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Background and Objectives: One of the main tasks for developing magnonic devices is to form and control spin wave beams. For this purpose, the decoration of ferrite films with magnetic or non-magnetic metal areas can be used. The aim of this work is to study the peculiarities of magnetostatic surface wave (MSSW) propagation in the channels formed in yttrium-iron garnet (YIG) films by deposition of 1.5 μm thick metal decorations from chromium (Cr) and permalloy (Py). Materials and Methods: Studied samples were fabricated on the base of 6.5 μm-thick epitaxial YIG film by the DC magnetron sputtering, photolithography, and ion etching techniques. Frequency dependencies of magnitude and phase of the transmitted MSSW signal at different applied magnetic field were measured with the help of a vector network analyzer and a microwave probe station. Calculation of the dispersions and insertion losses for MSSW propagating in the metallized YIG film was performed on the basis of Maxwell’s equations in the magnetostatic approximation, the Landau-Lifshitz equation, and standard electrodynamic boundary conditions. Results and Conclusion: The optimal channel width w relative to the antenna aperture providing channeling of the MSSW signal with the possibility of “antireflective effect” for the transmitted signal has been found to be w = 200 μm. It has been shown that for the formation of channeling effect, one needs to use a non-magnetic metal with the thickness leading to a transition to the “metallic” branch of the MSSW dispersion or a magnetic metal with the thickness resulting in bending of a short-wavelength part of MSSW dispersion. For the studied samples, it is d(Cr) = 1.5 μm and d(Py) = 30 nm, respectively. The obtained results demonstrate the possibility of using the channels in metallic decorations for the formation of directed spin wave beams.

In this paper, the theory, micromachining technology, and experimental results of the coupling of integrated magnetic film-based resonators for microwave signal filtering are presented. This is an extended contribution to the field of magnetostatic wave coupled resonators, including details about the technological results, circuit theory, and perspective applications for tunable integrated coupled magnetic resonators. An analytical approach using the magnetostatic wave approximation is used to derive the coupling coefficient between adjacent resonators coupled by the electromagnetic field decaying outside the resonators. Then, micromachining employing hot phosphoric acid etching is presented to manufacture integrated coupled resonators. Finally, circuit modeling and experimental results obtained using the ferromagnetic resonance technique are discussed. [ABSTRACT FROM AUTHOR]

A specially designed metamaterial was investigated wherein the top metasurface was comprised of MgF2-graphene periodic nanopillers formed over an InSb nanolayer. The transmission characteristics of metamaterial was artificially controlled, and the effects due to altering external stimuli, such as thermal ambience, graphene chemical potential and magnetostatic bias, were studied in the 6–15 THz regime. The structure exhibits vanishing transmission with sharp (transmission) minima in certain frequencies, the positions of which essentially depend on the external stimuli. The angular dependence and polarization-insensitive properties were also discussed, apart from the effect of using different numbers of graphene layers in the nanopillers. The results show potential of the metamaterial as sensor due to the thermal, electrical and magnetic variations. [ABSTRACT FROM AUTHOR]

In this paper, the theory, micromachining technology, and experimental results of the coupling of integrated magnetic film-based resonators for microwave signal filtering are presented. This is an extended contribution to the field of magnetostatic wave coupled resonators, including details about the technological results, circuit theory, and perspective applications for tunable integrated coupled magnetic resonators. An analytical approach using the magnetostatic wave approximation is used to derive the coupling coefficient between adjacent resonators coupled by the electromagnetic field decaying outside the resonators. Then, micromachining employing hot phosphoric acid etching is presented to manufacture integrated coupled resonators. Finally, circuit modeling and experimental results obtained using the ferromagnetic resonance technique are discussed.

