arXiv subjects

P. Gruszecki

Publications and source records attributed to P. Gruszecki.

14 recordsLinked to original sources

arXiv2022

Spin-wave Talbot effect in thin ferromagnetic film

The Talbot effect has been known in optics since XIX century and found various technological applications. In this paper, we demonstrate with the help of micromagnetic simulations this self-imaging phenomenon for spin waves propagating in a thin ferromagnetic film magnetized out-of-plane. We show that the main features of the obtained Talbot carpets for spin waves can be described, to a large extent, by the approximate analytical formulas yielded by the general analysis of the wave phenomena. Our results indicate a route to a feasible experimental realisation of the Talbot effect at low and high frequencies and offer interesting effects and possible applications in magnonics.

cond-mat.mes-hall↗

arXiv2022

Magnetization statics and dynamics in (Ir/Co/Pt)$_6$ multilayers with Dzyaloshinskii-Moriya interaction

Magnetic multilayers of (Ir/Co/Pt)$_6$ with interfacial Dzyaloshinskii-Moriya interaction (IDMI) were deposited by magnetron sputtering with Co thickness $d=1.8$ nm. Exploiting magneto-optical Kerr effect in longitudinal mode microscopy, magnetic force microscopy, and vibrating sample magnetometry, the magnetic field-driven evolution of domain structures and magnetization hysteresis loops have been studied. The existence of weak stripe domains structure was deduced -- tens micrometers size domains with in-plane "core" magnetization modulated by hundred of nanometers domains with out-of-plane magnetization. Micromagnetic simulations interpreted such magnetization distribution. Quantitative evaluation of IDMI was carried out using Brillouin light scattering (BLS) spectroscopy as the difference between Stokes and anti-Stokes peak frequencies $Δf$. Due to the additive nature of IDMI, the asymmetric combination of Ir and Pt covers led to large values of effective IDMI energy density $D_\mathrm{eff}$. It was found that Stokes and anti-Stokes frequencies as well as $Δf$, measured as a function of in-plane applied magnetic field, show hysteresis. These results are explained under the consideration of the influence of IDMI on the dynamics of the in-plane magnetized "core" with weak stripe domains.

cond-mat.mes-hall↗

arXiv2021

Roadmap on Spin-Wave Computing

Magnonics is a field of science that addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operations in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of the current challenges and the outlook of the further development of the research directions.

physics.app-ph↗

arXiv2020

Spin-wave spectroscopy of individual ferromagnetic nanodisks

The increasing demand for ultrahigh data storage densities requires development of 3D magnetic nanostructures. In this regard, focused electron beam induced deposition (FEBID) is a technique of choice for direct-writing of various complex nano-architectures. However, intrinsic properties of nanomagnets are often poorly known and can hardly be assessed by local optical probe techniques. Here, we demonstrate spatially resolved spin-wave spectroscopy of individual circular magnetic elements with radii down to 100 nm. The key component of the setup is a microwave antenna whose microsized central part is placed over a movable substrate with well-separated CoFe-FEBID nanodisks. The circular symmetry of the disks gives rise to standing spin-wave resonances and allows for the deduction of the saturation magnetization and the exchange stiffness of the material using an analytical theory. The presented approach is especially valuable for the characterization of direct-write elements opening new horizons for 3D nanomagnetism and magnonics.

cond-mat.mes-hall↗

arXiv2020

An anomalous refraction of spin waves as a way to guide signals in curved magnonic multimode waveguides

We present a method for efficient spin wave guiding within the magnonic nanostructures. Our technique is based on the anomalous refraction in the metamaterial flat slab. The gradual change of the material parameters (saturation magnetization or magnetic anisotropy) across the slab allows tilting the wavefronts of the transmitted spin waves and controlling the refraction. Numerical studies of the spin wave refraction are preceded by the analytical calculations of the phase shift acquired by the spin wave due to the change of material parameters in a confined area. We demonstrate that our findings can be used to guide the spin waves smoothly in curved waveguides, even through sharp bends, without reflection and scattering between different waveguide's modes, preserving the phase -- the quantity essential for wave computing.

