Background and Objectives: Thin-film structures of yttrium iron garnet ferrite film – platinum are actively studied due to the possibility of using the direct (for converting electric current in platinum into spin waves in ferrite) and inverse (injection of spin current from ferrite into platinum film) spin Hall effects for application in magnonics and spintronics devices. Materials and Methods: The structures studied in this work were obtained on the basis of yttrium iron garnet films of crystallographic orientations (100) and (111), from which waveguides were cut out, in which spin waves were excited. Their propagation was monitored using a vector network analyzer. A platinum film in the form of stripe oriented along the long axis of the waveguide was fabricated on the surface of the waveguides using magnetron sputtering, photolithography, and ion etching. Spin injection from ferrite film in the platinum film results in electric charge current generation. An experimentally measured value was the electromotive force between contacts to the platinum stripe. It was measured using a synchronous detector. The measurements were carried out at magnetization field values lower than the saturation field of the ferrite film, with the magnetic structure of the film being divided into domains. Results and Conclusions: It has been shown that for both crystallographic orientations the maximum spin injection is achieved when magnetizing the waveguides along the easy magnetization axis and symmetrical domain structure is formed.

The purpose of this work is to experimentally study, using the inverse spin Hall effect (ISHE), the detection of focused beams of magnetostatic surface waves (MSSW) in integrated YIG (3.9 µm) / Pt (4 nm) thin-film microstructures, where the focusing effect was ensured by the curvilinear shape of the exciting antenna. Make a comparison with the case of detecting MSSWs excited by a rectilinear antenna. Methods. Experiments were carried out using the delay line structures based on the YIG/Pt. The amplitude-frequency characteristics of the YIG/Pt structure and the frequency dependence of the EMF (V(f)) induced in platinum were studied. Results. It was shown that at frequencies f near the long-wavelength limit of the MSSW spectrum, the magnitude of the EMF V(f) generated by a focused MSSW can be several times higher than the values of V(f) in the case of MSSW excitation by a common (straight) antenna. In this case, in the short-wavelength part of the spectrum, on the contrary, the magnitude of the EMF generated by the focused MSSW beam turns out to be noticeably smaller. This behavior is associated with chromatic aberration of the focusing antenna for the MSSW, which manifests itself in the frequency dependence of the focal length of the antenna, which is confirmed by the results of micromagnetic modeling. It is shown that the drop in the EMF signal generated by a focused MSSW beam in the short-wavelength part of the spectrum is associated with the focus reaching the area of the YIG not covered with the Pt film. In this case, the increase in V(f) in the long-wavelength region of the MSSW spectrum is explained by an increase in the linear power density of the MSSW and the formation of caustics under the Pt film. Conclusion. Obtained results can be used for the development of highly sensitive spin wave detectors and the creation of spin logic devices.

The spin pumping by traveling magnetostatic surface waves (MSSW) in two YIG/Pt structures corresponding to the cases of MSSWpropagation along the [100] direction (hard axis of magnetization) and [110] direction(easy axis of magnetization) has been studied using the inverse spin Hall effect (ISHE). It is shown that the cubic anisotropy field does not change the character of the frequency dependences of the electromotive force U ISHE (f), but for the [110] direction it leads to an increase in the signal U ISHE (f) and an upward shift in frequency by 410 MHz relative to the case of magnetization along the «hard» axis.

Spin pumping by surface and backward volume magnetostatic waves in YIG/Pt structures is experimentally studied and analyzed. It is shown that at frequencies corresponding to van Hove singularities in the density of states of the spin wave spectrum, an increase in the efficiency of electron-magnon scattering and spin current generation takes place. The obtained results are important for spin wave-based spintronic devices development.

In a structure of an epitaxial film of yttrium iron garnet (YIG) with crystallographic orientation (111) 11.8 μm thick and a 5 nm thick platinum (Pt) film deposited on its surface, the effect of EMF generation in a platinum film during the propagation of magnetostatic waves (MSW) in the structure was studied at values of the tangential constant magnetic field H less than the saturation field H_s~65 Oe of the YIG film. The experiments were performed in a geometry where the field H was parallel to the crystallographic direction [1¯21] and to the MSW antennas, and the distances from the input antenna to the output antenna and to the Pt film were ~5 mm and ~0.5 mm, respectively. In the structure under consideration, at |H|<H_s, a stripe domain structure (SDS) was formed, which in fields |H|<H_1~5 – 7 Oe acquired a branching character in the near-surface layer. In the range of fields H_1<|H|<H_2≈40 Oe, MSW propagation was observed in the frequency band ∆F_1~ 300-550 MHz, which was accompanied by EMF generation due to the inverse spin Hall effect. In the interval H_2<|H|≤H_s, MSW propagation was observed in the frequency band ∆F_2≈ 750-1750 MHz, while the frequency interval in which the EMF signal was recorded turned out to be several times smaller due to the development of MSW parametric instability.