Background and Objectives: Magnetic thin film waveguides of a finite width are considered as the main building blocks for magnonic circuits where the magnetostatic waves are the information carriers. The purpose of this study is to investigate experimentally the effects of the waveguides width, position of microantennas for excitation and detection of the magnetostatic waves, coupling between the waveguides on excitation and transmission characteristics of the magnetostatic waves for the waveguides with the width of ~10 μm based on an yttrium iron garnet film (material that has the lowest magnetostatic wave damping among all known magnetic materials). Materials and Methods: A set of the microwaveguides with the specified width of 15, 10 and 5 μm and with different position of the microantennas integrated with the waveguide as well as systems of two close parallel waveguides with the microantennas was fabricated out of 0.9 μm thick yttrium iron garnet film using photolithography, ion etching and magnetron sputtering. Measurements of the transmission and reflection coefficients as a function of the frequency were performed by a vector network analyzer along with a microwave probe station. The bias field was applied tangentially along or perpendicular to the waveguide. Results and Conclusions: It is found that the used technology provided ~70° tilt of the waveguides sidewalls from the vertical direction. It is also revealed that placing the microantennas near the ends of the waveguides reduces the efficiency of excitation of the long-wavelength part of the magnetostatic waves spectrum. In addition, such an arrangement of antennas was characterized by the absence of the features associated with the excitation of the magnetostatic wave width modes. The latter effect can be used for filtering the width modes if necessary. It is shown that, for ~15 μm wide waveguides based on 0.9 μm thick yttrium iron garnet film, there is a significant (~0.5 GHz) overlap of the spectra of the fundamental modes of magnetostatic surface wave and magnetostatic backward volume wave in transversely and longitudinally magnetized microwaveguides, respectively, at the bias field in the range of 0.5–1.5 kOe. This width can be considered close to optimal for constructing structures from orthogonal waveguides based on such thick yttrium iron garnet films. A further decrease in the width leads to an undesirable decrease in the transmission coefficient. In addition, in this case, the shape anisotropy effect can be excessively strong and move a part of the magnetostatic surface and backward volume waves spectra, narrowing the region of their overlap. It is also shown that for two parallel microwaveguides with a width and distance between them Твердотельная электроника, микро- и наноэлектроника 251 of ~15 μm, the excitation of the magnetostatic wave in one of them leads to energy transfer to the adjacent waveguide with an efficiency of ~ -10–15 dB due to the coupling between the waveguides. This effect must be taken into account when miniaturizing magnonic networks.

The investigation addresses the magnetostrictive sensor (MsS) signal received from pipes of different materials using an amorphous alloy as a sensor element. This sensing system also acts as a transducer to generate ultrasonic waves which appear as echoes from pipe end and defect. The static magnetic field revealed different MsS signals from magnetically different pipes, viz., aluminum (nonmagnetic), galvanized iron (nonmagnetic coating), and mild steel (magnetic) pipes. Applied static field enhanced MsS signals in all the pipes. The extent of this enhancement is influenced by transduction efficiency of the MsS transducer. This efficiency varied with the magnetic nature of the pipe. Simulation through COMSOL Multiphysics elucidated the magnetic flux intensity patterns in these pipes and the consequent behavior of MsS transducer in inspection of pipes of different materials. The study indicated the role of static magnetic field in an MsS transducer for structural health monitoring (SHM) of pipes used prevalently in domestic and industrial sites. [ABSTRACT FROM AUTHOR]

In this letter, a theoretical expression for forward volume spin wave (FVSW) transducer radiation resistance is proposed to encompass the effects of transducer metal thickness. This thickness effect results in a reduction of radiation resistance that scales with metal thickness. The reduction in radiation resistance is especially evident in transducers with metal thicknesses approaching the wavelengths of the spin waves launched. A method that decomposes the current source launching spin waves into a series of orthogonal functions that correspond to the FVSW thickness modes is used to evaluate the expression for the radiation resistance. Five different spin wave transducers with metal thicknesses of 0.1, 0.3, 0.5, 0.7, and $0.9 {\mu }m$ were simulated in HFSS (using a magnetostatic approximation) and their resultant radiation resistances and radiation efficiencies confirm the theoretical expression. [ABSTRACT FROM AUTHOR]

We study the magnetization dynamics in La-doped yttrium iron garnet thin film induced by a slot line waveguide with the magnetic field applied perpendicular to the plane. The magnetization dynamics depend significantly on the slot line waveguide dimensions, particularly the number of excitation conditions increases with the enlargement of linewidth and the gap between the lines. Such an increase is not observed when the magnetic field is applied to the film plane. The excitation is caused by the interaction between the local magnetization dynamics around the line and the spin waves coming from the other side of the line. Forward volume magnetostatic spin waves are emitted when the magnetic field is applied perpendicular to the film. Their magnetic field dependence of the wavelength change is very gradual, allowing the satisfaction of the resonance condition to be much easier than the in-plane magnetized film. [ABSTRACT FROM AUTHOR]

The phase is one of the fundamental properties of a wave that allows to control interference effects and can be used to efficiently encode information. We examine numerically a magnonic resonator of the Gires–Tournois interferometer type, which enables the control of the phase of spin waves (SWs) reflected from the edge of the ferromagnetic film. The considered interferometer consists of a Py thin film and a thin, narrow Py stripe placed above its edge, both coupled magnetostatically. We show that the resonances and the phase of the reflected SWs are sensitive for a variation of the geometrical parameters of this bi-layered part of the system. The high sensitivity to film, stripe, and non-magnetic spacer thicknesses offers a prospect for developing magnonic metasurfaces and sensors. [ABSTRACT FROM AUTHOR]

