G. T. Kazakov

Four-magnon decay of magnetostatic surface waves in yttrium iron garnet films

The four-magnon instability of magnetostatic surface waves (MSSWs) in yttrium iron garnet epitaxial films is investigated experimentally. It is shown that four-magnon instability for MSSWs with wave numbers 30–600 cm−1 is a decay instability and develops for values of the wave magnetization close to the threshold level for second-order parametric instability of a homogeneous transverse pump wave. When the supercriticality of the MSSW power is 15–20 dB, the generated parametric spin waves themselves become unstable with respect to the four-magnon interaction, so that kinetic instability develops in the film. It is shown that the pump signal transmitted through the signal and the length of the “nonlinear” part of the film, where a MSSW is capable of exciting parametric spin waves, increase as the pump power is increased.

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.

Evidence of the exchange coupling effect in the spin wave spectrum of a structure with two different magnetic layers

Abstract The spin wave resonance (SWR) spectrum of a structure with two different magnetic layers was investigated by means of an experimental technique based on the effect of resonant interaction of magnetostatic Damon-Eshbach and exchange waves. We show that in the presence of exchange coupling, the frequency position and intensity of SWR lines oscillate during magnetic field variation. These oscillations are due to the ‘repulsion’ effect of the SWR lines, which takes place at frequencies corresponding to the coincidence of single-layer spectrum frequencies.

Magnetic crystallographic anisotropy of Fe/GaAs(100) epitaxial films

An investigation was made of the anisotropic properties of Fe films obtained by molecular-beam epitaxy on GaAs(100) substrates. It is shown that at thicknesses t=40–50 Å the Fe films begin to exhibit cubic magnetic anisotropy. At thicknesses t>100 Å the first constant of cubic anisotropy K1 has values similar to those for “bulk” Fe single crystals. Films of intermediate thickness 50<t<100 Å possess both isotropic and anisotropic phases.

The effect of parametrically excited spin waves on the dispersion and damping of magnetostatic surface waves in ferrite films

This paper describes an experimental study of variations of the dispersion and damping of magnetostatic surface waves in ferrite films, caused by three-and four-magnon interactions with parametric spin waves excited by an auxiliary surface magnetostatic pump wave with frequency fp. The variations in the dispersion and damping were identified, respectively, with variations Δk″ in the real part and Δk′ in the imaginary part of the wave number of the surface magnetostatic wave. The Δk″ and Δk′ values were determined from the ratio of the changes of the phase increment Δφ and the amplitude increment ΔA of the surface magnetostatic wave to the length L of the nonequilibrium section of the film, where the parametric spin waves exist. It is found that, when three-magnon decay processes are allowed for the pump wave and the surface magnetostatic probe wave, the probe wave can substantially alter the distribution of the parametric spin waves in the film.

Nondispersive delay line on magnetostatic waves

A new approach to the design of a nondispersive delay line on magnetostatic waves is proposed, whereby the cascades operating on the surface waves and the backward volume waves have a common passband in the same magnetic system due to a difference in the crystallogrphic orientations of ferrite waveguides cut from a {100} yttrium iron garnet film. The possibility to obtain a pulse delay time of up to 113 ± 3 ns in a 300-MHz-wide frequency band is experimentally demonstrated. The central frequency of this band can be tuned within 4–6 GHz by changing the applied magnetic field.

Interaction of a post-threshold signal and a weak microwave signal during passage through a ferrite-film noise suppressor

The interaction of a post-threshold signal and a weak signal in a noise suppressor based on a microstrip line loaded with an yttrium-iron-garnet (YIG) epitaxial film is studied experimentally. It is demonstrated that anomalous fragments may emerge in the weak-signal transmission spectrum at frequencies that correspond to the excitation of magnetostatic surface waves (MSSWs) in the YIG film in the presence of a post-threshold signal with supercriticality C of ≈ 7–30 dB. The frequencies that correspond to these fragments may differ from the frequency of the post-threshold signal by 10–400 MHz and are equal to the frequencies corresponding to the anomalous fragments in the dispersion relation of a weak MSSW.

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.

Oscillations of surface acoustic Rayleigh wave transmission on Ga, Sc-substituted yttrium iron garnet films

Resonant interaction between surface acoustic Rayleigh wave and backward volume magnetostatic wave on Ga, Sc-substituted yttrium iron garnet films was experimental studied. For the first time, an oscillation of SAW parameters caused by resonant interaction with backward volume magnetostatic wave modes of several numbers was observed.

The effect of GaAs(001) substrate roughness on the magnetic properties of epitaxial Fe films

The effect of GaAs(001) surface roughness on the magnetic properties of MBE-grown Fe films having a thickness t in the interval from 12 to 140 Å is investigated by the ferromagnetic resonance method. The films were deposited at room temperature with rates of 9 and 3 Å/min. For films grown on substrates with the rms deviation of the roughness σ≈10 and 30 Å, the spectrum is essentially dependent on the relationship between t and σ. At t≤σ and t≥3σ, a single absorption line is observed, whereas at σ≤t≤3σ, two absorption lines are present. These features of the spectra are related to the island growth of the films and the influence of roughness on island coalescence.