arXiv subjects

Mateusz Zelent

Publications and source records attributed to Mateusz Zelent.

15 recordsLinked to original sources

arXiv2026

Spin-wave bandgap engineering via mode hybridization in dipolar-coupled YIG film/CoFeB nanodisk magnonic crystals

We investigate spin-wave transport in hybrid two-dimensional magnonic crystals comprising a low-damping yttrium iron garnet (YIG) film coupled to a periodic array of CoFeB nanodisks. Using propagating spin-wave spectroscopy, super-Nyquist magneto-optical Kerr effect microscopy, and micromagnetic simulations, we demonstrate the formation of pronounced and tunable bandgaps that do not originate from conventional Bragg scattering. Instead, these gaps arise from hybridization between the fundamental magnonic-crystal mode and in-plane transverse standing modes induced by the periodic nanodisk array. The spectral position and width of these gaps are controlled by geometric parameters and by the magnetic state of the nanodisks, including their vortex configuration, which governs both static and dynamic dipolar coupling. For larger lattice periods, additional gaps emerge through hybridization with modes quantized both transverse and parallel to the spin-wave propagation direction, reflecting dispersion folding in two dimensions. Our results establish mode hybridization as a versatile mechanism for engineering spin-wave band structures beyond the constraints of Bragg scattering and provide a pathway toward reconfigurable magnonic devices based on dipolar-coupled hybrid architectures.

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arXiv2025

Hybrid structure with a ferromagnetic film and an array of magnetic molecules for deep-nanoscale reprogrammable magnonics

Miniaturization is an essential element in the development of information processing technologies and is also one of the main determinants of the usability of the tested artificial neural networks. It is also a key element and one of the main challenges in the development of magnonic neuromorphic systems. In this work, we propose a new platform for the development of these new spin-wave-based technologies. Using micromagnetic simulations, we demonstrate that magnetic molecules regularly arranged on the surface of a thin ferromagnetic layer enable resonant coupling of propagating spin waves with the dynamics of the molecules' magnetic moments, opening a gap in the transmission spectrum up to 150 MHz. The gap, its width, and frequency can be controlled by an external magnetic field or the arrangement of molecules on the ferromagnetic surface. Furthermore, the antiferromagnetic arrangement of the magnetic moments of molecules or clusters of molecules allows for control of the gap's position and width. Thus, the proposed hybrid structure offers reprogrammability and miniaturization down to the deep nanoscale, operating frequencies in the range of several GHz, key properties for the implementation of artificial neural networks.

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arXiv2025

Unveiling Micrometer-Range Spin-Wave Transport in Artificial Spin Ice

Artificial spin ice (ASI) systems exhibit fascinating phenomena, such as frustration and the formation of magnetic monopole states, and Dirac strings. However, exploring the wave phenomena in these systems is elusive due to the weak dipolar coupling that governs their interactions. In this study, we demonstrate coherent spin-wave propagation in an hybrid ASI system, which is based on a multilayered ferromagnetic thin film with perpendicular magnetic anisotropy and in-plane magnetized nanoelements embedded within it. We show that this system enables spin-wave transmission over a one-micrometer distance via exchange-mediated coupling between subsystems and evanescent spin-wave tunneling through the out-of-plane magnetized parts. This system overcomes the limitations of purely dipolar interactions in standard ASIs while preserving their fundamental properties. Thus, it provides a platform for studying spin-wave phenomena in frustrated ASI systems and paves the way for exploiting them in analog signal processing with spin waves.

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arXiv2025

Efficient Generation of Second-Harmonic Propagating Spin Waves in a Thin, Out-of-Plane-Magnetized Ferromagnetic Film

Spin waves are attractive information carriers owing to their gigahertz-to-terahertz frequencies, nanometric wavelengths, and negligible Joule heating. Yet the efficient excitation of short-wavelength, high-frequency spin waves and the exploitation of nonlinear effects remain challenging. We propose a hybrid ferromagnetic nanostructure composed of a small, in-plane-magnetized rim (a magnonic nanocavity) exchange-coupled to an out-of-plane-magnetized region. Micromagnetic simulations show that a spatially uniform out-of-plane microwave field excites the rim's fundamental mode; its second harmonic is then coherently and efficiently launched into the second region of the structure, yielding propagating spin waves. The process can be realized in strip or disk geometries, providing excitation of plane-wave or radial spin waves, respectively. The conversion efficiency grows nonlinearly with the pump amplitude and can be further improved when the frequency of a higher-order standing wave in the nanocavity matches the second-harmonic frequency. The emission frequency is tunable via the bias magnetic field or the width of the nanocavity, suggesting a compact route toward on-chip, short-wavelength, high-frequency spin-wave sources for artificial neural networks.