In this article, we experimentally demonstrate the propagation of magnetostatic surface spin wave (MSSW) in the orthogonally joined yttrium iron garnet stripes in the form of T-shaped connection. By the means of microwave spectroscopy technique, we show how the transmission is affected by the distance between orthogonal yttrium iron garnet stripes. Micromagnetic modeling demonstrates the presence of nonreciprocal propagation of spin waves (SWs) between all three ports of the T-junction. A mechanism for controlling the spatial-frequency selection of a propagating signal by variation of the air gap in the area of connected orthogonal sections is shown. The proposed structure can act as a magnonic splitter for 3-D topology of multilevel magnonic networks (MNs). The transition to a multilayer topology of MNs opens the possibility of increase of the packing density of computational units based on the principles of magnonics. [ABSTRACT FROM AUTHOR]

Here, we present the results of an experimental and numerical study of controllable spin-wave propagation in the yttrium iron garnet stripe with an Fe-Rh slab. The transformation of spin-wave dispersion and transmission are observed by the focusing laser light on top of the Fe-Rh slab. It was shown that the geometry variation and design of the Fe-Rh slab significantly affect spin-wave propagation. The static internal magnetic field profile in the yttrium iron garnet is subject to position and the geometric parameters of the Fe-Rh slab. Additionally, the possibility of width mode filtering was shown for a surface magnetostatic spin wave by the means of micromagnetic simulation. The qualitative correspondence between the behavior of spin waves in the numerical simulation and microwave spectroscopy data was observed. The proposed structure can be used as a functional unit with the simultaneous frequency selective and spin-wave mode filtration regime in planar magnonic networks. [ABSTRACT FROM AUTHOR]

A $k$ -space approach for magnetostatic field computation in magnetic thin films is proposed. The convolution of truncated Green’s function and the magnetization field is computed via the fast Fourier transform, where the discretization process is done in the $k$ -space (Fourier space) instead of the ordinary space. In this respect, removal of the influence of replica in the ordinary space when the magnetostatic field is reconstructed is achieved. The accuracy and the efficiency of the proposed approach are investigated. [ABSTRACT FROM AUTHOR]

We acquire ferromagnetic resonance (FMR) spectra for an out-of-plane magnetized yttrium iron garnet sample with a vector network analyzer at microwave frequencies ranging from 4.2 to 5.2 GHz. The applied static magnetic field varies from approximately 253.6 to 260.1 kA/m. Based on an empirical model for resonant features in the S21 spectrum produced by the excitation of multiple modes and instrumental effects, we predict measured values of S21-parameters. For each of many microwave frequencies, for each of multiple modes, we determine the resonant field value of the applied magnetic field, an amplitude, and an FMR linewidth. Based on the frequency-dependent resonant field values produced by excitation of the main mode, we determine the effective magnetization and the gyromagnetic ratio of the sample. [ABSTRACT FROM AUTHOR]

By their very nature, spin waves (SWs) with different frequencies can propagate through the same waveguide, while mostly interfering with their own species. Therefore, more SW encoded data sets can coexist, propagate, and interact in parallel, which opens the road toward hardware replication-free parallel data processing. In this article, we take advantage of these features and propose a novel data parallel SW-based computing approach. To explain and validate the proposed concept, byte-wide 2-input XOR and 3-input majority gates are implemented and validated by means of Object-Oriented MicroMagnetic Framework (OOMMF) simulations. Furthermore, we introduce an optimization algorithm meant to minimize the area overhead associated with multifrequency operation and demonstrate that it diminishes the byte-wide gate area by 30% and 41% for XOR and majority implementations, respectively. To get inside on the practical implications of our proposal, we compare the byte-wide gates with conventional functionally equivalent scalar SW gate-based implementations in terms of area, delay, and power consumption. Our results indicate that the area optimized 8-bit 2-input XOR and 3-input majority gates require 4.47x and 4.16x less area, respectively, at the expense of 5% and 7% delay increase, respectively, without inducing any power consumption overhead. Finally, we discuss factors that are limiting the currently achievable parallelism to 8 for phase-based gate output detection and demonstrate by means of OOMMF simulations that this can be increased 16 for threshold-based detection-based gates. [ABSTRACT FROM AUTHOR]

In this article, we explain the important effect of varying parameter of staggered undulator on inverse free electron laser (IFEL) accelerator. The modified IFEL equations are derived and analyzed. The synchrotron radiation losses that give rise to saturation length and maximum energy are included in the analysis. Both saturation length and maximum energy of the IFEL are influenced by the pole to pole gap and the periodic length of the staggered undulator. [ABSTRACT FROM AUTHOR]

Demagnetization in a thin film due to a terahertz pulse of magnetic field is investigated. Linearized Landau-Lifshitz-Gilbert (LLG) equation in the Fourier space to describe the magnetization dynamics is derived, and spin wave time evolution is studied. Finally, the demagnetization due to spin wave dynamics and recent experimental observations on similar magnetic system is compared. As a result, the marginal role of spin wave dynamics in loss of magnetization is established. [ABSTRACT FROM AUTHOR]

