It is shown that in the transition layer of an epitaxial yttrium iron garnet (YIG) film, there are effects of intense power conversion and redistribution between electromagnetic waves (EMW), exchange spin waves (ESW) and acoustic waves (AW). These interconversion occurs during the cas & scy;ade of double hybridization of EMW-ESW and secondary hybridization of ESW-AW. The necessary phase synchronism condition for this is ensured by the smooth distortion of the ESW dispersion within the thickness direction of the transition layer. The secondary hybridization of ESW-AW manifests itself in the intense excitation of AW, which are radiated into the depth of the gadolinium gallium garnet (GGG) substrate. In this case, magnetoacoustic resonances are excited in the YIG-GGG bilayer structure, for the observation of which strict parallelism and optical polishing of the reflecting surfaces of the YIG-GGG structures are required. An important advantage of magnetoacoustic resonances is the record high quality factor in the microwave range and high resistance to external atmospheric influences, which is of significant interest for the fabrication of highly stable magnetoacoustic microwave generators with discrete frequency tuning.

When an electric current flows through the NiFe/IrMn structure, a significant redistribution of the intensities of the direct Stokes and inverse anti-Stokes lines in spectra of Brillouin scattering on thermal spin waves is observed. This is due to a change in the orientation of uniaxial anisotropy and the corresponding easy axis of the exchange shift under the action of the spin–orbit torque in the IrMn antiferromagnet, which in turn affects the dynamics of spin waves in the neighboring ferromagnetic NiFe layer. The detected effect indicates that spin-wave processes in a ferromagnet can be controlled by applying a spin current to change the magnetic anisotropy of the NiFe/IrMn interface.

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.

Here we study the spin -wave propagation in a system of Mach-Zehnder interferometers (MZI) based on ferrimagnetic yttrium -iron garnet (YIG) thin film. The angular momentum transfer during the excitation of a surface magnetostatic spin wave and the coupling of the spin -waves inside the adjacent arms of MZIs is studied using the micromagnetic modeling method. The local variation of the YIG magnetization inside the arms of MZI manifests itself both in the phase shift of the propagating spin -wave signal and coupling efficiency in the region where the adjacent arms of MZI are placed in the close proximity to each other. The switching/demultiplexing performance which is reflected in the spatial frequency selection of the spin -wave signal upon dynamical local change of the magnetization in each of four arms of the interferometers is demonstrated. The proposed MZI demonstrates the basis for the realization of the set of logical operations and could serve the facility of add and drop frequencies (channels) to and from a magnonic data bus in frequency division multiplexed magnonic networks. The use of laterally coupled interferometers opens new possibilities for the formation of the logical magnon devices tuned by the local variation of magnetization which could be realized with the locally focused laser heating.

Antiferromagnetic (AFM) materials possess a well-recognized potential for ultrafast data processing thanks to their intrinsic ultrafast spin dynamics, absence of stray fields, and large spin transport effects. The very same properties, however, make their manipulation difficult, requiring frequencies in THz range and magnetic fields of tens of Teslas. Switching of AFM order implies going into the nonlinear regime, a largely unexplored territory. Here we use THz light from a free electron laser to drive antiferromagnetic NiO into a highly nonlinear regime and steer it out of nonlinearity with magnetic field from a 33-Tesla Bitter magnet. This demonstration of large-amplitude dynamics represents a crucial step towards ultrafast resonant switching of AFM order.

Using numerical and experimental methods, the mechanism of control of the transmission of a spin-wave signal in a three-dimensional magnon splitter, formed by an orthogonal junction of magnetic strips of yttrium iron garnet, has been investigated. It is shown that by variation the size of the air gap between the spin-waveguide sections, it is possible to control the selection of the signal propagating in the output sections of the structure. From an applied point of view, the results obtained can be used to create an interconnection element in multilevel magnon information processing devices for the formation of multilayer magnon network topologies and miniaturization of computing devices based on the principles of magnonics. Key words: spin waves, magnonics, three-dimensional interconnections, micromagnetic modeling. Keywords: spin waves, magnonic, micromagnetic simulations, three-dimensional structure.

