S. V. Grishin

Magnonic beam splitter: The building block of parallel magnonic circuitry

We demonstrate a magnonic beam splitter that works by inter-converting magnetostatic surface and backward-volume spin waves propagating in orthogonal sections of a T-shaped yttrium iron garnet structure. The inter-conversion is enabled by the overlap of the surface and volume spin wave bands. This overlap results from the demagnetising field induced along the transversely magnetised section(-s) of the structure and the quantization of the transverse wave number of the propagating spin waves (which are therefore better described as waveguide modes). In agreement with numerical micromagnetic simulations, our Brillouin light scattering imaging experiments reveal that, depending on the frequency, the incident fundamental waveguide magnonic modes may also be converted into higher order waveguide modes. The magnonic beam splitter demonstrated here is an important step towards the development of parallel logic circuitry of magnonics.

Nonlinear spin wave coupling in adjacent magnonic crystals

We have experimentally studied the coupling of spin waves in the adjacent magnonic crystals. Space- and time-resolved Brillouin light-scattering spectroscopy is used to demonstrate the frequency and intensity dependent spin-wave energy exchange between the side-coupled magnonic crystals. The experiments and the numerical simulation of spin wave propagation in the coupled periodic structures show that the nonlinear phase shift of spin wave in the adjacent magnonic crystals leads to the nonlinear switching regime at the frequencies near the forbidden magnonic gap. The proposed side-coupled magnonic crystals represent a significant advance towards the all-magnonic signal processing in the integrated magnonic circuits.

Self-generation of dissipative solitons in magnonic quasicrystal active ring resonator

Self-generation of dissipative solitons in the magnonic quasicrystal (MQC) active ring resonator is studied theoretically and experimentally. The developed magnonic crystal has quasiperiodic Fibonacci type structure. Frequency selectivity of the MQC together with the parametric three-wave decay of magnetostatic surface spin wave (MSSW) leads to the dissipative soliton self-generation. The transfer matrix method is used to describe MQC transmission responses. Besides, the model of MQC active ring resonator is suggested. The model includes three coupled differential equations describing the parametric decay of MSSW and two differential equations of linear oscillators describing the frequency selectivity of MQC. Numerical simulation results of dissipative soliton self-generation are in a fair agreement with experimental data.

Self-Generation of Chaotic Dissipative Soliton Trains in Active Ring Resonator With 1-D Magnonic Crystal

Self-generation of chaotic dissipative soliton trains was observed in an active ring resonator based on 1-D periodical ferromagnetic structure (1-D magnonic crystal) in a grooves grating form. The grooves were cut off on the surface of yttrium iron garnet film with the help of a scribing technique and placed perpendicularly to the magnetostatic surface wave (MSSW) propagation. The presence of three magnon decay processes of MSSW, a frequency filtration, and a passive synchronization of the spin-wave self-modulation frequencies caused the self-generation of chaotic dissipative soliton trains. Passive synchronization was realized at frequencies of the first band gap because of the presence of a saturable absorption of a microwave signal.

Dissipative soliton generation in an active ring resonator based on magnonic quasicrystal with Fibonacci type structure

This study reports on the experimental investigations of a magnetostatic surface wave (MSSW) propagation in a magnonic quasicrystal (MQC) with Fibonacci type structure. It is shown that such structure has a greater number of band gaps and narrower pass bands located between them than a periodic structure. These features of the MQC and three-wave decay of the MSSW are used in a MQC active ring resonator for the eigenmode selection and dissipative soliton self-generation.

Generation of propagating spin waves from regions of increased dynamic demagnetising field near magnetic antidots

We have used Brillouin Light Scattering and micromagnetic simulations to demonstrate a point-like source of spin waves created by the inherently nonuniform internal magnetic field in the vicinity of an isolated antidot formed in a continuous film of yttrium-iron-garnet. The field nonuniformity ensures that only well-defined regions near the antidot respond in resonance to a continuous excitation of the entire sample with a harmonic microwave field. The resonantly excited parts of the sample then served as reconfigurable sources of spin waves propagating (across the considered sample) in the form of caustic beams. Our findings are relevant to further development of magnonic circuits, in which point-like spin wave stimuli could be required, and as a building block for interpretation of spin wave behavior in magnonic crystals formed by antidot arrays.

Field-Controlled Phase-Rectified Magnonic Multiplexer

The mechanism used to alter the features of propagating spin waves is a key component underpinning the functionality of high-frequency magnonic devices. Here, using experiment and micromagnetic simulations, we demonstrate the feasibility of a magnonic multiplexer in which the spin-wave beam is toggled between device output branches by the polarity of a small global bias magnetic field. Due to the anisotropy inherent in the dispersion of magnetostatic spin waves, the phase fronts of the output spin waves are asymmetrically tilted relative to the direction of the beam propagation (group velocity). We show how the phase tilts could be (partly) rectified in the magnonic waveguides of variable widths.

Magnonic Bandgap Control in Coupled Magnonic Crystals

The periodic structure in the form of two coupled magnonic crystals (MCs) was considered for the first time. It was shown that the variation of coupling allows to control effectively the characteristics of the bandgaps in the spectrum of magnetostatic spin waves. Main features of formation of the bandgaps were investigated in the basis of theoretical and experimental results. The comparison with a periodic structure in the form of a single MC was provided. The possibility of formation of two frequency bandgaps and shift of the frequency bandgaps depending on coupling was demonstrated in the frequency region of the first Bragg resonance. It was shown that the control of bandgaps in such structure gives additional opportunities to create microwave filters and phase shifters with desired characteristics.

Generation of a stationary train of chaotic soliton-like microwave pulses in self-oscillating ring systems with a ferromagnetic thin film

The generation of a stationary train of chaotic soliton-like microwave pulses has been observed in an isolated self-oscillating ring system with a ferromagnetic thin-film and a resonator. The pulses have been formed owing to three-wave parametric processes and modulation instability of a surface magnetostatic wave. The soliton-like character of the microwave pulses is indicated by the time dependence of the instantaneous phase of the signal envelope.

Brillouin light scattering study of transverse mode coupling in confined yttrium iron garnet/barium strontium titanate multiferroic

Using the space-resolved Brillouin light scattering spectroscopy we study the transformation of dynamic magnetization patterns in a bilayer multiferroic structure. We show that in the comparison with a single yttrium iron garnet (YIG) film magnetization distribution is transformed in the bilayer structure due to the coupling of waves propagating both in an YIG film (magnetic layer) and in a barium strontium titanate slab (ferroelectric layer). We present a simple electrodynamic model using the numerical finite element method to show the transformation of eigenmode spectrum of confined multiferroic. In particular, we demonstrate that the control over the dynamic magnetization and the transformation of spatial profiles of transverse modes in magnetic film of the bilayer structure can be performed by the tuning of the wavevectors of transverse modes. The studied confined multiferroic stripe can be utilized for fabrication of integrated dual tunable functional devices for magnonic applications.