Magnetoacoustic Resonance Research Articles

Theory of Magnetoacoustic Resonance to Probe Multipole Effects Due to a Crystal Field Quartet

Theory of Magnetoacoustic Resonance to Probe Multipole Effects Due to a Crystal Field Quartet

THz and sub-THz antiferromagnetic magnons via magnetoacoustic resonances excited by picosecond strain pulses in NiO

THz and sub-THz antiferromagnetic magnons via magnetoacoustic resonances excited by picosecond strain pulses in NiO

Nonreciprocal transmission of magnetoacoustic waves in compensated synthetic antiferromagnets

We investigate the interaction between surface acoustic waves (SAWs) and spin waves (SWs) in a Pt/Co($2\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$)/Ru($0.85\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$)/Co($2\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$)/Pt compensated synthetic antiferromagnet (SAF) composed of two ferromagnetic layers with equal thicknesses separated by a thin nonmagnetic Ru spacer layer. Because of the combined presence of interlayer dipolar coupling fields and interfacial Dzyaloshinskii--Moriya interaction (iDMI), the optical SW mode shows a large nondegenerate dispersion relation for counter-propagating SWs. Due to resonant SAW-SW interaction, we observe a nonreciprocal SAW transmission in the prepared piezoelectric/SAF hybrid device. We demonstrate that the nonreciprocity of the SAW transmission in symmetric SAFs with equal thicknesses of the magnetic layers can show a substantially different characteristic behavior in comparison to asymmetric SAFs or magnetic single layers with iDMI. For the prepared SAF, the nonreciprocal shift of the magnetoacoustic resonance fields and the magnetoacoustic SW excitation efficiency depend on the external magnetic field sweep direction. For one magnetic field sweep direction and angle of the magnetic field, the resonance fields of the waves propagating in one direction are larger than for the waves propagating in the opposite direction. In addition, the magnitude of the nonreciprocal field shift is at minimum if the external magnetic field is aligned perpendicular to the SW propagation direction. The experimental results are in agreement with a phenomenological SAW-SW interaction model.

Electrically excited magnetoelastic waves and magnetoacoustic resonance in ferromagnetic films with voltage-controlled magnetic anisotropy

Ferromagnet-dielectric heterostructures may possess interfacial magnetic anisotropy, which varies with the electric field created in the dielectric interlayer. Such a voltage-controlled magnetic anisotropy (VCMA) represents an efficient tool for the excitation of spin waves without the use of microwave magnetic fields. In ferromagnets with a significant magnetoelastic coupling between spins and strains, however, the magnetization precession in the spin wave induces elastic vibrations. Here we report micromagnetoelastic simulations of the coupled spin and acoustic dynamics generated in the thick Fe film brought into contact with an MgO nanolayer subjected to a microwave voltage. It is found that the electrically induced periodic modulation of VCMA gives rise to the excitation of both spin and elastic waves in the magnetostrictive Fe film. Remarkably, the magnetoelastic coupling makes it possible to generate propagating spin waves having frequencies well below the ferromagnetic resonance frequency. Furthermore, when the voltage frequency approaches a value ${\ensuremath{\nu}}^{*}$ at which the dispersion relations of pure spin and transverse elastic waves cross, the excitation of traveling magnetoelastic waves with a specific hybrid dispersion occurs in the Fe film. To explain the variety of observed phenomena, we propose a generalized dispersion relation for magnetoelastic waves, which accounts for a possible difference between the wave numbers of their magnetic and elastic components. The analysis of the simulation data also reveals that frequency dependencies of the amplitudes of magnetic oscillations and elastic vibrations display significant anomalies around the crossing-point frequency ${\ensuremath{\nu}}^{*}$, which originate from the electrically induced magnetoacoustic resonance.

All-Optical Generation and Time-Resolved Polarimetry of Magnetoacoustic Resonances via Transient Grating Spectroscopy

The generation and control of surface acoustic waves (SAWs) in a magnetic material are objects of an intense research effort focused on magnetoelastic properties, with fruitful ramifications in spin-wave-based quantum logic and magnonics. We implement a transient grating setup to optically generate SAWs also seeding coherent spin waves via magnetoelastic coupling in ferromagnetic media. In this work we report on SAW-driven ferromagnetic resonance (FMR) experiments performed on polycrystalline Ni thin films in combination with time-resolved Faraday polarimetry, which allows extraction of the value of the effective magnetization and of the Gilbert damping. The results are in full agreement with measurements on the very same samples from standard FMR. Higher-order effects due to parametric modulation of the magnetization dynamics, such as down-conversion, up-conversion, and frequency mixing, are observed, testifying the high sensitivity of this technique.