The nonreciprocal bandpass filter has been achieved by utilizing the nonreciprocity characteristics of the magnetostatic surface wave (MSSW) in planar ferrite slabs. In this article, the dispersion relation, impedance, and attenuation of MSSW between the pure and metallized ferrite slabs have been analyzed and compared. Theoretical analysis indicates that the ferrite slab metallized by a thin conductive layer would introduce significant attenuation on the metallized interface, which is MSSW propagating on the isolated direction, while MSSW on the other surface is barely affected. Therefore, nonreciprocal bandpass filter with enhanced isolation can be achieved with metallized ferrite slab. Simulated S-parameters show that a notch in the isolating direction can be obtained at the passing band of the transmitting direction. Experimental results show that the nonreciprocal filter with metallized yttrium iron garnet (YIG) slab (by depositing 100- $\mathbf {nm}$ copper film) exhibits more than 10-dB higher isolation than that with pure YIG slab, while the center frequency, insertion loss, and 3-dB bandwidth maintain almost the same. The center frequency of the filter with metallized YIG slab can be tuned from 7.26 to 8.38 GHz with insertion loss of less than 3 dB, and in-band isolation of more than 30 dB as the dc bias magnetic field is increased from 1.8 to 2.3 kOe. Besides, the nonreciprocal filter has ultra-wide out-band suppression since it utilizes the narrow frequency band of MSSW. The −10-dB out-band rejection exceeds 36 GHz in the upper band and 1 MHz in the lower band. [ABSTRACT FROM AUTHOR]

Since few decades, research in the magnonic area, which studies the phenomenon of spin waves propagation in magnetic materials, has grown simultaneously with the emergence of the so-called spintronic and nano-structured magnetic materials. Recent works exposed the interest of such devices for designing magnetic field sensors, considering the dependence of the transmission parameter $\underline {S_{21}}$ regarding the external applied magnetic field, for excitation frequency of several GHz. In this paper, we have investigated the ability of spin wave propagation phenomenon to be used as a magnetometer by characterizing its expected performances, particularly the output sensitivity, expressed in unit of V/T. The sensing element is designed from a YIG film (10 mm $\times5$ mm $\times 19.4\,\,\mu \text{m}$) deposited on GGG substrate. It is placed on a microstrip antenna transducer made of two copper lines, respectively to excite and measure the spin waves. The excitation is provided by a sine electromagnetic wave at a fixed frequency ${f}_{0}=1.146\,GHz$. The induced spin waves propagate along the main length direction of the YIG material and induce a voltage signal at the output antenna at the carrier frequency ${f}_{0}$. When the external DC magnetic field varies, it yields a modulated signal. The dedicated and reduced electronic conditioning circuitry, based on a I/Q quadrature demodulator, allows to extract the field variations information with an output sensitivity of about $20\,V/T$. Considering that the dominating noise sources are those due to the electronic conditioning circuitry, a sensor equivalent magnetic noise level of several $nT/\sqrt {Hz}$ in white noise region was obtained. [ABSTRACT FROM AUTHOR]

We have designed, fabricated, and characterized magnetostatic wave (MSW) resonators on a chip. The resonators are fabricated by patterning single-crystal yttrium iron garnet (YIG) film on a gadolinium gallium garnet (GGG) substrate and excited by loop-inductor transducers. We achieved this technology breakthrough by developing a YIG film etching process and fabricating thick aluminum coplanar waveguide (CPW) inductor loop around each resonator to individually address and excite MSWs. At 4.77 GHz, the 0.68-mm2 resonator achieves a quality factor (${Q}{)} > {5000}$ with a bias field of 987 Oe. We also demonstrate YIG resonator tuning by more than one octave from 3.63 to 7.63 GHz by applying an in-plane external magnetic field. The measured quality factor of the resonator is consistently over 3000 above 4 GHz. The micromachining technology enables the fabrication of multiple single- and two-port YIG resonators on the same chip with all resonators demonstrating octave tunability and high ${Q}$. [ABSTRACT FROM AUTHOR]

A vibration energy harvester (VEH) converts the kinetic energy of a moving source into electrical energy. In this article, we consider a 1-D electromagnetic vibration energy harvester (1-D EMVEH) that consists of three coaxial cylindrical permanent magnets enclosed in a tube such that the middle magnet is levitating. The resulting movement of the middle magnet can then induce an electromotive force (EMF) in one or more surrounding coils. Using an analytical model, we derive expressions for the 1-D-EMVEHs characteristic frequency and output power by using the Fourier space approach. First, the magnetostatic energy of the system as a function of the position of the levitating magnet is calculated. Its spatial gradient gives the force acting on a magnet, which drives its dynamics. Next, more accurate magnetic flux and EMF expressions are obtained. The results are compared with experimental measurements, revealing an excellent agreement. [ABSTRACT FROM AUTHOR]

