In this work, we present the results of a systematic experimental study of linear and parametric spin wave resonant excitation accompanied by spin currents (spin pumping) in a multifrequency composite bulk acoustic wave resonator with a ZnO-YIG-GGG-YIG/Pt structure. The features of magnetic dynamics excitation in YIG films due to magnetoelastic coupling with acoustic thickness modes of various polarizations are studied. Acoustic spin waves and spin pumping are detected by simultaneous frequency-field mapping of the inverse spin Hall effect voltage and the resonant frequencies of thickness extensional modes. In the parametric range of frequencies and fields, acoustic spin pumping induced by both shear and longitudinal polarization modes was observed. Linear acoustic spin waves are excited only by shear thickness extensional modes because longitudinal acoustic waves do not couple with the magnetic subsystem in linear regime.

Acoustic resonance spectroscopy (ARS) is an informative analytical method that yields information about thicknesses and acoustic properties of layers in a multilayer structure representing a high-overtone bulk acoustic wave resonator (HBAR). Since the HBAR spectrum has many resonance features, the development of automatic methods for its processing is an urgent task. In this study, a method for extracting ARS data from a signal distorted by a RF measuring path without additional measurements of reference impedances (calibration) is proposed, which brings the spectrum to a form convenient for automatic processing and significantly expands the range of the ARS application. The method is especially relevant for processing HBAR spectra with a low excitation efficiency. As an example of such processing, the central frequencies and effective widths of more than a thousand resonant peaks are determined and, based on this, the frequency dependence of the acoustic attenuation is established for a new material: optical ceramics based on doped yttrium aluminum garnet nanoparticles.

Acoustic resonance spectroscopy (ARS) is an informative analytical method that yields information about thicknesses and acoustic properties of layers in a multilayer structure representing a high-overtone bulk acoustic wave resonator (HBAR). Since the HBAR spectrum has many resonance features, the development of automatic methods for its processing is an urgent task. In this study, a method for extracting ARS data from a signal distorted by a RF measuring path without additional measurements of reference impedances (calibration) is proposed, which brings the spectrum to a form convenient for automatic processing and significantly expands the range of the ARS application. The method is especially relevant for processing HBAR spectra with a low excitation efficiency. As an example of such processing, the central frequencies and effective widths of more than a thousand resonant peaks are determined and, based on this, the frequency dependence of the acoustic attenuation is established for a new material: optical ceramics based on doped yttrium aluminum garnet nanoparticles.

The 1D model of an acoustic resonator structure with a ferromagnetic layer on a nonmagnetic substrate and piezoelectric thin-film piezoelectric transducer is considered. The double resonance conditions, i.e., the magnetoelastic resonance in a magnetic layer and purely elastic resonance in the whole multilayer structure are investigated. The acoustic generation of spin waves in these conditions is characterized by the behavior of the electric impedance of a transducer in the magnetic field. The analytical expression for the impedance is obtained. This expression is derived taking into account the disorientation of the transducer polarization and magnetic field. The numerical calculations show that even the weak disorientation 5° causes the manifestation of the acoustic birefringence phenomenon.

The conditions for the parametric instability of magnons under the action of purely elastic pumping, which are modes of a composite acoustic wave resonator containing ferrimagnet and piezoelectric films on a single-crystal substrate, are considered. Electrical excitation of bulk acoustic waves occurs due to the piezoelectric effect (in a ZnO film) at resonant frequencies fn of the resonator. In a magnetically ordered layer (in a film of yttrium iron garnet), acoustic modes, when the threshold power is exceeded, excite magnons at frequencies fn/2. It is shown that, in the case of pumping by transverse acoustic modes, the threshold is several tens of times smaller than in the case of pumping by longitudinal modes and is approximately 100 μW, which is in agreement with experimental data.

Using broadband acoustic resonator spectroscopy, an almost twofold increase in the frequency of optimal excitation of the composite microwave resonator of shear bulk acoustic waves is found when the distance from the substrate to the magnetron axis during the deposition of a ZnO film by magnetron sputtering is changed. The frequency characteristics of the resonator structure are simulated and an explanation of the change in the optimal excitation frequency by the inhomogeneity of the inclination of the ZnO film texture’s axis over the thickness is proposed.

We report on the experimental observation of excitation and detection of parametric spin waves and spin currents in the bulk acoustic wave resonator. The hybrid resonator consists of a ZnO piezoelectric film, yttrium iron garnet (YIG) films on a gallium gadolinium garnet substrate, and a heavy metal Pt layer. Shear bulk acoustic waves are electrically excited in the ZnO layer due to piezoeffect at the resonant frequencies of the resonator. The magnetoelastic interaction in the YIG film emerges magnons (spin waves) excitation by acoustic waves either on resonator's eigenfrequencies or the half-value frequencies at supercritical power. We investigate the acoustic pumping of magnons at the half-value frequencies and acoustic spin pumping from parametric magnons, using the inverse spin Hall effect in the Pt layer. The constant electric voltage in the Pt layer, depending on the frequency, the magnetic field, and the pump power, was systematically studied. We explain the low threshold obtained (∼0.4 mW) by the high efficiency of electric power transmission into the acoustic wave in the resonator.