Theory of Field-Angle-Resolved Magnetoacoustic Resonance in Spin–Triplet Systems for Application to Nitrogen–Vacancy Centers in Diamond

Theory of Field-Angle-Resolved Magnetoacoustic Resonance in Spin–Triplet Systems for Application to Nitrogen–Vacancy Centers in Diamond

A NEW PATH MARKING TECHNOLOGY FOR LOCATING BURIED ASSETS BASED ON A NOVEL MAGNETO-MECHANICAL RESONATOR

One objective of this paper is to review the operating principle and intrinsic features of a magneto-acoustic or magnetomechanical resonator as it relates to using it for an electronic path marking solution for buried utilities. Magneto-mechanical resonators, in contrast with Electro-magnetic resonators, are easily scalable in length for tuning, consist of only two elements: Amorphous ribbon and Neodymium magnets inside a HDPE plastic case, with a long thin form factor that can be adhered to tape or conduits providing a lowest cost solution for marking the path of buried infrastructure. Path Marking electronic markers or tags, eliminate the need for access points which are used to applying a transmitter signal onto a tracer wire or a metallic cable before locating its path. Electronic marker resonators are passive (no battery) and always detectable above where they were buried, for over 50 years. This new advancement in buried resonator technology allows for a natural extension into remote sensing for buried utilities that can measure various attributes, such as: temperature, water presence, pressure or other, using the same locator technology. Path marking tags can be used in combination with Point RFID markers for advanced asset protection, asset management and mapping solutions.

Tunable Magnetoacoustic Oscillator with Low Phase Noise

A frequency-tunable low-phase-noise magnetoacoustic resonator is developed on the base of a parallel-plate straight-edge bilayer consisting of an yttrium-iron-garnet (YIG) layer grown on a substrate of a gallium gadolinium garnet (GGG). When a YIG-GGG sample forms an ideal parallel plate, it supports a series of high-quality-factor acoustic modes standing along the plate thickness. Due to the magnetostriction of the YIG layer the ferromagnetic resonance (FMR) mode of the YIG layer can strongly interact with the acoustic thickness modes of the YIG-GGG structure, when the modes' frequencies match. A particular acoustic thickness mode used for the resonance excitations of the hybrid magnetoacoustic oscillations in a YIG-GGG bilayer is chosen by the YIG-layer FMR frequency, which can be tuned by the variation of the external bias magnetic field. A composite scheme of a magnetoacoustic oscillator, which includes a FMR-based resonance preselector, is developed to guarantee satisfaction of the Barkhausen criteria for a single-acoustic-mode oscillation regime. The developed low-phase-noise composite magnetoacoustic oscillator can be tuned from 0.84 to 1 GHz with an increment of about 4.773 MHz (frequency distance between the adjacent acoustic thickness modes in a YIG-GGG parallel plate), and demonstrates the phase noise of $\ensuremath{-}116$ dBc/Hz at the offset frequency of 10 kHz.

Magneto-acoustic resonance in layered structure of ferrite and piezoelectric bimorph

The manuscript discusses a theoretical model that predicts a giant magnetoelectric (ME) coupling in laminates of ferrite and piezoelectric bimorph at the coincidence of electromechanical resonance for the electrical subsystem and ferromagnetic resonance for the ferrite. In such structures, the ME interaction is a result of mechanical strain. Using the piezoelectric bimorph gives rise to the excitation of high-order harmonic modes that are suppressed in ferrite-piezoelectric bilayers. ME coefficients, on the order of 590 V/A at 4.96 GHz, is predicted for the third resonance mode in laminate of yttrium-iron garnet and langatate bimorph. The phenomenon can be used for the realization of microwave sensors based on ME interaction.

Magnetoacoustic Resonance to Probe Quadrupole–Strain Coupling in a Diamond Nitrogen-Vacancy Center as a Spin-Triplet System

A theory of magnetoacoustic resonance is proposed to measure quadrupole-strain couplings in a spin-triplet state with the $C_{3v}$ point group symmetry, considering the spin-strain interaction in a diamond nitrogen-vacancy (NV) center. Based on the Floquet theory, we demonstrate how the single- and two-phonon transition probabilities depend on the change in the longitudinal and transverse quadrupole couplings, which can be controlled by rotating an applied magnetic field, around the threefold axis. The obtained quadrupole dynamics results are useful for realizing mechanical or ac strain-control of the NV spin as an alternative to the conventional magnetic control by spin resonance.