The relationship between magnetoelectricity and electromagnetism is a subject of a strong interest and numerous discussions in microwave and optical wave physics and material sciences. The definition of the energy and momentum of the electromagnetic (EM) field in a magnetoelectric (ME) medium is not a trivial problem. The question of whether electromagnetism and magnetoelectricity can coexist without an extension of Maxwell's theory arises when the effects of EM energy propagation are studied and the group velocity of the waves in an ME medium is considered. The energy balance equation reveals unusual topological structure of fields in ME materials. Together with certain constraints on the constitutive parameters of a medium, definite constraints on the local field structure should be imposed. Analyzing the EM phenomena inside an ME material, the question "what kind of the near fields arising from a sample of such a material can be measured?" should be answered. The visualization of the ME states requires an experimental technique that is based on an effective coupling to the violation of spatial as well as temporal inversion symmetry. To observe the ME energy in a subwavelength region, it is necessary to assume the existence of first‐principle near fields—the ME fields. These are non‐Maxwellian near fields with specific properties of violation of spatial and temporal inversion symmetry. A particular interest to the ME fields arises in studies of metamaterials with "artificial‐atoms" ME elements. [ABSTRACT FROM AUTHOR]

Absorptive-type ferrite-based frequency-selective limiters (FSLs) utilize nonlinear (NL) phenomena in magnetized ferrites to provide real-time analog signal processing of RF/microwave electromagnetic (EM) signals. There are no commercially available modeling tools that simulate these interactions, and the development and optimization of FSLs are largely done experimentally. FSL modeling and design is complicated by NL, multiscale, and multiphysics nature of operation. In this article, an NL loss model in a ferrite is proposed and implemented in an efficient numerical algorithm. The equivalent linear magnetic loss tangent is represented in a closed form. A full-wave numerical EM model with high-fidelity meshing is set up so that material properties are assigned to each mesh element and are iteratively adjusted depending on the local magnetic field. The numerical model is sliced along the EM wave propagation, and an NL eigenvalue is obtained for each slice as a function of frequency, power, and external magnetic bias field and stored in lookup tables. The slices are cascaded, and power attenuation is calculated with loss changing along the wave path according to the lookup tables. The resulting data are processed to be suitable for equivalent circuit models. Numerical results for coplanar waveguide FSL are validated by measurements. The proposed modeling approach is useful for engineering FSL devices. [ABSTRACT FROM AUTHOR]

Gyrotrons are high-frequency, high-power microwave sources with potential applications in plasma generation, energy generation, spectroscopy, and security. The Department of Science and Technology initiated the development of a 42 GHz, 200 kW, continuous wave (CW) gyrotron for the Indian Tokamak system through a multi-institutional project. The activity is targeted toward indigenous development of India’s first high-power gyrotron. In gyro-devices, frequency of operation is determined by the cyclotron frequency, and thereby the magnetic field. The development of a high-field intensity normal conducting cavity magnet was an imperative step during the testing and integration of the gyrotron tube assembly to achieve the desired beam transmission with a moderate operating cost. A high and spatially homogeneous magnetic field (1.61 T) is required to be established in the beam–wave interaction region by the cavity magnet. The desired magnetic field, as a function of axial distance from the gun to the collector, is governed by the requirements of gun optics, focusing field in the interaction region, and the adiabatic expansion of the beam into the collector. A water cooled electromagnet has been designed to produce the requisite magnetic field in the cavity region over an axial length of 40 mm with field homogeneity better than ±0.35%. Magnet design was optimized to meet the field requirements in the cavity and cathode gun. Magnetic field simulations were carried out in conjunction with the electrostatic field and space charge analysis. This paper presents finite element computations, design optimization, development and testing of a continuous duty iron core electromagnet for a first harmonic interaction mode (TE03) gyrotron cavity. Magnetic, electrical, thermal, and hydraulic design of the electromagnet is discussed in this paper. [ABSTRACT FROM AUTHOR]

Ferrite isolators are attractive due to their excellent isolation, low loss, good linearity, and high-power performance. However, these devices usually operate over a single-frequency band. Multiband applications are possible if the isolation bandwidth of an isolator can be tuned. This paper presents a tunable waveguide-based full-mode ferrite isolator as well as a more compact half-mode tunable isolator, both fabricated on yttrium-iron-garnet substrates. For the first time, theory and design guidelines for the center frequency, bandwidth, and tuning of the ferrite isolators’ unidirectional magnetostatic surface wave (MSW) mode are presented. The proposed theoretical model reveals that the isolation bandwidth can exceed 100% if the magnetization-to-bias field ratio is higher than 8. Although the full-mode design is fabricated using a conventional subtractive technique, the half-mode design is implemented using inkjet printing technology. The full-mode isolator provides a maximum bandwidth of 45% and a peak isolator figure of merit (IFM) of over 65 dB at 7 GHz, whereas the half-mode design has a maximum bandwidth of 59% and a peak IFM of 76.7 dB at 7.5 GHz. The tuning of the center frequency is from 7 to 10.7 GHz for the full-mode and from 4.4 to 9.9 GHz for the half-mode design using magnetic field strengths up to 2500 and 2400 Oe, respectively. This paper demonstrates the versatility of ferrite isolators as tunable microwave devices for reconfigurable RF applications. [ABSTRACT FROM AUTHOR]

