S. L. Vysotskii

Ferromagnetic films with magnon bandgap periodic structures: Magnon crystals

A new type of photonic crystals is proposed. The new crystals have a forbidden gap in the microwave spectrum of magnetostatic spin waves, and, by analogy with photonic crystals, they are called magnon crystals. Specimens of such crystals were fabricated on the basis of yttrium iron garnet films. The surfaces of ferromagnetic films containing two-dimensional etched hole structures were studied by atomic force and magnetic force mag-netometry. The propagation of spin waves through the magnon crystals was investigated.

Magnetostatic spin waves in two-dimensional periodic structures (magnetophoton crystals)

Series of experiments are carried out to study the propagation of magnetostatic spin waves in ferromagnetic films containing 2D periodic structures formed by etched apertures. For spin waves, such films are analogous to photon crystals (namely, magnetophoton or magnon crystals). The spectra of waves transmitted through the structure display features associated with a change in the spin homogeneity due to etching or radiation loss, as well as with Bragg reflection effect or the emergence of forbidden gaps in the spectrum of propagating waves.

Bragg resonances of magnetostatic surface spin waves in a layered structure: Magnonic crystal-dielectric-metal

It is experimentally shown that metal cladding of the surface of a one-dimensional magnonic crystal destroys the Bragg band gaps in microwave transmission spectra of propagating magnetostatic surface spin waves in magnonic crystal. This is a consequence of violating a phase synchronism condition of forward and reflected by a magnonic crystal magnetostatic surface wave. When a magnetostatic surface wave propagates in a layered structure, ferromagnetic film with a magnonic crystal-dielectric layer-metal cladding this synchronism condition can also be fulfilled, not depending on the thickness of a dielectric layer.

Effect of ferrite magnonic crystal metallization on Bragg resonances of magnetostatic surface waves

It is experimentally established that metallization of the surface of a ferrite magnonic crystal destroys the Bragg resonances of magnetostatic surface waves by violating the conditions of phase synchronism of the incident wave and that reflected from the periodic surface structure.

The spectrum of the spin-wave excitations of the tangentially magnetized 2D hexagonal ferrite magnonic crystal

The spectrum of the spin-wave excitations (SWEs) that are localized in a unit cell of the tangentially magnetized 2D ferrite magnonic crystal is experimentally and numerically studied. The groups of SWEs that are localized in the central part of the unit cell and in the regions of the magnonic crystal parallel to its axes are identified.

Bragg resonances of magnetostatic surface waves in a ferrite-magnonic-crystal-dielectric-metal structure

Formation of Bragg resonances of surface spin waves (SSWs) propagating in a magnonic-crystaldielectric-metal (MC-D-M) structure is studied. It is shown that, in an MC-D-M structure with a finite dielectric interlayer of thickness t, Bragg resonances of the SSWs with the wavenumbers k < 1/t can be destroyed whereas the resonances of the SSWs with k > 1/t persist and lead to formation of rejection bands in the wave spectrum.

Hybridization of spin-wave modes in a ferromagnetic microstrip

The dependence of the spectrum of spin-wave modes (SWMs) in a permalloy microstrip on the angle θ between the microstrip axis and the direction of the in-plane bias magnetic field has been studied with the use of ferromagnetic resonance at a frequency of 9.85 GHz. Hybridization between the quasi-homogeneous SWM and weakly localized SWM, which manifests itself as the repulsion of absorption lines of the microstrip spectrum, has been discovered at the angle θ ≈ 70°. The experimental results are in fair agreement with the numerically calculated SWM spectrum.

Magnetostatic volume waves in exchange-coupled ferrite films

The influence of exchange coupling of layers on the propagation of magnetostatic dipole volume waves in normally and tangentially magnetized two-layer epitaxial ferrite structures is investigated. It is shown that the indicated influence is manifested in the form of dynamic spin pinning effects on the interlayer boundary and formation of a common dipole-exchange wave spectrum for the entire structure. In this case, at the synchronism frequencies of the dipole and exchange waves the losses of the dipole waves grow and anomalous segments appear in the dispersion. In films magnetized in the “hard” direction relative to the axis of normal uniaxial surface anisotropy the magnetostatic dipole volume waves can interact resonantly with the surface spin waves supported by the boundaries with pinned spins.

Surface spin waves in one-dimensional magnonic crystals with two spatial periods

We have experimentally studied the propagation of spin surface waves (SSWs) in a one-dimensional magnonic crystal comprising two planar periodic structures—a lattice of grooves etched on the surface of an yttrium iron garnet (YIG) film and a lattice of metal stripes, separated by a dielectric spacer. It is established that the frequency dependence of the SSW transmission coefficient depends on the overlap of bandgaps determined by the Bragg resonances of SSWs on both lattices and can be modified by changing the mutual orientation of wave vectors of the two lattices and/or the dielectric spacer thickness.

YIG Thin Film-Based Two-Dimensional Magnonic and Magneto-Photonic Crystals

A new type of photonic crystals entitled “magnonic crystals (MC)” that exhibit forbidden gaps in the microwave spectrum of magnetostatic spin waves (MSW) are reported. The topography of the MCs that consist of two-dimensional (2-D) etched holes periodic structure in yttrium iron garnet films was studied by atomic force and magnetic force magnetometry. The propagation characteristics of spin waves in such 2-D MCs was measured and analyzed.