physics.app-ph↗

arXiv2019

Goos-Hanchen Shift of a Spin-Wave Beam at the Interface Between Two Ferromagnets

Spin waves are promising information carriers which can be used in modern magnonic devices, characterized by higher performance and lower energy consumption than presently used electronic circuits. However, before practical application of spin waves, the efficient control over spin wave amplitude and phase needs to be developed. We analyze analytically reflection and refraction of the spin waves at the interface between two ferromagnetic materials. In the model we consider the system consisting of two semi-infinite ferromagnetic media, separated by the ultra-narrow interface region with the magnetic anisotropy. We have found the Goos-Hanchen shift for spin waves in transmission and reflection, and performed detailed investigations of its dependence on the anisotropy at the interface and materials surrounding the interface. We have demonstrated possibility of obtaining Goos-Hanchen shift of several wavelengths in reflection for realistic material parameters. That proves the possibility for change of the spin waves phase in ferromagnetic materials at subwavelength distances, which can be regarded as a metasurface for magnonics.

cond-mat.mes-hall↗

arXiv2019

Ultra-narrow spin wave metasurface for focusing application

In this paper we show that the phase shift of the spin waves can be controlled in transmission through metasurface represented as an ultra-narrow non-magnetic spacer separating two ferromagnetic films. We design this metasurface to present the focusing of spin waves in an Co thin film. For this purpose we exploit the strength of the interlayer exchange coupling interactions of RKKY type which allows to control the phase of the transmitted and reflected spin waves in the wide range of angles [$-π/2$;$π/2$]. We combined this phase-shift dependency with the lens equation to demonstrate numerically the lens for spin waves based on ultra-narrow metasurface.

physics.app-ph↗

arXiv2017

Azimuthal Spin Wave Excitations in Magnetic Nanodots over the Soliton Background: Vortex, Bloch and Néel-like skyrmions

We study azimuthal spin-wave (SW) excitations in a circular ferromagnetic nanodot in different inhomogeneous, topologically non-trivial magnetization states, specifically, vortex, Bloch-type skyrmion and Néel-type skyrmion states. Continuous mapping of the SW spectrum between these states is realized with gradual change of the out-of-plane magnetic anisotropy and Dzyaloshinskii-Moriya exchange interaction (DMI). Our study shows lifting of the SW frequencies degeneracy and change in systematics of the frequency levels. The change is induced by a geometrical Berry phase, that is present for the dot-edge localized SWs in a vortex state and vanishes in skyrmion states. Furthermore, channeling of the azimuthal SWs localized at the skyrmion edge is present and induces large frequency splitting. This is attributed to DMI induced nonreciprocity, while coupling of the breathing and gyrotropic modes is related to soliton motion. Finally, an efficient coupling of the dynamic magnetization in the skyrmion state to uniform magnetic field in nanodots with non-circular symmetry is shown.

cond-mat.mes-hall↗

arXiv2017

Magnonic crystals - prospective structures for shaping spin waves in nanoscale

We have investigated theoretically band structure of spin waves in magnonic crystals with periodicity in one-(1D), two- (2D) and three-dimensions (3D). We have solved Landau-Lifshitz equation with the use of plane wave method, finite element method in frequency domain and micromagnetic simulations in time domain to find the dynamics of spin waves and spectrum of their eigenmodes. The spin wave spectra were calculated in linear approximation. In this paper we show usefulness of these methods in calculations of various types of spin waves. We demonstrate the surface character of the Damon-Eshbach spin wave in 1D magnonic crystals and change of its surface localization with the band number and wavenumber in the first Brillouin zone. The surface property of the spin wave excitation is further exploited by covering plate of the magnonic crystal with conductor. The band structure in 2D magnonic crystals is complex due to additional spatial inhomogeneity introduced by the demagnetizing field. This modifies spin wave dispersion, makes the band structure of magnonic crystals strongly dependent on shape of the inclusions and type of the lattice. The inhomogeneity of the internal magnetic field becomes unimportant for magnonic crystals with small lattice constant, where exchange interactions dominate. For 3D magnonic crystals, characterized by small lattice constant, wide magnonic band gap is found. We show that the spatial distribution of different materials in magnonic crystals can be explored for tailored effective damping of spin waves.

cond-mat.mes-hall↗

arXiv2017

Spin-wave dynamics in Permalloy/Cobalt magnonic crystals in the presence of a non-magnetic spacer

