S. L. Vysotsky

Observation of magnonic band gaps in magnonic crystals with nonreciprocal dispersion relation

An effect of metallization of a magnonic crystal surface on band-gap formation in the spectra of a surface spin wave (SSW) is studied both theoretically and experimentally. The structures under consideration are one-dimensional magnonic crystals based on yttrium iron garnet with an array of etched grooves, with and without a metal screen on the top of the corrugated surface. Due to nonreciprocity of propagation of the SSW, the shift of the band gap to higher frequency and from the border of the Brillouin zone in the presence of a conducting overlayer was measured in a transmission line experiment. Results of numerical calculations and model analysis are in agreement with experimental data and give further insight into the origin of the band gap and properties of the nonreciprocal SSW in metalized magnonic crystals. This gives a positive answer to the outstanding question about the possibility of detection of magnonic band gaps in the spectra of spin waves with nonreciprocal dispersion in magnonic crystals, and creates the potential for new applications and improvements of already existing prototype magnonic devices.

Ferromagnetic resonance investigation of permalloy particles array structures

The measurements of ferromagnetic resonance spectra of tangentially magnetized arrays of micron size rectangular particles of permalloy produced by electron-beam lithography are reported. In contrast to continuous films, the spectra of arrays include a number of additional resonance peaks associated with spin-wave modes in the particles. The number of the peaks and their position depends on the angle between the direction of the bias magnetic field and the array axis. The magnetic structure of the particles was investigated using magnetic force microscopy. Magnetization reversal processes of the array were investigated using magneto-optic Kerr effect.

Magnetic properties of thermally deposited Fe/GaAs(100) thin films

Thin (50–200 Å) films of iron have been prepared on (100) gallium arsenide substrates by thermal evaporation at a deposition rate of 3–30 Å/s and a pressure of ∼10−5 torr. Dependences of the saturation magnetization, cubic and uniaxial planar anisotropy constants, and the ferromagnetic resonance linewidth on the film thickness were studied by ferromagnetic resonance at 9.8 GHz. It has been found that the parameters of thermally deposited Fe/GaAs (001) films are comparable to those achieved with molecular-beam epitaxy.

Ferrite waveguides’ array as a model of magnonic crystal

The possibility of magnonic crystal spin-wave spectra representation as a result of interaction of spin-wave excitations of narrow ferrite profiled waveguides is shown. Micromagnetic simulation was used to investigate the dependence of magnonic crystal internal magnetic field distribution on the direction of magnetisation.

Influence of growth temperature on the easy magnetization axis switch and domain structure in Fe/GaAs(100) structures

Dependence of the easy magnetization axis switch and domain structure in Fe films grown on GaAs(100) substrates on the growth temperature TS and deposition rate υ was investigated. The easy magnetization axis direction was determined from ferromagnetic resonance measurements in tangentially magnetized Fe films. It was found for films grown at substrate temperature TS ≤;140°C that with decreasing films thickness t smaller some critical thickness t* the easy magnetization axis direction switches from [100] to [110] crystallographic axis while for films grown at substrates temperatures Ts>140°C the easy magnetization direction was along [100] axis at decreasing the film’s thickness down to 10 Å. The critical thickness t* of “switched” film nonmonotonically depends on the deposition rate and was determined at t* ≈ 21, 15 and 28 Å for deposition rates υ ≈1.4 ; 3 and 4 Å/min, respectively. Domain structures in FeGaAs(100) films are discussed.

Layered thin-film magnetic structures as a basis of spintronic element base

The technology and diagnostics of thin film magnetic structures are reported, in the context of investigations of spin-dependent electron transport effects, for use in the design of magnetic storage devices. The achieved parameters are reported and discussed.