This paper reports on the experimental measurement of power threshold levels for the multipactor effect between samples of ferrite material typically used in the practical implementation of L- and S-band circulators and isolators. For this purposes, a new family of wideband, nonreciprocal rectangular waveguide structures loaded with ferrites has been designed with a full-wave electromagnetic simulation tool. The design also includes the required magnetostatic field biasing circuits. The multipactor breakdown power levels have also been predicted with an accurate electron tracking code using measured values for the secondary electron yield (SEY) coefficient. The measured results agree well with simulations, thereby fully validating the experimental campaign. [ABSTRACT FROM AUTHOR]

This paper describes 3-D numerical simulations and radio frequency (RF) measurements of wave propagation in microwave-heated magnetized plasmas of ion sources. Full-wave solution of Maxwell’s equations has been addressed through the finite-element method commercial software COMSOL. Our numerical model takes into account the strongly inhomogeneous and anisotropic magnetized “cold” plasma medium. The simulations reproduce the main features of the wave–plasma interaction of the flexible plasma trap (FPT) that recently came into operations at INFN-LNS. A two-pin RF probe has been ad hoc developed and used as a plasma-immersed antenna for measuring local wave electric fields in the FPT device. The measurements of plasma electron density and RF electric field, performed for different external magnetic field configurations, allowed direct comparison with the assumed simulation model. [ABSTRACT FROM AUTHOR]

We demonstrate that micrometer-scale spin waves can be excited in a thin film of the ferrimagnetic material yttrium iron garnet (YIG) using patterned, multi-element antennas. The magnitude of the dynamic magnetic field generated by such antennas decays exponentially along the thickness direction, and this leads to an enhanced coupling to modes having a surface-like character as opposed to a more sinusoidal bulk-like character. We have used this property to identify spin waves having a mixed bulk/surface character. [ABSTRACT FROM AUTHOR]

This letter presents a thin dielectric sheet (TDS) method for the analysis of electrostatic or magnetostatic biased graphene. As the conductivity of graphene under magnetostatic bias is a tensor, this TDS is proposed to analyze this anisotropic medium. In addition, the TDS method only needs to mesh the surface of the target while the volume integral equation method needs especially fine mesh, which will cost a large consumption of time and memory. Numerical examples are demonstrated to further validate the accuracy and efficiency of the TDS method. [ABSTRACT FROM AUTHOR]

The problem of kinetic thermal effect on propagation characteristics of electromagnetic (EM) radiation incident on a hot Maxwellian magnetoplasma slab near a metallic surface is investigated. Reflection, absorption, and transmission rates are calculated numerically for a set of parameters that may be suitable for stealth plasma together with other applications. Numerical results, compared with those obtained using cold and warm plasma fluid models, show thermal enhancement of absorption of a transverse right circularly polarized EM wave propagating along an applied magnetostatic field within a slab of Vlasov plasma. Propagation characteristics of the right circular wave with a full kinetic expression for the refractive index are recovered in the limiting cases of magnetically biased cold and warm plasmas. [ABSTRACT FROM AUTHOR]

Electric field control of dynamic spin interactions is promising to break through the limitation of the magnetostatic interaction-based magnetoelectric (ME) coupling effect. In this paper, electric field control of the two-magnon scattering (TMS) effect has been demonstrated in Ni0.5Zn0.5Fe2O4/Pb(Mn2/3Nb1/3)-PbTiO3 (001) multiferroic heterostructure. The TMS effect is an extrinsic magnetic damping mechanism that scatters the uniform spin motions excited by ferromagnetic resonance (FMR) into degenerate states of spin waves, offering a framework for voltage control of spin dynamics and further increase the ME effect. The angular dependence FMR measurement has been performed by the electron paramagnetic resonance spectrometer. A large electric field modulation of FMR field (−347 Oe) and FMR linewidth (275 Oe) is achieved at the TMS angle of $\theta _{H} = 60 {^{\circ }}$. Particularly, the TMS effect contribute to ME coupling at the critical TMS angle is about 194% in magnitude compared with that of the strain effect-mediated ME coupling. The TMS intensity is increased by 14.5% under electric field at room temperature. [ABSTRACT FROM AUTHOR]

