A. P. Kuz’menko

Elastically induced mechanism of magnetization reversal in orthoferrites

In weak ferromagnets-orthoferrites in magnetic fields, which are considerably less than the spin-flop field, a new mechanism of magnetization reversal has been experimentally revealed. This is shown to be accompanied by the nonsteady motion of the domain wall whose velocities exceed the limiting velocity.

Magnetoelastic waves in yttrium orthoferrite plates

We have experimentally studied surface magnetoelastic waves in yttrium orthoferrite plates and discovered the phenomenon of energy pumping from the initial frequency (∼1 kHz) to higher harmonics (∼12.5 kHz).

Resonance retardation of a domain wall by Winter magnons in orthoferrites

Supersonic domain-wall dynamics is investigated in wafer samples of YFeO3 having thicknesses of 10 µm, 35 µm, 40 µm, 120 µm, and 125 µm, prepared by different methods, and in a EuFeO3 sample of thickness 60 µm at liquid-nitrogen temperature. Relations are established for the occurrence of nonlinear segments in the form of constant-wall-velocity intervals in the dependence of the wall velocity on the pulsed magnetic field amplitude. Qualitative agreement is obtained between the experimental data and calculated values of the velocities and widths of the constant-velocity intervals, on the assumption that the mechanism of resonance retardation of the domain walls by parametrically excited Winter (wall as opposed to bulk) magnons is operative at supersonic velocities.

Retardation of a moving domain wall in weak ferromagnets

The retardation of a single domain wall in its motion at subsonic and supersonic velocities in YFeO3 and FeBO3 plates is investigated using the magneto-optical Faraday effect. The experimental results are discussed with due regard for the interaction of the magnetic and elastic subsystems of the crystal.

Dynamical self-organized periodic superstructures in supersonic dynamics of domain wall in orthoferrites

Abstract It is found that the domain wall motion at supersonic velocities in orthoferrites is in line with characteristics of dynamic self-organized systems. It is also observed that the transition between two neighbouring ranges Δ H i →Δ H i +1 of a magnetic field on the graph of the domain velocity versus the magnetic field— V ( H ) is accompanied by a reduction in size of periodic superstructures on the domain wall, λ i → λ i +1 . In this case, the domain wall velocity changing abruptly in the transitions between Δ H i is a bifurcation parameter.

Diffraction of light by dynamic elastic deformations of a moving domain wall in orthoferrites on breaking through the sound barrier

Diffraction of light by dynamic deformations of a domain wall moving at the velocity of sound is observed in plates of rare-earth orthoferrites TmFeO3 and DyFeO3. In this case, the domain wall is shown to become bent across the thickness of the plate. The lifetime of the dynamic deformations is determined to be 20 ns, and their dimension is 2×10−4 cm. It is found that the polarization of light is altered and its change is comparable in magnitude to the Faraday rotation angle in the orthoferrites investigated.

Nonlinear magnetoacoustic interactions in weak ferromagnets

The pinning and interaction of a single domain wall with normal magnetoelastic waves excited during its motion in a single-crystal yttrium orthoferrite plate, were discovered and investigated by a method based on the magneto-optical Faraday effect. The dependences of the bending wave amplitude and the spectra of shear waves, which can be excited by a moving domain wall, were calculated. The results obtained are interpreted with allowance for the interactions of excited oscillations in both the magnetic and elastic subsystems of the orthoferrite.

Specific features in supersonic nonlinear dynamics of domain walls in rare-earth orthoferrites

The dynamics and temperature dependences of the mobility of domain walls in EuFeO3 (from 4.2 to 300 K), TmFeO3 (from 100 to 300 K), LuFeO3 (300 K), YFeO3 (460 K), and DyFeO3 (from 77 to 300 K) orthoferrites are investigated in pulsed magnetic fields H up to 4.8 kOe. It is found that the field dependence of the domain wall velocity v(H) in all these compounds exhibits a nonlinear behavior and consists of discrete portions corresponding to the magnetic field ranges ΔHi in which the domain wall moves at a constant velocity. The appearance of these features in the ΔHi ranges is associated with magnetoelastic and flexural oscillations generated by domain walls in a strongly dissipative nonlinear medium. It is revealed that the domain wall dynamics at supersonic velocities has a non-one-dimensional character. At the instant the domain wall breaks through the sound barrier, the domain structures undergo a nonstationary transformation with changes in the fine structure of the domain walls. The interface motion is accompanied by self-organizing processes.