A. B. Khutieva

Diffraction of a surface spin wave by a through hole formed inside the in-plane magnetized yttrium iron garnet (YIG) film is investigated both experimentally and theoretically for the case where the hole diameter is significantly smaller than the wavelength. The study reveals a super-resolution and super-directional propagation phenomenon characterized by the formation of a distinct shadow trace from the hole in the spin-wave profile. This shadow is elongated at a long distance from the hole. This occurs along the directions of super-directional wave propagation, corresponding to the inflection points of the isofrequency curve. Theoretical predictions show excellent agreement with experimental observations of super-directional magnon beams engineered by anisotropic dispersion in YIG and are further validated by micromagnetic simulations. The observed formation and splitting of spin-wave beams, along with the extended non-diffracted beam propagation distance, highlight the potential application of these effects in spin-wave multiplexers for magnonic logic devices.

Control of spin wave transport in polymer 3D films was realized by magnetic microvolcanoes embedded in waveguides, fabricated by soft-matter specific techniques. Propagate of the spin wave signal excited in yttrium iron garnet (YIG) with 3D self-standing microvolcanoes chambers on top filled by the magnetic nanoparticles was evaluated by Brillouin light scattering and microwave spectroscopy. The magnetic moment of the polymer microvolcanoes varied with the change of the magnetic field bias direction inside the YIG films, which was shown by 2D mapping of the outer surface of the films. The good correlation of micromagnetic modeling and experimental data of spin wave propagation in the multistructure as a function of the applied magnetic field was clarified by the convergence parameters of the obtained polymer 3D magnetic microvolcanoes fields and the standard theory of spin wave propagation. The uniqueness of the soft materials object—polymer magnetic 3D films on conductive YIG film—lies in the application of the magnon network properties, which may find application in biomedical high-sensitivity feedback sensors.

In this work, we present the results of investigations performed on hematite (α-Fe2O3), which is an antiferromagnet with weak ferromagnetism. Through the use of Brillouin light scattering spectroscopy, we studied experimentally the excitation of quasi-ferro- and antiferromagnetic modes in the bulk hematite. We investigated the influence of relative mechanical strains, ϵyy, on the frequencies of quasi-ferro- and antiferromagnetic modes. Also, we considered the angular dependence of the frequency of the quasi-ferromagnetic mode on the external magnetic field. Our results indicate that hematite is a suitable material for strain-controlled magnonic devices.

When an electric current flows through the NiFe/IrMn structure, a significant redistribution of the intensities of the direct Stokes and inverse anti-Stokes lines in spectra of Brillouin scattering on thermal spin waves is observed. This is due to a change in the orientation of uniaxial anisotropy and the corresponding easy axis of the exchange shift under the action of the spin–orbit torque in the IrMn antiferromagnet, which in turn affects the dynamics of spin waves in the neighboring ferromagnetic NiFe layer. The detected effect indicates that spin-wave processes in a ferromagnet can be controlled by applying a spin current to change the magnetic anisotropy of the NiFe/IrMn interface.

A magnon-assisted electrically driven “mirror” with tuned frequency of the reflected light is created. The effect of in-plane electric current on asymmetry of Stokes–anti-Stokes Brillouin intensities in NiFe/IrMn exchange-biased patterned structures is found. Electric current directed along external magnetic field suppresses anti-Stokes component in Brillouin light-scattering spectra, while the opposite direction of current results in suppression of the Stokes component. We show that spin currents arising in the IrMn layer induce spin-orbit torque affecting uncompensated antiferromagnetic moments at the interface, rotate the antiferromagnetic moments, change bias field, and finally determine direction of dominating spin-wave propagation. The possibility of electric control of spin-wave direction and manipulation over Stokes and anti-Stokes intensities opens a way for design of electro-optical devices switching light frequency.

Here we report recent data on the phenomenon of total nonreflection of spin waves (NRSWs). Using space- and phase-resolved Brillouin light scattering we experimentally studied the amplitude, direction, and phase of the NRSW in yttrium iron garnet films with artificial defects—an antidot array. An NRSW in the form of a focused beam of high intensity with the group velocity pointing along the line of defects is observed only for a critical angle between spin-wave phase velocity and an antidot array direction in a magnetic field. It is shown that the NRSW is an independent noncollinear spin wave arising as a result of the anisotropic nature of the propagation of surface magnetostatic spin waves in a magnetic medium. The numerical simulations agree well with experimental data. Micromagnetic simulations performed let us elucidate the phenomenon of the NRSW and map the spin-wave profile of dynamic magnetization inside the NRSW. The estimated mean free path of the NRSW reaches about 1 mm in the yttrium iron garnet film with a thickness of a few micrometers. These results demonstrate a unique approach to focusing and enhancing spin waves in magnetics through the use of artificial defects.