A theoretical account is given for the non-classical properties of magnons in ultra-thin ferromagnetic films with in-plane magnetization under the conditions of parallel pumping. A microscopic or Hamiltonian-based approach with a lattice of effective spins interacting through the magnetic dipole–dipole and exchange interactions is used. With the Zeeman energies of the static applied field and the microwave pumping field included, the total Hamiltonian is transformed from spin operators to boson creation and annihilation operators. Using a representation of coherent magnon states, we obtain the explicit results for the temporal evolution of the magnon occupation number as well as the magnon squeezing. In particular, it is shown that the manipulation of the collapse-and-revival phenomena for the average number of magnons and the properties of the magnon squeezing is made possible by controlling the nonlinearity in the system through the microwave pumping field. [ABSTRACT FROM AUTHOR]

Rigorous magnetodynamic (MD) study presented in this paper reveals what seems to be the real nature of ferromagnetic resonances occurring in gyromagnetic samples situated in larger resonant cavities. Experiments were performed with cylindrical and spherical YIG samples inserted into either cylindrical dielectric resonator or typical rectangular cavity. It is shown that the dominant mode present in the YIG sample, which was identified as the \text HE111^{+} mode, satisfies the magnetic plasmon resonance condition defined by the effective permeability \mu r\approx {-1} for cylindrical samples or \mu r\approx {-2} for spherical samples. Experiments confirmed the existence of surface resonances, identified as magnetic plasmons, and volume resonances. Comparison between the MD model, the quasi-magnetostatic model, and the perturbation theory was performed and limitations of the approximate approaches are shown. [ABSTRACT FROM PUBLISHER]

This study of the spin waves coupling in the magnonic coupler, formed by the laterally coupled magnonic stripes, is performed by the means of finite-element and micromagnetic simulations. The efficiency of the spin-wave coupling is improved by the geometry design and choice of the appropriate magnetization direction inside each magnonic stripe. The proposed side-coupled magnetic stripes enable the improvement of performance of the advanced integrated magnonic devices and offer a range of further opportunities in planar magnonics. [ABSTRACT FROM AUTHOR]

We report on the theoretical study of magnetostatic surface wave propagation through the two side-coupled 1-D magnonic crystals (MCs) with broken translational symmetry. Using the transfer matrix method, we obtained transmission and reflection coefficients. Existence of two defect modes in such four-port planar structure was shown. We consider the possibility of controlling the position of defect modes by changing coupling between MCs. Comparison between investigated structure with coupled defect-free magnonic crystals was provided. [ABSTRACT FROM AUTHOR]

The present study theoretically investigates for the localized magnetic polaritons at the junction of two antiferromagnetic superlattices coupled by the antiferromagnetic film in the presence of external magnetic field. The calculation of the localized magnetic polariton (surface-guided) modes proceeds by solving full Maxwell's equations with electromagnetic boundary conditions at the junction with the antiferromagnetic film. We use the effective medium theory in the framework which the antiferromagnetic superlattice behaves like an anisotropic bulk medium. The influence of the external magnetic field on the spectrum of surface-guided polaritons and the dependence on the physical properties of the contact film were investigated numerically for various antiferromagnetic systems. The results obtained in this study will facilitate the development of engineering applications, such as waveguide devises. [ABSTRACT FROM AUTHOR]

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Excitation of non-reciprocal magnetostatic surface wave (MSSW) has been studied in an ultra-thin yttrium iron garnet (YIG) film. The YIG films were grown on a gadolinium gallium garnet (111) substrate using pulsed laser deposition. The films exhibit an exceptional crystalline quality and an extremely low magnetic damping at radio frequency and microwave. Non-reciprocal MSSWs in a 20-nm-thick YIG film has been observed using a coupled coplanar waveguide structure with a shared common ground. Increase of the YIG film thickness to 190 nm, the non-reciprocity has been significantly enhanced, resulting in a maximum 10-dB amplitude gain and 55.5° phase shift in 30-mT magnetic field between the MSSWs traveling in opposite directions. In the absence of magnetic field, the device shows a reduced amplitude gain of 2 dB and a phase shift of 15.8°. These results can find broad applications in building self-biased spin-wave-based components in integrated signal processing and communication system. [ABSTRACT FROM PUBLISHER]

Dipolar spin-wave coupling in the lateral topology of adjacent magnonic stripes is studied. Two laterally parallel dipolarly coupled yttrium-iron garnet magnonic waveguides were considered. The periodic power transfer at a distance equal to the coupling length from one stripe to the other stripe was demonstrated. By means of finite-element and micromagnetic numerical simulation, the dispersion and transmission spectra of spin waves were obtained. The coupling length is determined by variation of the static magnetization angle. The lateral magnonic stripes can be used as a functional unit in planar magnonic networks as a directional coupler, spin-wave multiplexer, and microwave power divider. [ABSTRACT FROM PUBLISHER]

Magnetostatic surface wave propagation was measured in an yttrium-iron garnet film with a subwavelength, micrometer-sized, periodic array of etched grooves. There were regions with anomalous dispersion and rejection bands in the frequency dependence of the transmission characteristic. Their number and bandwidth changed depending on the angle between the directions of the bias magnetic field and the grooves. [ABSTRACT FROM PUBLISHER]