Purpose. Investigation of spin-wave signal passage in a system of magnetic microwaves separated from each other by a one-dimensional array of holes. Using numerical and experimental methods to show controlled spatial-frequency selection of the signal in linear and nonlinear modes of operation. Methods. Micromagnetic modeling of the spatial intensity distributions of spin waves. Obtaining S-parameters of spin waves propagating in a tangentially magnetized structure using a vector circuit analyzer. Results. The spatially selective properties of the structure in linear and nonlinear modes are demonstrated using micromagnetic modeling. A mechanism for controlling the frequency range of the Bragg zone is revealed using a vector analyzer. Conclusion. The proposed structure can be used as a functional element in planar topologies of magnon networks and parallel signal processing devices based on them.

Transition metal oxides are promising for future electronics because of their unique magnetoionic properties and spin-charge interconversion. Here, epitaxial Pd/Co films with an artificially oxidized magnetic layer are studied. The effect of the oxidation dose of the Co layer on the structural and magnetic properties is investigated. The opportunity of epitaxial growth of Pd layers on top of the partially disordered oxide layer with preservation of the epitaxial ratio is shown. The calculations show that the process of oxide formation occurs according to the layer-by-island growth mechanism. An increase in the anisotropy field from the residual thickness of cobalt with an increase in the oxidation dose is observed. The enhancement of the Dzyaloshinskii-Moriya interaction at the interface between the ferromagnet and the oxide layer is experimentally confirmed by analyzing the velocity curves of the asymmetric displacement of domain walls in crossed magnetic fields in the creep mode and is supported by Brillouin light scattering spectroscopy. We demonstrate that the most significant contribution to the interfacial Dzyaloshinskii-Moriya interaction in Pd/Co/CoO films is made by the Co oxide layer. Our findings can be used to develop memory and logic devices of oxide spintronics having advantages of effective control of magnetization state, nonvolatility, low power consumption, and fast data processing.

Here, we present a study investigating the effects of spin-wave coupling in a structure composed of parallel-oriented magnonic stripes fabricated from thin films of yttrium-iron garnet. The structure consists of two parallel stripes separated by a sufficiently small gap to enable dipolar coupling, while a third stripe is positioned atop the lateral system, forming an asymmetric three-dimensional (3D) coupler geometry. Through the utilization of Brillouin light-scattering spectroscopy, we experimentally demonstrate the transport of spin waves along the asymmetric 3D coupler. Additionally, by employing experimental techniques, we explore the nonreciprocal propagation of spin waves in the considered structure by reversing the polarity of the external magnetic field. To gain further insights, we employ micromagnetic modeling and the finite-element method to obtain the eigenmode spectra of the asymmetric 3D coupler. Our results show that reversing the polarity of the external magnetic field induces coupling between the magnetic stripes. We elucidate the characteristics of lateral and vertical spin-wave transport, as well as nonreciprocal spin-wave propagation within the investigated structure. Notably, in the asymmetric 3D coupler, the coupling length diminishes, offering the potential to enhance the density of functional elements in the design of three-dimensional magnonic networks.

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.

In this work, we present the results of investigations performed on hematite (α-Fe2O3), which is an antiferromagnet with weak ferromagnetism. Through the use of Brillouin light scattering spectroscopy, we studied experimentally the excitation of quasi-ferro- and antiferromagnetic modes in the bulk hematite. We investigated the influence of relative mechanical strains, ϵyy, on the frequencies of quasi-ferro- and antiferromagnetic modes. Also, we considered the angular dependence of the frequency of the quasi-ferromagnetic mode on the external magnetic field. Our results indicate that hematite is a suitable material for strain-controlled magnonic devices.

Thin ferromagnet/heavy metal multilayer films are considered as prospective media for a magnetic recording and Co/Pd films are a good example of such materials. In this work, the magnetic properties and micromagnetic structure of Co/Pd multilayer films are studied with different bilayer thicknesses ([Co(0.3 x t nm)/Pd(0.5 x t nm)]10), but with the same ratio Co versus Pd. Transmission electron microscope and X-ray diffraction studies allow authors to suppose that the investigated films are highly mixed alloys. Magnetic force microscopy and Lorentz transmission electron microscopy showed the presence of various micromagnetic features in the films. Along with skyrmions that are well-known magnetic topological artifacts some new features are revealed, which are interpreted as 360 degrees domain walls, skyrmioniums and the combination of the above two. It is found that the type and density of micromagnetic features strongly depend on the bilayer thickness parameter (t). The effect is associated with the peculiarities of interfacial magnetic interactions in the samples with highly mixed interfaces. The tooling coefficient represents a useful tool of the electron beam evaporation technique enabling wide manipulation of micromagnetic particles, in particular, skyrmioniums that are currently considered a prospective media for current driven magnetic recording. The magnetic properties and micromagnetic structure of Co/Pd multilayer films with different bilayer thicknesses, but with the same ratio Co versus Pd are studied. A number of micromagnetic features in the films are revealed, such as skyrmions, 360 degrees domain walls, skyrmioniums and the combination of them. image