The features of phonon–magnon interconversion in acoustic resonator determine the efficiency of spin pumping from YIG into Pt that may be detected electrically through the inverse spin Hall effect (ISHE). Based on the methods developed in previous works for calculating resonator structures with a piezoelectric (ZnO) and a magnetoelastic layer in contact with the heavy metal (YIG/Pt), we present the results of numerical calculations of YIG film thickness influence on acoustically driven spin waves. We obtain some YIG film thickness regions with various behavior of dc ISHE voltage UISHE. At micron and submicron thicknesses, the higher spin wave resonance (SWR) modes (both even and odd) can be generated with efficiency comparable and even exceeding that of the main mode. The absolute maximum of UISHE is achieved at the thickness about s1 ≈ 208 nm under the excitation of the first SWR.

A theory of acoustic spin pumping in a bulk acoustic wave resonator with a ZnO-YIG-GGG-YIG/Pt structure is presented, with allowance for the exchange contribution to the formation of a coupled magnetoelastic wave spectrum, and the back action of acoustically excited magnetic dynamics in YIG films on the elastic subsystem in all layers. Good agreement is achieved between the theoretical and experimental frequency–field dependences of the resonant frequencies of the resonator and the voltage magnitude of the inverse spin Hall effect in Pt.

We report on the self-consisted semi-analytical theory of magnetoelastic excitation and electrical detection of spin waves and spin currents in hypersonic bulk acoustic waves resonator with ZnO-GGG-YIG/Pt layered structure. Electrical detection of acoustically driven spin waves occurs due to spin pumping from YIG to Pt and inverse spin Hall (ISHE) effect in Pt as well as due to electrical response of ZnO piezotransducer. The frequency-field dependences of the resonator frequencies and ISHE voltage U-ISHE are correlated with experimental ones observed previously. Their fitting allows to determine some magnetic and magnetoelastic parameters of YIG. The analysis of the YIG film thickness influence on U-ISHE gives the possibility to find the optimal thickness for maximal U-ISHE value.

We report on the first observation of microvolt-scale inverse spin Hall effect (ISHE) dc voltage driven by an acoustic spin pumping (ASP) in a bulk acoustic wave (BAW) resonator formed by a Al-ZnO-Al-YIG(1)-GGG-YIG(2)-Pt structure. When 2 mW power is applied to an Al-ZnO-Al transducer, the voltage VISHE ∼ 4 μV in the Pt film is observed as a result of resonant ASP from YIG(2) to Pt in the area ∼ 170 μm. The results of frequency and magnetic field mapping of VISHE(f,H) together with reflectivity of the resonator show an obvious agreement between the positions of the voltage maxima and BAW resonance frequencies fn(H) on the (f, H) plane. At the same time a significant asymmetry of the VISHE(fn(H)) value in reference to the magnetoelastic resonance (MER) line fMER(H) position is revealed, which is explained by asymmetry of the magnetoelastic waves dispersion law.

Abstract—In this paper, we present theoretical and experimental results on the excitation and detection of spin waves and spin currents in multifrequency bulk acoustic wave resonators containing iron–yttrium garnet (YIG) films in contact with the Pt film. Acoustically excited magnetic precession under the resonator conditions was established to produce spin pumping that also has a resonance character. A significant asymmetry in the frequency dependence of the voltage signal detected on the Pt film is revealed with respect to the frequency of the magnetoelastic resonance and is confirmed by theoretical calculations. Acoustic resonator spectroscopy in combination with the electric detection of magnetic dynamics using the inverse spin Hall effect is shown to be of interest for studying the dispersion of spin waves, as well as magnetic and magnetoelastic parameters of ferromagnetic films.

The optimization of technological parameters for fabrication of the inclined texture [0001] in ZnO films has been conducted. It is shown that the inclination of the texture axis is determined by at least two factors: the average vector of falling the deposited particles and the intensity of bombardment of the growing film with negative ions of oxygen. Optimum displacements of the substrate position relative to the axis of the sputtering system and the distance between the planes of the target and the substrate are determined. Films of zinc oxide with optimum angles of inclination of texture axis have been obtained by the RF sputtering technique.

A new way of generating a pure spin current using a magnetoelectric composite high-overtone bulk acoustic-wave resonator (HBAR) based on a layered Al–ZnO–Al–Gd 3 Ga 5 O 12 –Y 3 Fe 5 O 12 –Pt structure is proposed. It is established that the efficiency of generating the rf magnetic field driving the spin current by this method exceeds that of sources which use surface acoustic waves for the excitation of magnetic dynamics and is not inferior to the efficiency of usual electromagnetic ways of exciting a pure spin current that employ microwave cavities.

