Vladislav A. Gubanov

The results of the study of spin waves in an irregular structure controlled both by the orientation of the external magnetic field and by the application of laser heating to the rounding region of the irregular U-shaped structure are presented. It is shown that the considered wave-guiding structure can be used as a logic element of the ‘key’ type.

The paper presents the results of micromagnetic modeling based on the numerical solution of the Landau–Lifshitz–Gilbert equation for a system of laterally coupled microwave guides made of yttrium iron garnet film. The possibility of controlling the characteristics of spin wave propagation in the structure by changing the air gap between the microwave guides is studied. It is shown that the proposed system allows for the effective redistribution of spin wave power in the output sections of the structure, which opens up possibilities for use in magnonics devices, in particular, for creating directional spin wave couplers used in processing information signals.

Results are presented from micromagnetic modeling of the magnetic structure on the surface of a yttrium iron garnet film with a region of altered saturatio

We report on the spin-wave propagation along a magnonic waveguide with a local area of decreased magnetization, which is induced by heating produced with a focused laser spot. A phase-sensitive Brillouin light scattering technique is used to image how the spin wave propagates along the waveguide with a local heat landscape. Frequency-selective signal propagation along the waveguide is demonstrated. Micromagnetic simulations reveal intermodal interference variation in the region after the heated area. The proposed way to reconfigure the magnetization landscape can be used in magnonic devices with frequency-selective spin-wave transport.

Purpose of this study is to elucidate the mechanism of transformation of electromagnetic and exchange spin waves (ESW) in a thin transition layer of epitaxial ferrite–dielectric structures, as well as to investigate the possibilities of using short-wave ESW to diagnose magnetic inhomogeneities of epitaxial yttrium-iron garnet (YIG) films. Methods. In this paper, we study the hybridization processes of electromagnetic and exchange spin waves that occur in the transition layer of the YIG film. The features of the dispersion of coupled waves in the vicinity of phase synchronism frequencies under normal and tangential magnetization of the YIG film are investigated. Results. It is shown that within of the thickness transition layer, the dispersion of the excited ESW experiences significant distortions, which manifests itself in frequency shifts of the spin-wave resonance. Based on this, a method for calculating the distribution of spontaneous magnetization over the thickness of the YIG film was proposed, which was used to simulate the processes of excitation of spin-wave resonances. Conclusion. The proposed technique of spin-wave diagnostics of YIG films can be effectively used for non-destructive testing of all types of epitaxial ferrite-dielectric structures, which may be in demand in the field of production and in the field of their practical application.

Бистабильность магнитных скирмионов в многослойной структуре ферромагнетик/тяжелый металл

We demonstrated numerically the skyrmion formation in ultrathin nanodisks using a magnetic force microscopy tip. We found that the local magnetic field generated by the magnetic tip significantly affects the magnetization state of the nanodisks and leads to the formation of skyrmions. Experimentally, we confirmed the influence of the local field on the magnetization states of the disks. Micromagnetic simulations explain the evolution of the magnetic state during magnetic force microscopy scanning and confirm the possibility of skyrmion formation. The formation of the horseshoe magnetic domain is a key transition from random labyrinth domain states into the skyrmion state. We showed that the formation of skyrmions by the magnetic probe is a reliable and repetitive procedure. Our findings provide a simple solution for skyrmion formation in nanodisks.

Regimes of controlling dipole coupling in a lateral system of nonidentical magnonic crystals have been studied by the Brillouin light scattering and micromagnetic simulation methods. Regimes of spatial and frequency selection of a spin-wave signal near the frequency of the non-transmission band edge of a magnonic crystal are revealed. The influence of a change in the geometric parameters on the properties of waveguide modes near the Bragg resonance frequency are investigated. The obtained results can be used for designing microwave-signal processing devices, such as demultiplexers, power dividers, and couplers.

Understanding the stability of magnetic textures in multilayer patterned dots would constitute a significant step toward skyrmion-based applications. Here, we report the observation of skyrmions in patterned nanodots composed of multilayers. We examine the stabilization of various magnetic states such as single-domain states, skyrmion states, horseshoe-like domain structures, and worm-like domain structures in submicrometer dots (diameters 150–525 nm). Dots are fabricated from Pt/Co/Au multilayer structures that exhibit the interfacial Dzyaloshinskii–Moriya interaction and perpendicular magnetic anisotropy. In particular, we show that a stack of six repetitions of Pt/Co/Au layers suffices to stabilize the skyrmion state inside a dot at room temperature. A micromagnetic simulation determines the regime of skyrmion stability. The results reveal a correlation between the magnetic-force microscopy measurements and the micromagnetic simulation. Furthermore, we explain the development of the magnetic state with increasing dot diameter. We envision that nanopatterning of multilayer magnetic films could serve as a versatile way of creating magnetic skyrmion states.

Using Brillouin light spectroscopy and micromagnetic simulation methods, we show how the intermodal coupling between two magnonic crystals (MCs) affects signals spatial selection with frequency separation during spin-wave transport. We have experimentally demonstrated control of the intermodal coupling of spin waves (SWs) propagating in non-identical magnonic-crystal microwaveguides near the band gap frequency. We show that the spin-wave propagation direction within the MCs of different width can be controlled by the lateral coupling between SWs. Our findings provide an alternative method for signal filtering and separation within magnonic networks for the implementation of magnonic demultiplexers, power dividers, couplers and microwave signal processing devices. based on the lateral array of non-identical MCs.