In this paper, we theoretically study the influence of a non-magnetic spacer between ferromagnetic dots and ferromagnetic matrix on the frequency dispersion of the spin wave excitations in two-dimensional bi-component magnonic crystals. By means of the dynamical matrix method we investigate structures inhomogeneous across the thickness represented by square arrays of Cobalt or Permalloy dots in a Permalloy matrix. We show that the introduction of a non-magnetic spacer significantly modifies the total internal magnetic field especially at the edges of the grooves and dots. This permits the manipulation of the magnonic band structure of spin waves localized either at the edges of the dots or in matrix material at the edges of grooves. According to the micromagnetic simulations two types of end modes were found. The corresponding frequencies are significantly influenced by the end modes localization region. We also show that, with the use of a single ferromagnetic material, it is possible to design a magnonic crystal preserving properties of bi-component magnonic crystals and magnonic antidot lattices. Finally, the influence of the non-magnetic spacers on the technologically relevant parameters like group velocity and magnonic band width are discussed.

cond-mat.mes-hall↗

arXiv2016

Goos-Hanchen shift of a spin-wave beam transmitted through anisotropic interface between two ferromagnets

The main object of investigation in magnonics, spin waves (SWs) are promising information carriers. Presently the most commonly studied are plane wave-like SWs and SWs propagating in confined structures, such as waveguides. Here we consider a Gaussian SW beam obliquely incident on an ultra-narrow interface between two identical ferromagnetic materials. We use an analytical model and micromagnetic simulations for an in-depth analysis of the influence of the interface properties, in particular the magnetic anisotropy, on the transmission of the SW beam. We derive analytical formulas for the reflectance, transmittance, phase shift and Goos-Hanchen (GH) shift for beams reflected and refracted by an interface between two semi-infinite ferromagnetic media; the results for the refracted beam are the first to be reported to date. The GH shifts in SW beam reflection and transmission are confirmed by micromagnetic simulations in the thin-film geometry. We demonstrate the dependence of the characteristic properties on the magnetic anisotropy at the interface, the angle of incidence and the frequency of the SWs. We also propose a method for the excitation of high-quality SW beams in micromagnetic simulations.

cond-mat.mes-hall↗

arXiv2015

Microwave excitation of spin wave beams in thin ferromagnetic films

We present an approach enabling generation of narrow spin wave beams in thin homogeneous ferromagnetic films. The main idea is to match the wave vector of the spin wave with that corresponding to the spectral maximum of the exciting microwave magnetic field only locally, in the region of space from which the beam should be launched. We show that this can be achieved with the aid of a properly designed coplanar waveguide transducer generating a nonuniform microwave magnetic field. The resulting two-dimensional spin wave beams obtained in micromagnetic simulations propagate over distances of several micrometers. The proposed approach requires neither inhomogeneity of the ferromagnetic film nor nonuniformity of the biasing magnetic field, and it can be generalized to yield multiple spin wave beams of different width at the same frequency. Other possible excitation scenarios and applications of spin wave beam magnonics are also discussed.

cond-mat.mes-hall↗

arXiv2015

Influence of magnetic surface anisotropy on spin wave reflection from the edge of ferromagnetic film

We study propagation of the Gaussian beam of spin waves and its reflection from the edge of thin yttrium-iron-garnet film with in-plane magnetization perpendicular to this edge. We have performed micromagnetic simulations supported by analytical calculations to investigate influence of the surface magnetic anisotropy present at the film edge on the reflection, especially in the context of the Goos-Hanchen effect. We have shown the appearance of a negative lateral shift between reflected and incident spin wave beams' spots. This shift is particularly sensitive to the surface magnetic anisotropy value and is a result of the Goos-Hanchen shift which is sensitive to the magnitude of the anisotropy and of the bending of spin wave beam. We have demonstrated that the demagnetizing field provide graded increase of the refractive index for spin waves, which is responsible for the bending.

cond-mat.mes-hall↗

arXiv2015

Collective dynamical skyrmions excitations in magnonic crystal

We investigate theoretically skyrmion magnonic crystal, i.e., the dynamics of the magnetization in a chain of the ferromagnetic nanodots being in skyrmion magnetic configuration. We show that collective excitations are possible to be observed in the structure. We present the dispersion relation of the coupled skyrmions. It exhibit a periodical property in dependence on wave vector, characteristic feature of the band structure in magnonic crystals. Spatial analysis of the magnetization amplitude associated with the magnonic bands confirms type of the excited modes, as breathing and clockwise gyrotropic dynamical skyrmions. These high and low frequency excitations, propagate with negative and positive group velocity, respectively, and can be explored for study fundamental properties and technological applications in spintronics and magnonics.

cond-mat.mes-hall↗