Magnetic structure and resonance properties of a hexagonal lattice of antidots

Abstract

Static and resonance properties of ferromagnetic films with a hexagonal lattice of antidots (pores in the film) were studied. The description of the system is based on micromagnetic modeling and analytical solutions of the Landau–Lifshitz equation. The dependences of ferromagnetic resonance spectra on the in-plane direction of applied magnetic field and on the lattice parameters were investigated. The nature of the dependences of a dynamic system response on the frequency at fixed magnetic fields and on the field at fixed frequency when the field changes were explored. They cause the static magnetic order to change. It was found that the specific peculiarities of the system dynamics remain unchanged for both of these experimental conditions. Namely, for low damping the resonance spectra contain three quasi-homogeneous modes which are due to the resonance of different regions (domains) of the antidot lattice cell. It is shown that the angular field dependences of each mode are characterized by a twofold symmetry, and the related easy axes are mutually rotated by 60 °. As a result, a hexagonal symmetry of the system’s static and dynamic magnetic characteristics is realized. The existence in the resonance spectrum of several quasi-homogeneous modes related to different regions of the unit cell could be fundamental for the function of the working elements of magnonics devices.

Generation of propagating spin waves from regions of increased dynamic demagnetising field near magnetic antidots

“…This approximation (a more rigorous development of which is beyond the scope of this letter) allows us, e.g., to understand qualitatively the presence of quasi-uniform resonance modes confined above and below the antidot. 27,35 Moreover, as would be expected from Fig. 1(c), the regions left and right of the antidot reveal an increase in the local frequency, which then tends in a graded fashion 24 towards the FMR frequency of the continuous film (2.98 GHz).…”

“…Following the approach from Ref. 27, we can neglect the wave-vector dependent contributions to the effective magnetic field and calculate the distribution of the "local FMR frequency" (referred to as "local frequency" in the following) on a cell-by-cell basis, as shown in Fig. 2(a).…”

“…Then, we use a microstrip antenna with a width much greater than the antidot diameter to excite a high-frequency magnetic field that is approximately uniform in the vicinity of the antidot. The frequency of this harmonic field is tuned to selectively match the local resonance frequencies 27 of specific localized regions adjacent to the antidot. When the frequency exceeds that of the uniform ferromagnetic resonance (FMR) in the rest of the YIG film, the resonating regions do not support confined spin-wave modes but form instead localized point-like sources of spin waves propagating into the continuous film.…”

An effect of the curvature induced anisotropy on the spectrum of spin waves in a curved magnetic nanowire

“…[7][8][9][10][11] Recently there is a large number of works devoted to the study of one-and two-dimensional planar magnon crystals formed by periodic structuring of monolayer magnetic films, most often yttrium iron garnet 12,13 or transition metals. [14][15][16] However, since in the magnon devices the topology is essential, it is necessary to study properties of connections between different parts of structural elements of magnonic devices and metamaterials. This gives rise to the renewed interest in the theoretical study of curved low-dimensional systems.…”

Magnetic interfaces as sources of coherent spin waves

“…For the same reason, no spin-wave emission is possible if the source term = (14) becomes equal to zero for any other reason. Depending on the problem, the local microwave susceptibility tensorsχ A(B) in the vicinity of the interface can be calculated analytically [23] or from micromagnetic simulations [22,24]. The most efficient emission is expected when the source term is strongest.…”