Yu. A. Filimonov

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.

Standing spin waves in magnonic crystals

The features of standing spin waves (SWs) excited during ferromagnetic resonance in three different one-dimensional magnonic crystals (MC) are intensively studied. The investigated magnonic crystals were: an array of air-spaced cobalt stripes, an array of air-spaced permalloy (Py) stripes, and a bi-component MC composed of alternating Co and Py stripes. All MC structures were made by etching technique from Co and Py thin films deposited onto Si substrates. Two configurations are considered with the in-plane external magnetic field applied parallel or perpendicular to the stripes. The supporting calculations are performed by the finite element method in the frequency domain. A number of intensive SW modes occurred in periodic structures under ferromagnetic resonance conditions as a consequence of standing spin waves excitation. These modes were analyzed theoretically in order to explain the origins of SW excitations. With the support of numerical calculations, we analyze also the possible scenarios for the occurrence of standing SWs in the investigated structures. It is demonstrated that the SW propagation length is an important factor conditioning the standing SW formation in MCs.

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.

Magneto-Photonic and Magnonic Crystals Based on Ferrite Films - New Types of Magnetic Functional Materials

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.

Ferromagnetic resonance in submicron permalloy stripes

Abstract We present systematic experimental investigation and micromagnetic simulation of ferromagnetic resonance (FMR) in planar rectangular permalloy microstripes. The experimental microwave absorption was studied for different sample orientations in an external magnetic field. To analyze the FMR modes we developed the algorithm for the simulation of spectrum and spatial distribution of magnetization oscillations in dependence on swept external magnetic field based on numerical solution of Landau-Lifshitz-Gilbert equation. It was shown good agreement between experimental and model FMR spectra that enables the reliable visualization for spatial distributions of oscillating magnetization in modes of spin-wave resonances for different excitation conditions.

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.

Magnetron sputtering of thin Cu(200) films on Ni(200)/SiO2/Si substrates

The possibility of oriented growth of thin copper films with a (200) texture on a SiO2/Si substrate by magnetron sputtering in medium vacuum is demonstrated for the case when a predeposited nickel layer with a (200) texture serves as an orienting sublayer.

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.