Background and Objectives: Layered structures based on ferrite and metal films are actively studied in magnonics. Usually, the effects associated with the finite conductivity of the metal are not taken into account. The aim of this work was to investigate the influence of the thickness of a metal with finite conductivity on the dispersion and damping of a magnetostatic backward volume wave (MSBVW) in the ferrite-metal and ferrite-insulator-metal structures. Materials and Methods: The dispersion equation for MSBVW was derived using Maxwell’s equations in the magnetostatic approximation, the Landau-Lifshitz equation, and standard electrodynamic boundary conditions. Calculations were performed for the structures based on yttrium iron garnet (YIG) films with metal resistivity characteristic of silver, indium, and copper. Results of the calculation we compared with results of an experiment on MSBVW propagation in a YIG film metallized by copper performed using a vector network analyzer and microstrip antennas for excitation and detection of the MSBVW. Results and Conclusions: It was found that, the metallization always suppresses MSBVW propagation, and at metal thicknesses t ≥ 10 nm, the ohmic losses due to the metal significantly exceed the intrinsic magnetic losses in the ferrite. It was also shown that the gap between the ferrite and metal can be used to suppress the long-wavelength part of the MSBVW spectrum.

Using the inverse spin Hall effect (ISHE), spin pumping by traveling surface waves (MSSW) and backward volume waves (BVMSW) in YIG/Pt microstructures has been experimentally studied. It has been discovered that the frequency dependence of the emf UISHE(f), generated due to the ISHE, in the case of BVMSW is characterized by a maximum near the frequency of the long-wave (f0) spectrum boundary. In the case of a MSSW, the dependence UISHE (f) exhibits maxima both at the frequency f0 and at the frequency fs of the short-wave boundary of the MSSW spectrum. The indicated differences in the dependences UISHE (f) for MSSW and OOMSW are explained by the difference in the functions of the density of states of spin waves in the spectrum of MSSW and BVMSW.

The purpose of this work is to study the influence of four-magnon (4M) parametric instability on spin pumping by dipole-exchange magnetostatic surface waves (MSSW) with the help of the inverse spin Hall effect (ISHE) in structures based on yttrium-iron garnet (YIG) and platinum (Pt). Methods. The experiments were carried out using the delay line structures based on YIG(900 nm)/Pt(9 nm) where electromotive force (EMF) induced by ISHE demonstrates a growth at the frequencies of the resonant interaction between MSSW and volume exchange modes. The frequency dependencies of the amplitude and phase for the delay line structure and EMF (𝑈(𝑓)) from the platinum layer were studied as a function of the MSSW power. Results. It was shown that the resonant EMF growth at the frequencies of dipole-exchange resonances is caused by the presence of Van Hove singularities in the density of states for spin waves at such frequencies that leads to an increase in the efficiency of electron-magnon scattering at the YIG–Pt interface. A growth in MSSW power beyond the threshold of 4M instability development results in a “smoothing” of resonant particularities in the EMF frequency dependence 𝑈(𝑓) that can be explained by decreasing efficiency of spin pumping due to destruction of dipole-exchange resonances and related singularities in the density of states of spin waves. Conclusion. Obtained results may be of interest for the development of highly sensitive spin current detectors, as well as for the implementation of spintronic devices.

Multielectrode microantennas for spin waves integrated with a ferrite waveguide – yttrium iron garnet film – were fabricated and tested. Microantennas of two types were studied: with a parallel connection of conductors – “grating” and with a serial connection of conductors – “meander”. The performance of such microantennas for excitation of magnetostatic surface and backward volumec waves tens of micrometers in length has been demonstrated. It has been shown that for waves with a length of tens of micrometers, high (tens of megahertz) excitation selectivity can be achieved using the “grating” microantennas. Whereas, using the “meander” microantennas for the same wavelength range, it is possible not only to get selectivity, but also to significantly (up to 10 dB) increase the excitation efficiency compared to the microantenna with a single conductor. It is noted that the use of such microantennas for shorter spin waves can be hampered by the mutual influence of microwave fields from neighboring conductors, as well as the increasing role of ohmic losses in conductors.