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arXiv2025

Stabilization of the skyrmion in a hybrid magnetic-superconducting nanostucture

Stabilization of skyrmions in a magnetic material without the Dzyaloshinskii-Moriya exchange interaction requires using of an inhomogeneous magnetic field, such as a demagnetization field or an Oersted field. To control and tune the local magnetic field in magnetic material we propose to exploit superconducting nanorings. The field stabilizes the skyrmion through the presence of persistent current induced by the pulses of external field. We analyze the conditions for the stabilization of Neel skyrmion in ferromagnetic layers with out-of-plane anisotropy, as a function of the nanoring size and induced superconducting current. We show that the superconducting current should exceed a critical value for the skyrmion to become stable. The paper presents consistent results from both analytical and micromagnetic calculations for Co and Ga:YIG thin magnetic films.

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arXiv2025

Beyond fixed-size skyrmions in nanodots: switchable multistability with ferromagnetic ring

We demonstrate a novel approach to control and stabilize magnetic skyrmions in ultrathin multilayer nanostructures through spatially engineered magnetostatic fields generated by ferromagnetic nanorings. Using analytical modeling and micromagnetic simulations, we show that the stray fields from a Co/Pd ferromagnetic ring with out-of-plane magnetic anisotropy significantly enhance Néel-type skyrmion stability in an Ir/Co/Pt nanodot, even without Dzyaloshinskii-Moriya interaction. Most notably, we observe a multistability phenomenon, where skyrmions can be stabilized at two or more distinct equilibrium diameters depending on the ring's magnetization orientation. These stable states exhibit energy barriers substantially exceeding thermal fluctuations at room temperature, suggesting practical applications for robust multibit memory storage. By tuning geometric parameters of the ferromagnetic ring, we demonstrate precise control over skyrmion size and stability, opening pathways for advanced spintronic nanodevices.

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arXiv2025

Angle-dependent resonant dynamics of stripes and skyrmions in Re/Co/Pt multilayers

The dynamic behavior and stabilization of skyrmions in magnetic multilayers are critical for advancing spintronic and magnonic technologies. In our study, we investigate the static and dynamic properties of $[Re/Co(d_{Co})/Pt]_{20}$ multilayers with varying Co thicknesses $(6\text{-}24 \, \text{Å})$, showcasing a transition from out-of-plane to in-plane magnetic anisotropy. Magnetization reversal leads to a transformation from labyrinth domains to skyrmion bubbles due to the interfacial Dzyaloshinskii-Moriya interaction (iDMI). Using angle-dependent imaging at remanence, we confirm that skyrmions can be stabilized without an external magnetic field at specific polar angles, with the stabilization angle increasing alongside Co thickness. Ferromagnetic resonance spectroscopy reveals four distinct resonant modes, including low-frequency $(2\text{-}18\text{GHz})$, high-frequency $(20\text{-}35 \, \text{GHz})$ modes, depending on the magnetization texture. The frequency range of these modes narrows with decreasing effective anisotropy and iDMI strength decreases in thicker Co layers in perpendicular configurations. Moreover, we observe a decrease in effective Gilbert damping with increasing Co thickness, highlighting the potential for efficient energy dissipation. These findings link between material properties and skyrmion dynamics directly and demonstrate tunable resonant modes for magnonic devices. By addressing both static and dynamic aspects, our work advances the development of next-generation spintronic and magnonic applications.

cond-mat.mtrl-sci↗

arXiv2024

Enhancement of dynamical coupling in artificial spin-ice systems by incorporating perpendicularly magnetized ferromagnetic matrix