We demonstrate how a unique nanomodulation within a continuous ferromagnetic film can induce magnetic dipoles at predefined, submicrometer scale locations, which can tune the global magnetic properties of the film due to dipole-dipole interactions. Arrays of tunable magnetic dipoles are generated with in-plane and out-of-plane directions, which can be rotated in-plane within the three-dimensional (3-D) modulated structure of a continuous film. In-plane magnetic dipole rotation enables a methodology to control overall magnetic properties of a ferromagnetic thin film. Formation of magnetic dipoles and their tunability were studied in detail by magnetic force microscopy, high-resolution magnetic measurements, and micromagnetic simulation of a nanomodulated Ni45Fe55 alloy film. A pattern larger than a single magnetic domain would normally form a vortex in the remanent state. However, here the unique 3-D nanostructure prevents vortex formation due to the competition between in-plane and out-of-plane dipole-dipole interaction giving rise to a metastable state. Experimentally, at zero remanence, the magnetization goes through a transformation from a metastable to a stable state, where the dipole-dipole interaction depends on their geometrical arrangement. Thus, the magnetic properties of the continuous film can be varied by the proposed pattern geometry. A detail analytical study of the dipolar energy for the system agrees well with the experimental and simulated results. [ABSTRACT FROM PUBLISHER]

Propagation of magnetostatic surface waves (MSSW) in yttrium-iron-garnet films deposited by ion-beam evaporation on silicon substrates and consisting of two layers-the buffer layer and the main layer-was studied. It is shown that exchange coupling and surface spin pinning at the interface of the main and buffer layers can enhance nonreciprocity of MSSW propagation and can result in the appearance of anomalous regions in the dispersion curves caused by spin-wave resonances across the film thickness. [ABSTRACT FROM PUBLISHER]

We present the design of readout circuitry based on complementary metal-oxide semiconductors (CMOS) for spin-waves. The circuit provides the functionality of a high-speed oscilloscope/spectrum analyzer, and can be integrated with a spin-wave-based signal processing device. The circuit consumes sub-50 mW power and requires an area below 1 mm2. A spin-wave-based processing system, when combined with the presented electrical input/output circuitry, can perform complex microwave signal processing tasks, with speed, power consumption, and area that are not feasible in a CMOS-only system. [ABSTRACT FROM PUBLISHER]

The propagation of a magnetostatic gap wave in a gap between two ferromagnetic with opposite longitudinal magnetizations is considered under the conditions for relative longitudinal displacement. It is shown that the view of dispersive dependences of a high-frequency and low-frequency modes of magnetostatic gap waves is considerably modified because of displacement of one of a crystals. At the same time the magnetic field of high-frequency mode in the gap displays sensitivity to relative longitudinal displacement of a crystals.

The law of magnetostatic waves dispersion in the manganese and magnesiummanganese ferrospinels films was investigated using the moving-transducer method. The wave numbers, phase and group velocities of magnetostatic waves are defined. The excitation of spin-wave waves in the surface layer of the film is found. The wave numbers, spin pinning options, their frequency dependences and surface anisotropy constants are calculated.

A novel automated design optimization procedure based on the application of an ultrafast computationally efficient finite-element analysis (CE-FEA) for current-regulated synchronous reluctance machines supplied from power electronic converters is proposed. The CE-FEA uses only a minimum number of magnetostatic solutions in order to comprehensively evaluate performance, including ripple torque and core losses. The optimization algorithm is based on differential evolution, and uses as independent variables the torque angle and ratios for a generic rotor topology with four flux barriers. Two problems, one with two and the other with three objectives, are studied and results are compared. Global performance indices and objectives incorporate the effect of average torque output, losses, torque ripple, and power factor at fixed cost. It is shown that through optimal studies with more than 5000 candidate designs, high output power, high efficiency, and low torque ripple can be achieved, while the relatively low power factor remains an inherent limitation of synchronous reluctance technology. Simulations are validated versus tests from a 10-hp 1800-r/min prototype. [ABSTRACT FROM AUTHOR]

Nonreciprocal spin wave propagation, induced by placing a neighboring metallic nonmagnetic layer, has been studied in metallic ferromagnetic thin films. The structure consists of a set of coupled microstrip transmission lines acting as antennas placed over a thin Ni80Fe20 layer. Nonreciprocal propagation of magnetostatic surface waves (MSSWs) has been observed. The nonreciprocal effect is evaluated by the amplitude ratio and the phase difference of the MSSWs traveling in opposite directions. By investigating the correlation between the device structure and the nonreciprocal effects, a maximum of −26.0 dB of the amplitude ratio and −180.0° phase difference were obtained. These results can be applied to optimize the nonreciprocal device. [ABSTRACT FROM PUBLISHER]