Damping of Magnetoelastic Waves

A general method for constructing a model of the dissipative function describing the relaxation processes induced by the damping of coupled magnetoacoustic waves in magnetically ordered materials has been developed. The obtained model is based on the symmetry of the magnet and describes both exchange and relativistic interactions in the crystal. The model accounts for the contributions of both the magnetic and elastic subsystems to the dissipation, as well asthe relaxation associated with the magnetoelastic interaction. The dispersion law for coupled magnetoelastic waves is calculated in the case of a uniaxial ferromagnet of the “easy axis” type. It is shown that the contribution of the magnetoelastic interaction to dissipative processes can play a significant role in the case of magnetoacoustic resonance.

Torsional modes in the magnetoelectric effect for a two-layer ferrimagnet-piezoelectric YIG / GaAs structure

The article is devoted to the theoretical study of the magnetoelectric (ME) effect in the magnetostrictive-piezosemiconductor structure of yttrium iron garnet (YIG) - gallium arsenide (GaAs) in the torsional mode. Earlier, it was found that the ME effect significantly increases with the transition from the low-frequency range to the region of electromechanical resonance (EMR). There are known results on the study of the ME effect in the range of different EMR modes: planar, flexural, and shear. This article proposes to consider the ME effect in the torsional mode region in a layered YIG-GaAs composite. Interest in this phenomenon is associated both with the study of the newest effect, and with the possibility of studying the ME effect in the region of magnetoacoustic resonance, i.e. when the torsional mode coincides with the spin wave in the region of ferromagnetic resonance. The results obtained can find application in the design of new ME devices.

High-frequency magnetoacoustic resonance through strain-spin coupling in perpendicular magnetic multilayers.

It is desirable to experimentally demonstrate an extremely high resonant frequency, assisted by strain-spin coupling, in technologically important perpendicular magnetic materials for device applications. Here, we directly observe the coupling of magnons and phonons in both time and frequency domains upon femtosecond laser excitation. This strain-spin coupling leads to a magnetoacoustic resonance in perpendicular magnetic [Co/Pd] n multilayers, reaching frequencies in the extremely high frequency (EHF) band, e.g., 60 GHz. We propose a theoretical model to explain the physical mechanism underlying the strain-spin interaction. Our model explains the amplitude increase of the magnetoacoustic resonance state with time and quantitatively predicts the composition of the combined strain-spin state near the resonance. We also detail its precise dependence on the magnetostriction. The results of this work offer a potential pathway to manipulating both the magnitude and timing of EHF and strongly coupled magnon-phonon excitations.

Analysis of Magnetoacoustic Quadrupole Resonance and Application to Probe Quadrupole Degrees of Freedom in Quantum Magnets

Motivated by the recent progress of high-frequency ultrasonic measurements, we propose a theory of magnetoacoustic resonance as a microscopic probe for quadrupole degrees of freedom hidden in magnetic materials. A local strain driven by an acoustic wave couples to electronic states of a magnetic ion through various quadrupole-strain couplings, and this provides a periodically time-dependent oscillating field. As a typical two-level system with the quadrupole, we consider a non-Kramers doublet and investigate single- and multiphonon-mediated transition processes on the basis of the Floquet theory. An analytic form of the transition probability is derived within the weak coupling theory, which helps us analyze the magnetoacoustic quadrupole resonance. We apply the theory to realistic non-Kramers doublet systems for the f2 configuration in Oh and D4h symmetries, and discuss how to identify the relevant quadrupole by controlling the quadrupole-strain coupling with an applied magnetic field in ultrasonic measurements.