Artificial spin-ice systems, consisting of arrays of interacting ferromagnetic nanoelements, offer a versatile platform for reconfigurable magnonics with potential in GHz logic and neuromorphic computing. However, weak dipolar coupling between nanoelements severely limits their functionality. We numerically demonstrate a rich spin-wave spectrum in a square spin-ice structure immersed in a perpendicularly magnetized ferromagnetic matrix, which is different from a single spin-ice system. We observe a strong magnon-magnon coupling between the bulk second-order mode of the nanoelements and the fundamental mode of the matrix, supported by a pronounced anticrossing frequency gap. We show that, in addition to the dipolar coupling, exchange interactions at the nanoelement-matrix interface play a crucial role in this hybridization. Furthermore, the strength of the coupling can be enhanced by almost 40% just by reconfiguring the magnetization at the vertices from low-energy to high-energy monopole states. These results open the way to exploit artificial spin-ice systems for magnonic applications, taking advantage of the strong coupling and vertex-dependent dynamics.

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arXiv2024

Reconfigurable spin-wave platform based on interplay between nanodots and waveguide in hybrid magnonic crystal

We present a hybrid magnonic crystal composed of a chain of nanodots with strong perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction, positioned above a permalloy waveguide. The micromagnetic study examines two different magnetization states in the nanodots: a single-domain state and an egg-shaped skyrmion state. Due to the dipolar coupling between the dot and the waveguide, a strongly bound hybrid magnetization texture is formed in the system. Our results show complex spin-wave spectra, combining the effects of periodicity, magnetization texture, and hybridization of the propagating waves in the waveguide with the dot/skyrmion modes. The dynamics of the systems are characterized by several key features which include differences in band-gap sizes, the presence of flat bands in the skyrmion state that can form both bound and hybridized states, the latter sometimes leading to the presence of additional non-Bragg band gaps, and a broad frequency range of only waveguide-dominated modes in the single-domain state. Thus, the study shows that the proposed hybrid magnonic crystals have many distinct functionalities, highlighting their reconfigurable potential, magnon-magnon couplings, mode localization, and bound states overlapping with the propagating waves. This opens up potential applications in analog and quantum magnonics, spin-wave filtering, and the establishment of magnonic neural networks.

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arXiv2024

Exploration of magnon-magnon coupling in an antidot lattice: The role of non-uniform magnetization texture

We numerically study the spin wave dynamics in an antidot lattice based on a Co/Pd multilayer structure with reduced perpendicular magnetic anisotropy at the edges of the antidots. This structure forms a magnonic crystal with a periodic antidot pattern and a periodic magnetization configuration consisting of out-of-plane magnetized bulk and in-plane magnetized rims. Our results show the different behavior of spin waves in the bulk and in the rims under varying out-of-plane external magnetic field strength, revealing complex spin-wave spectra and hybridizations between the modes of these two subsystems. A particularly strong magnon-magnon coupling, due to exchange interactions, is found between the fundamental bulk spin-wave mode and the second-order radial rim modes. However, the dynamical coupling between the spin-wave modes at low frequencies, involving the first-order radial rim modes, is masked by the changes in the static magnetization at the bulk-rim interface with magnetic field changes. The study expands the horizons of magnonic-crystal research by combining periodic structural patterning and non-collinear magnetization texture to achieve strong magnon-magnon coupling, highlighting the significant role of exchange interactions in the coupling.

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arXiv2023

Control of vortex chirality in a symmetric ferromagnetic ring using ferromagnetic nanoelement

Controlling the vortex chirality in ferromagnetic nanodots and nanorings has been a topic of investigation for the last few years. Many control methods have been proposed and it has been found that the control is related to the breaking of the circular symmetry. In this paper, we present a theoretical study demonstrating the control of chirality in ferromagnetic nanoring without directly breaking its symmetry, but instead by placing elongated ferromagnetic nanoelement inside the ring, Here, the stray magnetostatic field exerted by the asymmetrically placed nanoelement determines the movement of the domain walls upon remagnetization of the nanoring and the resulting chirality in the remanence. This approach allows the chirality of the vortex state to be controlled and also promises its control in a dense array of nanorings, thus suitable for spintronic and magnonic applications.