Purpose. Investigation of the joint manifestation of the effects of anisotropic signal propagation, coupling, and nonlinear power dependence of the medium parameters in a lattice of laterally and vertically coupled spin-wave (SW) microwaveguides. Consideration of the case of the influence of the rotation of the magnetization angle and the change of the lateral gap between microwaveguides located on the same substrate on the transverse profile of the spin-wave beam and the spatial localization of the SW amplitude. Methods. The method of micromagnetic modeling based on the numerical solution of the Landau–Lifshitz–Hilbert equation shows the possibility of controlling the direction of propagation of SW in an ensemble of laterally and vertically coupled iron yttrium garnet (YIG) microwaveguides by changing the magnetization angle. By the method of numerical integration of the system of coupled discrete nonlinear Schrodinger equations, the possibility of changing the transverse profile of the spin-wave beam by changing the level of the initial signal amplitude is shown. Results. The spatial distributions of the components of the dynamic magnetization of the SW excited in two microwaveguides located on the same substrate obtained in micromagnetic simulations indicate a change in the character of localization of the SW power in the output sections of the microwaveguides. At variation of the lattice magnetization angle, a shift of the threshold power value is observed, at which a characteristic curbing of the transverse width of the spin-wave beam in the nonlinear mode appears. Conclusion. When excitation of surface magnetostatic SW in a lattice of laterally and vertically coupled microwaveguides, a transformation of the transverse profile of the wave is observed at a deviation of the magnetization angle of the structure by 15º , which is manifested in the change of the SW length and its localization in each of the microwaveguides. The combined effects of dipole coupling, gyrotropy, and nonlinearity of the medium make it possible to control the value of the threshold power of the SW, at which the mode of diffractionless propagation of the spin-wave beam is realized in a single layer of the structure.

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.

The motion of domain walls (DWs) in magnetic nanoscale layered systems attracts a great deal of attention due to the possible chiral nature of the energy dissipation occurring because of the presence of strong spin-orbit coupling and the broken inversion symmetry. Here, we report on a giant asymmetry of DWs propagation in the creep regime in the Pd/Co/Pd epitaxial system under the influence of driving out-of-plane (OOP) and symmetry breaking in-plane (IP) magnetic fields. With an increase in the thickness of the bottom Pd layer, which in turn leads to growth of the interface roughness of the Pd/Co/Pd samples, the asymmetry of DWs propagation increases. The maximal reliably measured relation of the velocities of right-handed and left-handed propagating DWs in the Pd(12.5)/Co(0.7)/Pd(3) sample, where thickness is in nanometers, is equal to 6600, which means almost complete blocking of the propagation of DWs in the direction determined by the appropriate choice of a combination of the applied magnetic fields. The observed giant asymmetry of the propagation of DWs indicates the importance of nanoengineering the parameters of the interfaces to control the propagation of DWs in magnetic memory and logic devices.

Here we present the results of the study of the joint manifestation of the effects of anisotropic spin waves (SW) propagation in a system of laterally and vertically coupled ferrimagnetic microwaveguides when both the magnetization angle and air gap between waveguide are changed. The micromagnetic modeling method based on the numerical solution of the Landau–Lifshitz–Hilbert equation was used to provide the possibility of controlling the direction of SW propagation in a system of laterally and vertically coupled iron-yttrium garnet (YIG) microwaveguides by changing the magnetization angle and direction of the equilibrium of magnetization direction. The spatial distributions of the dynamic magnetization out-of-plane component of the SW excited in two microwaveguides located on the same substrate obtained in micromagnetic simulations indicate a change in the nature of the SW power localization in the output sections of the microwaveguides. The variation of the magnetization angle of the array leads to the variation of the transverse width of the spin-wave beam and localization of the amplitude maximum in each of the microwaveguides within the array. The joint manifestation of dipole coupling effects in each separately taken layer of the structure realizes the regime of non-diffraction propagation of the spin-wave beam.

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.