The effect of EMF generation due to the inverse spin-Hall effect during the propagation of magnetostatic surface waves (MSSW) in the structure of yttrium iron garnet (YIG) --- platinum based on a two-layer YIG film with different saturation magnetizations of the layers ((4π M 1 >4π M 2 ) has been experimentally studied. It was shown that the magnitude of the EMF resonantly increases at the frequencies of hybridization of the MSSW with the exchange modes of the structure. At the same time, at the frequencies of the MSSW of the layer with a higher magnetization, oscillations of the EMF are observed, caused by its hybridization with the exchange modes of both the layer with 4π M 1 and the layer with lower magnetization, which indicates the influence of interlayer exchange on the efficiency of spin pumping in the structure under consideration. The influence of the interference of counterpropagating MSSWs on the generated EMF has been studied. It has been shown that the EMF value is sensitive to the phase difference between counterpropagating MSSWs and oscillates. In this case, the amplitude of the oscillations is determined by the ratio of the wavelength of the MSSW and the length of the platinum film. Keywords: magnetostatic waves, yttrium iron garnet, platinum, interference, inverse spin Hall effect.

Both inverse spin Hall effect (“interface”) and electron drag by magnons (“bulk”) mechanisms of the electromotive force generation by travelling magnetostatic surface (MSSW) and backward volume (MSBVW) waves in YIG/Pt and YIG/n-InSb microstructures are studied. It is shown that “interface mechanism” plays the main role in YIG/ Pt bilayers, while for YIG/n-InSb structures, electron drag by magnons dominates. Giant oscillations of the voltage caused by inverse spin Hall effect were observed in YIG/Pt structures at frequencies corresponding to resonance interactions of MSSW with the volume exchange modes.

Using micromagnetic simulations, we show the possibility to build spin logic devices based on films of yttrium iron garnet and permalloy where energy channeling of spin waves is achieved due to excitation of focused and narrow-directed wave beams with used antennas. We studied the methods to construct a majority logic gate based on the interference of caustics of spin waves excited with the rectilinear transducers directed at an angle to the in-plane magnetic field. We propose the approach that allows using of amplitude detector to build a truth table and that consists in adding a reference signal with the fixed initial phase to three information signals. The possibility to scale the device on the example of its work in the range of spin waves with micron and submicron wavelengths is demonstrated.

With the help of micromagnetic modeling, we considered particularities of dispersions and amplitude-frequency response of spin waves in a magnonic crystal (MC) formed by etching an array of grooves in the surface of yttrium iron garnet film having linear distribution of magnetization across the thickness from 1.7 kG at the upper surface till 2.02 kG at the bottom. For the geometry of surface magnetostatic spin waves (MSSW), it is shown that nonuniformity of magnetization distribution across the thickness leads to the appearance of frequency regions in the MC spectrum where MSSW propagation is unidirectional and, as the consequence, does not have Bragg resonances. It was also demonstrated that the MC spectrum is determined by the choice of surface used for the formation of the array of grooves. Keywords: spin wave, micromagnetic modelling, film of yttrium iron garnet, magnonic crystal.

With the help of micromagnetic modeling, we considered particularities of dispersions and amplitude-frequency response of spin waves in a magnonic crystal (MC) formed by etching an array of grooves in the surface of yttrium iron garnet film having linear distribution of magnetization across the thickness from 1.7 kG at the upper surface till 2.02 kG at the bottom. For the geometry of surface magnetostatic spin waves (MSSW), it is shown that nonuniformity of magnetization distribution across the thickness leads to the appearance of frequency regions in the MC spectrum where MSSW propagation is unidirectional and, as the consequence, does not have Bragg resonances. It was also demonstrated that the MC spectrum is determined by the choice of surface used for the formation of the array of grooves.

The effect of EMF generation due to the inverse spin-Hall effect during the propagation of surface magnetostatic waves (SMSW) in the structure of yttrium iron garnet (YIG) - platinum based on a two-layer YIG film with different saturation magnetizations of the layers ((4πM_1>4πM_2 ) has been experimentally studied. It was shown that the magnitude of the EMF resonantly increases at the frequencies of hybridization of the MSSW with the exchange modes of the structure. At the same time, at the frequencies of the MSSW of the layer with a higher magnetization, oscillations of the EMF are observed, caused by its hybridization with the exchange modes of both the layer with 4πM_1 and the layer with lower magnetization, which indicates the influence of interlayer exchange on the efficiency of spin pumping in the structure under consideration.The influence of the interference of counterpropagating MSSWs on the generated EMF has been studied.It has been shown that the EMF value is sensitive to the phase difference between counterpropagating MSSWs and oscillates.In this case, the amplitude of the oscillations is determined by the ratio of the wavelength of the MSSW and the length of the platinum film.

