axis type of magnetic anisotropy and support the in-phase and out-of-phase spin-wave precession amplitude in the vertical segments. The latter could potentially be used for the design of tunable metasurfaces or in magnetic memories based on meandering 3D magnetic films.

Studying the spin-wave (SW) propagation in 3D periodic structures opens new possibilities for joining functional units placed on the different layers of the magnonic circuitry. In the path toward 3D magnonics, the main challenge is the fabrication of large-scale 3D magnetic structures with nanometric precision control of geometry and material composition. In this work, we study the dependence on the Ta spacer thickness of the magnonic band structure, measured by Brillouin light scattering spectroscopy, of CoFeB/Ta/NiFe meander-shaped bilayers fabricated on pre-patterned Si substrate with thickness steps of 50 nm. Both propagating and stationary SW modes are observed. While the frequency of the dispersive mode slightly depends on the Ta spacer thickness, the frequency position of the three stationary modes in the lowest frequency range of the spectra significantly increases by increasing the Ta thickness. Micromagnetic calculations indicate that each of the three stationary modes is composed of a doublet of modes whose frequency separation, within each doublet, increases by increasing the mode frequency. The origin of this frequency separation is ascribed to the dynamic dipolar coupling between the magnetic layers that generate a significant frequency nonreciprocity of counterpropagating SWs. For these reasons, the investigated structures offer potential application as the nonreciprocal versatile interconnections performing the frequency selective regimes of signal propagation in magnonic circuits.

Here we present the frequency-selective spin-wave propagation in the magnonic waveguide consisting of two layers with different magnetization saturation. We show that the multimode spin-wave propagation can be performed inside the bilayer structure within two separate frequency range. At the same time this process is accompanied by strong nonreciprocity in spin-wave behavior with the relation to direction of the spin-wave propagation and bias magnetic field. Using the microwave spectroscopy we demonstrate the coexistence of two frequency range in the two samples of pure/modified yttrium iron garnet bilayers with the different orientation of layers with the respect of the substrate. Using the numerical model based on the magnetostatic dispersion relation for spin waves in the bilayer the nonreciprocal behavior of spin-waves was elucidated and its properties for the confined magnonic bilayer stripe was obtained. In particular, it was shown that the narrowing of the stripe leads to the pronounced variation of the nonreciprocity effect for the separate modes in the spin-wave spectra. The experimental data are in good agreement with the predicted by the proposed theoretical model. The proposed concept of bilayer spin-wave waveguide can underlie the fabrication of the magnonic interconnection bus with the support of multiple frequency band operational regimes.

In this article, we report on the Fano resonance characteristics tunability in a coupled system of magnonic stripes and resonators by variating the geometric parameters, the magnitude of the coupling between them, and the intensity of spin waves (SWs). Using numerical integration of the coupled-wave equation system, we calculated the transfer characteristics of the considered system and the parameters of Fano resonance considering the cubic nonlinearity of magnetic media. We demonstrate the features of constructive and destructive interference of SWs at Fano resonance. Our results reveal the mechanism of the SW spectra control of the nonlinear Fano resonance (asymmetry coefficient and resonance frequency shifts) via the intensity of SW.

The features of spin-wave transport in a system of coupled magnetic microwaveguides with perpendicular magnetization relative to the longitudinal axis of the system are considered. In this case, the system has uniaxial anisotropy, the horizontal and vertical coupling coefficients have different signs, and the isofrequency surfaces have a "saddle" shape. In the propagation of transversely limited beams of spin waves, the type of curvature of the wave fronts is determined by the direction of wave propagation relative to the external magnetic field. Keywords: spin waves, magnonics, microwaveguides, lateral structures.

We demonstrate that properties of spin-wave propagation in the adjacent magnonic crystal stripes with one of them in contact with a piezoelectric layer can be controlled by an external electric field. We perform microwave spectroscopy and employ a theoretical approach based on the analysis of the set of coupled wave equations. By considering incident and reflected waves in the first Brillouin zone, we calculate the reflection coefficients of the magnonic structure. Two narrow magnon bands are observed in the experiment, and their behavior with the variation of the electric field applied to the piezoelectric layer was shown. The finite-element calculations of the self-consistent eigenvalue problem elucidate how the influence of the piezoelectric layer can be modeled as a localized strain-induced internal magnetic field and its variation affects the spin-wave dispersion. Both the frequency shift and closing of a magnon band are detected in our measurements and confirmed by the simulations and the analytical approach. Therefore, we demonstrate the electric field control of the magnonic bands. Our results reveal the mechanism of the spin-wave spectra control in the coupled magnonic crystals. The results pave the way for the implementation of frequency selective magnonic devices based on a straintronic approach.

In this work, using numerical and experimental studies, we have demonstrated the possibility of controlling the dipole spin-wave coupling in a lateral array of ferromagnetic stripes using local deformations. As an experimental demonstration of the investigated physical processes, a configuration of a magnonic structure with a piezoelectric layer and structured electrodes on its surface is proposed, and the technique of laser ablation with spatial resolution is used to structure the piezoelectric layer. The mechanisms for controlling the dipole coupling of spin waves by creating elastic deformations localized in the region of the maximums of the electric field are revealed. From an applied point of view, the results obtained can be used to create a class of information processing devices, such as demultiplexing systems with frequency-space selectivity, controlled simultaneously by an electric and magnetic field.

The results of numerical and experimental studies have been used to demonstrate the possibility of controlling the dipole spin-wave coupling in a lateral array of ferrite stripes by means of local deformations. A configuration of a magnonic structure with a piezoelectric layer and structured electrodes on its surface is proposed to use as an experimental demonstration of the studied physical processes, and a laser ablation technique with spatial resolution is used to arrange the piezoelectric layer into a structure. It is shown that local elastic strains can be used to induce a waveguide channel for propagating spin-wave edge modes. From the point of view practical applications, the obtained results can be used to create a class of information processing devices, such as demultiplexing systems with frequency–space selectivity that are controlled simultaneously by an electric and magnetic field.