High overtone bulk acoustic wave resonator with (Al-ZnO-Al)/GGG/YIG/Pt structure was theoretically considered, fabricated and experimentally examined for acoustic spin pumping — acoustically driven generation of pure spin current at YIG/Pt interface.

Акустическая спиновая накачка – генерация чистого спинового тока, порождаемого магнитной динамикой, возбуждаемой акустической волной – в настоящее время привлекает к себе пристальное внимание в связи с возможным её использованием для решения задач спинтроники - отдела современной электроники, исследующего возможность передачи и хранения информации с помощью спина, а не заряда электрона. В докладе мы сообщаем о генерации чистого спинового тока при возбуждении магнито-упругого резонанса (МУР) в микроминиатюрном магнитоэлектрическом составном многомодовом резонаторе на объёмных акустических волнах (ОАВ), образованном слоистой структурой Al-ZnO-Al-ГГГ-ЖИГ. Прецессия намагниченности в эпитаксиальном ЖИГ возбуждается и детектируется непосредственно при помощи электроакустического преобразователя (Al-ZnO-Al), а возбуждаемая акустическим образом в плёнке ЖИГ магнитная динамика используется для накачки спинового тока в слой платины, напылённой на поверхность магнитной плёнки. Для детектирования спинового тока мы используем метод, основанный на регистрации напряжения, обусловленного обратным спиновым эффектом Холла. Этот эффект состоит в появлении разности потенциалов на границах плёнки материала с высокой спин-орбитальной связью (в нашем случае - платины), вызванной поглощением в ней спинового тока. Величина такого напряжения напрямую зависит от силы спинового тока, что позволяет провести сравнение эффективности накачки предлагаемым нами акустическим методом как с традиционными методами, использующими для возбуждения магнитной динамики объёмные микроволновые резонаторы [1] и полосковые линии [2], так и с акустическим методом генерации спинового тока, использующим поверхностные акустические волны [3].

Non-magnetic ways of exciting magnetic oscillations, in particular due to strain mediated coupling between the electric field in a piezoelectric film and magnetization in a magnetostrictive ferromagnetic layer, are quite topical today because of possible applications in strain-tunable spintronic devices, magnetoelectric spin wave logic circuits, and sensors. Acoustic spin pumping (ASP), the generation of spin currents from a magnetization precession excited by a microwave phonons, has attracted much attention recently. The possibility for pure spin current generation based on acoustic driving magnetic dynamics both under magnetoelastic resonance (MER) [1] and the off-resonance conditions [2] has been demonstrated. In [3, 4] we showed theoretically and observed experimentally that excitation of non-uniform ferromagnetic resonance (FMR) occurs in a Al-ZnO-Al-GGG-YIG high overtone bulk acoustic wave resonator (HBAR) at frequencies close to the ones of MER. Magnetic oscillations in YIG arise because of spatially inhomogeneous strain and manifest themselves as HBAR resonance frequency shift Δf_n(H) at magnetic fields H corresponding to MER, when HBAR resonance frequency f_n(H) is close to FMR frequency. The generation of pure spin current in such HBAR has been demonstrated recently in [5]. Magnetic dynamics excited acoustically in the YIG film induces spin current from it into a thin layer of platinum deposited on the YIG. This spin-polarized current is transformed to electrical current by means of the inverse spin Hall effect (ISHE). Here, we report some important features of generation of pure spin current in such a system caused by crystal and magnetoelastic anisotropy. Namely, the effect of the mutual orientation of the transverse acoustic wave polarization (established by the projection of ZnO texture axis on a plane (111) of epitaxial YIG films), the bias magnetic field and the platinum strip on the maximal value of HBAR frequency shift (Δf_n) and ISHE voltage (U_ISHE) has been studied in detail. We found that, in contrast to the standard sinusoidal dependence of U_ISHE versus angle ϕ between the magnetizing field and Pt strip observed at electromagnetic excitation by cavities or striplines, the angular dependence of U_ISHE(ϕ) at ASP in HBAR is subject to more complex law. This is because only transverse acoustic waves with the components of particle displacement parallel to the bias field are able to excite magnetic oscillations. A model is proposed to explain the observed behavior of U_ISHE(ϕ) and Δf_n (ϕ). Fitting the experimental curves with the obtained theoretical dependences allowed us to determine the location of projection of ZnO texture axis in the plane (111) of YIG. The locations extracted from U_ISHE(ϕ) and Δf_n(ϕ) measurements are in good agreement with each other. It is concluded that in order to obtain the maximal value of U_ISHE, the piezoelectric texture axis of ZnO should be oriented towards the direction that is perpendicular to the axis of the platinum strip and parallel to the crystallographic axis of YIG film.