Theory of Photon-Assisted Magnetoacoustic Resonance as a New Probe of Quadrupole Dynamics

Motivated by the recent progress of phonon-mediated control in quantum spin devices, we propose a possibility of hybrid measurement using electron paramagnetic resonance (EPR) and a surface acoustic wave (SAW). Considering quadrupole-strain (QS) couplings suggested for silicon vacancies, we present a minimum model of the two-level system to investigate a magnetoacoustic resonance (MAR) coupled to various strain modes driven by the SAW. The longitudinal and transverse QS couplings can be changed by rotating a magnetic field, which depends on a combination of the strain modes. Using the Floquet theory, we elucidate each coupling effect on the time-averaged transition probability, especially focus on a single-phonon transition process. The important result is that the longitudinal QS coupling brings about a sharp photon-assisted resonance and leads to an abrupt change in the field-angle dependent transition probability. Since this phonon transition process is always accompanied by the photon transition, the field angle for the sharp resonance peak can be detected by the EPR measurement. The hybrid EPR-MAR measurement is useful to confirm the existence of quadrupole degrees of freedom strongly coupled to elastic strains, and thus it is expected to be a complementary probe for the precise evaluation of quadrupole properties.

Contribution of Ukrainian Scientists to the Development of Electrodynamics

The aim of the paper is to prove the importance of the works performed by Ukrainian scientists for the development of electrodynamics. Some examples of achievements made by Ukrainian scientists in this scientific area include physical theories in such directions as the electrical conductivity, domain structure of ferromagnets, photoelectromotive force in semiconductors, microscopic theory of superconductivity, Shubnikov–de Haas effect, magneto-acoustic resonance, invention of an electric tram, live broadcast of the moving-image signal, distant control of objects by means of radio signals, and arc welding of metals. Most Ukrainian scientists have founded their own scientific schools, which works are recognized throughout the world. They were not only engaged in the scientific and lecturing activities, but also in the popularization of science, reformation of the education system, and social activity.

Experimental Study of Magneto-Acoustic Resonance in the System of a Ferrite Circuit

The effect of magneto-acoustic resonance is studied experimentally in the system of a ferrite circuit. The strong effect the resonant circuit has on the quality of magneto-acoustic resonance is determined. The effect of autogeneration can be used for experimental investigations of nonlinear ferromagnetic resonance in the far cutoff range in the primary and secondary resonances in a ferrite sample.

Magnetoelectric Composites: Modeling and Application

The progress in electronic technology is directly coupled with the advances made in materials science. Within the broad class of materials available today, functional materials provide unique opportunity for developing novel components and devices as their physical and chemical properties. A combination of ferromagnetic and ferroelectric materials provides a new class of functional materials, termed as magnetoelectrics. An overview of modern magnetoelectric composites and examples of the design of electronic devices based on them are presented. The feature of these materials is that their parameters changes under the influence of an external magnetic and electric fields. The behavior of magnetoelectric composites in the wide frequency range is considered. Modeling of ME composites at low frequencies and in the field of electromechanical, ferromagnetic and magnetoacoustic resonances has shown that they can be effectively used to design various electronic devices in a wide frequency range. Nomographs method which can be used to plot the ME parameters versus initial material parameters and component volume fractions is presented. Nomographs can be used for a quick test of ME composites for applications where an approximate answer is appropriate and useful. Examples of ME composites application such as: magnetic field sensors, current sensors, microwave phase shifters, filters, attenuators, isolators are presented.

Magneto-Acoustic Resonator for Aquatic Animal Tracking

Over the past three decades, passive acoustic telemetry has significantly helped marine scientist to study and understand the spatial ecology, migratory behaviors, and mortality rates of aquatic animals. A popular telemetry system consists of two components: an acoustic transmitter tag attached to an aquatic animal and powered by a small battery, and a stationary station that receives the acoustic signals from the tagged animal and determines its location. The added weight and increased size of the tag introduced by the battery limit the implementation of this system to relatively large animals. Moreover, these tags have a limited operational time determined by the lifetime of the battery in combination with the measurement frequency and data resolution and transfer rate. In this paper, a self-powered magneto-acoustic resonator for animal tracking is proposed. It is achieved by utilizing the low-frequency motions of the animals to excite high-frequency acoustic pulses. The measurement results show that the device is capable of producing an average acoustic sound of 55 dB sound pressure level at 1 m of distance with a resonant frequency of 15 kHz.

A Chaotic Magnetoacoustic Oscillator with Delay and Bistability

We present experimental data on the development of chaotic oscillations in a nonautonomous magnetoacoustic oscillator based on a hybrid magnetoacoustic resonator of the reflection type. The proposed oscillator exhibits regimes of quasi-periodic and chaotic generation under an external low-frequency periodic force. The chaotic dynamics of the magnetoacoustic oscillator is caused by the presence of delay and bistability in the system.