In this work, the particularities of the spin wave (SW) excitations in corrugated yttrium-iron garnet (YIG) films with a thickness of 0.2 mu m and a corrugation period of 20 mu m were studied by micromagnetic simulations. Strong influence of the corrugation depth, changing from 0 to 0.5 mu m, on SW dispersion, transmission and eigenmode spectrum was shown. Formation of a bandgap resulting from the spin-wave resonances in the sidewalls of the corrugated YIG film was discovered in the SW dispersion and transmission spectrum in addition to the Bragg bandgaps and dipole-exchange resonance.

In this work, we present experimental data on the interference of backward volume magnetostatic wave (BVMSW) counter-propagating in the structure with two exchange-coupled yttrium iron garnet layers. The layers are engineered to have different saturation magnetization that gives a possibility to BVMSW resonantly interacting with exchange modes of the two-layer structure. The BVMSW is excited by two antennas placed on top of the structure, while the third one placed between them is used for the detection of inductive voltage V generated by waves superposition. It is shown that maximal changes of the output inductive signal δV with the variation of magnetic field δH occur if, first, the waves interfere destructively and, second, the frequency corresponds to the resonant interaction of BVMSW with the exchange waves. In this case, obtained data reveal large sensitivity S = δV/δH approaching S ≈ 267 dB/Oe in the vicinity ±0.1 Oe of the resonant field H. The observed high sensitivity is of great importance for the development of compact sensitive magnetometers operating at room temperature.

The purpose of this work is to find out the influence of three-magnon decay processes on the electromotive force (EMF (U)) generated by propagating magnetostatic surface waves (MSSW) with the help of the inverse spin Hall effect in the “yttrium-iron garnet (YIG) – platinum (Pt)” structure. Methods. The experiments were carried out using the delay line structures based on YIG films with the thickness of 8.8 and 14.6 µm, on the surface of which antennas were formed for MSSWs excitation and reception and a Pt film between antennas. Results. It was shown that the three-magnon parametric instability can significantly change the character of EMF dependences on frequency and on power of MSSW that resulted both from the effect of power limitation and from the participation of parametric spin waves (PSW) and secondary spin waves (SSW) in the processes of electron-magnon scattering on the YIG/Pt border. Conclusion. It was demonstrated that the effect of amplification of EMF generation at the frequencies that are close to the long-wavelength border of the MSSW spectrum is related with the PSW and SSW population of the region of anisotropic dipole-exchange spin waves spectrum, which is characterized by the presence of singularities in the magnon density of states (Van Hove singularities).

The spectrum of spin waves (SW) of tangentially magnetized films of yttrium iron garnet (YIG) with a surface metastructure in the form of gratings of etched grooves with a period Λ close to the film thickness d (Λ~d) has been experimentally and numerically studied. It has been found that the spectrum of the signal reflected from a microstrip transducer with a width w>>d,Λ located on the YIG film contains absorption lines associated with the excitation of the SW of the surface metastructure. In the case when the magnetic field H and the transducer are oriented along the grooves, the absorption lines of the metastructure are located at frequencies f* near the short-wavelength edge of the spectrum of the surface magnetostatic (Damon-Eshbach) wave fs. It is shown that f* linearly depends on H , which can be used to develop magnetic field sensors. The results of measurements of dependences f* (H) are in qualitative agreement with the results of micromagnetic modeling.

The spectrum of spin waves (SW) of tangentially magnetized films of yttrium iron garnet (YIG) with a surface metastructure in the form of gratings of etched grooves with a period close to the film thickness d (~ d) has been experimentally and numerically studied. It has been found that the spectrum of the signal reflected from a microstrip transducer with a width w>> d, located on the YIG film contains absorption lines associated with the excitation of the SW of the surface metastructure. In the case when the magnetic field H and the transducer are oriented along the grooves, the absorption lines of the metastructure are located at frequencies f * near the short-wavelength edge of the spectrum of the surface magnetostatic (Damon--Eshbach) wave f s . It is shown that f * linearly depends on H, which can be used to develop magnetic field sensors. The results of measurements of dependences f * (H) are in qualitative agreement with the results of micromagnetic modeling. Keywords: magnetostatic waves, one-dimensional grating, surface structure, sensor of magnetic field.