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arXiv2022

Spin Dynamics in Patterned Magnetic Multilayers with Perpendicular Magnetic Anisotropy

The magnetization dynamics in nanostructures has been extensively studied in the last decades, and nanomagnetism has evolved significantly over that time, discovering new effects, developing numerous applications, and identifying promising new directions. This includes magnonics, an emerging research field oriented on the study of spin-wave dynamics and their applications. In this context, thin ferromagnetic films with perpendicular magnetic anisotropy (PMA) offer interesting opportunities to study spin waves, in particular, due to out-of-plane magnetization in remanence or at relatively weak external magnetic fields. This is the only magnetization configuration offering isotropic in-plane spin-wave propagation within the sample plane, the forward volume magnetostatic spin-wave geometry. The isotropic dispersion relation is highly important in designing signal-processing devices, offering superior prospects for direct replicating various concepts from photonics into magnonics. Analogous to photonic or phononic crystals, which are the building blocks of optoelectronics and phononics, magnonic crystals are considered as key components in magnonics applications. Arrays of nanodots and structured ferromagnetic thin films with a periodic array of holes, popularly known as antidot lattices based on PMA multilayers have been recently studied. Novel magnonic properties related to propagating spin-wave modes, exploitation of the band gaps, and confined modes, were demonstrated. Also, the existence of nontrivial magnonic band topologies has been shown. Moreover, the combination of PMA and Dzyaloshinskii-Moriya interaction leads to the formation of chiral magnetization states, including Néel domain walls, skyrmions, and skyrmionium states.

cond-mat.mtrl-sci↗

arXiv2022

Stabilization and application of asymmetric Néel skyrmions in hybrid nanostructures

Increasing amounts of information force the continuous improvement of information storage and processing technologies, further device miniaturization, and their efficiency increase. Magnetic skyrmions, topological quasiparticles, and the smallest stable magnetic textures possess intriguing properties and potential for data storage applications. Hybrid nanostructures with elements of different magnetization orientations can offer additional advantages for developing skyrmion-based spintronic and magnonic devices. We show that an Néel-type skyrmion confined within a nanodot placed on top of a ferromagnetic stripe produces a unique and compelling platform for exploring mutual coupling between magnetization textures. The skyrmion induces an imprint upon the stripe, which, in turn, asymmetrically squeezes the skyrmion in the dot, increasing their size and the range of skyrmion stability for small values of DMI, as well as introducing skyrmion bi-stability. At the end, we present a proof-of-concept technique for unconstrained transport of a skyrmion along a racetrack based on proposed hybrid systems. Our results demonstrate a hybrid structure that is promising for applications in magnonics and spintronics.

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arXiv2019

Magnons in a Quasicrystal: Propagation, Localization and Extinction of Spin Waves in Fibonacci Structures

Magnonic quasicrystals exceed the possibilities of spin wave (SW) manipulation offered by regular magnonic crystals, because of their more complex SW spectra with fractal characteristics. Here, we report the direct x-ray microscopic observation of propagating SWs in a magnonic quasicrystal, consisting of dipolarly coupled permalloy nanowires arranged in a one-dimensional Fibonacci sequence. SWs from the first and second band as well as evanescent waves from the band gap between them are imaged. Moreover, additional mini-band gaps in the spectrum are demonstrated, directly indicating an influence of the quasiperiodicity of the system. The experimental results are interpreted using numerical calculations and we deduce a simple model to estimate the frequency position of the magnonic gaps in quasiperiodic structures. The demonstrated features of SW spectra in one-dimensional magnonic quasicrystals allows utilizing this class of metamaterials for magnonics and makes them an ideal basis for future applications.

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arXiv2017

Co- and contra-directional vertical coupling between ferromagnetic layers with grating for short-wavelength spin wave generation

The possibility to generate short spin waves is of great interest in the field of magnonics nowadays. We present an effective and technically affordable way of conversion of long spin waves, which may be generated by conventional microwave antenna, to the short, sub-micrometer waves. It is achieved by grating-assisted resonant dynamic dipolar interaction between two ferromagnetic layers separated by some distance. We analyze criteria for the optimal conversion giving a semi-analytical approach for the coupling coefficient. We show by the numerical calculations the efficient energy transfer between layers which may be either of co-directional or contra-directional type. Such a system may operate either as a short spin wave generator or a frequency filter, moving foreward possible application of magnonics.

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