A mixed domain structure in ferrite-garnet films

A stable static mixed domain structure consisting of strip domains and a cylindrical magnetic domain (CMD) is obtained in (Bi_0.7Lu_0.3)₃ (Fe_0.8Ga_0.2)₅ O₁₂ ferrite-garnet films. An analytic theory of the mixed domain structure is constructed. An analytic solution is obtained for the shape of a distorted strip domain, which is in good agreement with experimental results.     

Surface fastening of domain boundaries in epitaxial ferrite-garnet films

The process of quasistatic shifting of domain boundaries (DB) in weak magnetic fields is studied in epitaxial ferrite-garnet films (EFGF). The investigations were performed by using the Faraday magnetooptical effect by the method of domain boundary oscillation in a variable magnetic field and by recording small shifts in a permanent field. Artificial fastening of EFGF DB is performed on the film surface-air by fields of scattering from a thin MnBi layer deposited on the EFGF with a different magnetization state. The assumption of DB fastening in EFGF on the film-substrate transition layer is confirmed experimentally. The influence of the transition layer characteristics on the magnitude of the EFGF coercive force is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, No. 11, pp. 52–57, November, 1989.The author is deeply grateful to A. G. Shishkov for discussing the research.     

Unidirectional anisotropy of the velocity of domain walls in ferrite-garnet films

A mechanism to explain the gigantic unidirectional anisotropy of the velocity of domain walls, which includes the local rotation of the magnetization in front of a moving domain wall, initiated by radiated spin waves is proposed. Institute of General Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 45–48, September, 1997.     

On the local magnetization reversal in front of a domain wall moving in a garnet ferrite film with orthorhombic magnetic anisotropy

The experimentally observed shapes of dynamic domains in garnet ferrite single-crystal films with (110) and (210) orientations are explained in terms of in-plane magnetic anisotropy of these films.     

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.     

Spin waves in a ferromagnet with a moving domain wall

An exact solution of the equation for spin waves propagating along the normal to the domain wall is derived for a ferromagnet with a 180° domain wall moving at constant speed, and the radiation of spin waves in rf fields is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 66–69, April, 1979.     

Dynamics of domain walls in orthoferrites in the light of results obtained for ferrite-garnet films

Results obtained for monocrystalline films of ferrite-garnets (FGMFs) are used to explain why the generation of microdomains ahead of a moving domain wall (DW) has been observed for orthoferrites in experiments involving the dynamic growth of multiple domains but has not been seen in experiments in which the motion of an isolated DW was studied. The explanation is based on the dependence of the dimensionless decay parameter on the constant magnetic field applied in the plane of the film (plate). Institute of General Physics of the Russian Academy of Sciences, at Mordovia State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 1, pp. 59–63, January, 1999.     

Anomalies of magnetooptical diffraction in ferrite-garnet films

Experimental magnetooptical diffraction spectra produced by the band domain sructure in an epitaxial ferrite-garnet film are described. Asymmetry of the optical field in symmetric maxima is observed when a laser beam is normally incident on the sample. Analysis of the experimental data shows that the factors responsible for disrupting the symmetry of the magnetooptical diffraction spectrum include the inclination of the domain walls and inequality of the Fresnel coefficients fors andp polarizations of the incident radiation. Ul'yanovsk State Unviersyt. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 68–71, September, 1997.     

The initial stage in the nonlinear motion of a domain wall in garnet films

A study of the domain-wall motion in single-crystal garnet films of the YBiFeGa system with a perpendicular magnetic anisotropy, activated by a constant in-plane bias field H _p parallel to the wall plane and a pulsed drive field H _g of an amplitude corresponding to the nonlinear region of the domain-wall velocity vs. the H _g relation is reported. The earlier data suggesting the existence of an initial phase of motion, where the wall is accelerated to a high instantaneous velocity, have been confirmed. The wall behavior in the initial phase has been shown to be affected by the field H _p and the drive-field pulse rise time. A possible mechanism of the wall structure transformation after the application of the H _g pulse is considered. It has been established that the dependence of the wall velocity on H _p in the saturation region disagrees with theory.     

Dynamics of a domain wall coupled to thermally agitated spins: A model of a rare earth ferrite-garnet

The nonlinear mobility of a domain wall in an idealized model of a RE ferrite-garnet is considered, the thermally agitated RE sublattice being described by the Landau-Lifshitz-Bloch equation [4] with longitudinal relaxation terms. It is shown that in some field intervals the DW velocity is small and governed by the longitudinal relaxation of the RE ions. This effect may be observed in sufficiently low magnetic fields near the compensation point of ferrites. If the dynamics of the RE spins is dissipationless, there is a non-analytic contribution to the DW damping due to the wake in the RE subsystem.     

Study of the fast dynamics of domain walls in ferrite-garnet films in the presence of large in-plane fields

The dynamics of domain walls in ferrite-garnet films with orientation (111) was investigated by twofold digital high-speed photography. The experiments were performed in the presence of an in-plane magnetic field comparable to the anisotropy field of the samples.     

Microinhomogeneities in the distribution of oxygen concentration in ferrite-garnet films

Artificial microinhomogeneities were created in iron-garnet (TmBiCa)₃(FeGa)₅O_12−γ films with various degrees of oxygen nonstoichiometry, changes in the individual magnetic characteristics of these inhomogeneities were tracked during chemical oxidation and reduction, and the interactions of these inhomogeneities with planar domain walls and spiral domains were investigated. The resulting experimental data were interpreted by analyzing how the saturation magnetization, domain-wall surface-energy density, and uniaxial anisotropy constants depended on the concentrations of different-valency iron ions, cationic vacancies, and anionic vacancies. Fiz. Tverd. Tela (St. Petersburg) 41, 2016–2019 (November 1999)     

Excitation of spin waves localized on a moving domain wall in a two-layer ferromagnetic film

The problem of excitation of spin waves in a two-layer magnetic film with a sharp interface between the layers is solved on the basis of Slonchevskii equations. The equations describing spin wave excitation along the film thickness are derived. The results are limited to zeroth approximation in the smallness parameter ɛ, viz. the ratio of the energy of magnetic dipole forces to the anisotropy energy. The power dissipated by such oscillations is calculated.     

Interaction of a moving domain wall with surface magnetoelastic waves in yttrium orthoferrite

The amplitude-frequency characteristics of magnetoelastic surface waves excited by moving domain walls in a lamellar yttrium orthoferrite samples are discovered and measured. The results of analysis of the effect of magnetoelastic surface waves on the dynamics of domain walls in this orthoferrite are considered. The nonlinear interaction between magnetoelastic surface waves accompanying a moving domain wall is analyzed.     

Effect of temperature on the formation of dynamic magnetic domains in ferrite-garnet films

Dynamic domain structures in ferrite-garnet films (111) with normal anisotropy are investigated for the temperature range of 77–300 K. The boundaries of the area of the existence of one- and two-armed spiral domains are determined as a function of the temperature, frequency, and amplitude of the vertical field. It is found that the region of the existence of spiral dynamic domains shift toward low frequencies when the temperature is reduced.     

Electroacoustic waves confined by a moving domain wall superlattice of a ferroelectric crystal

The dispersion properties of electroacoustic wave modes confined by a superlattice of uniformly moving 180° domain walls in a tetragonal ferroelectric crystal are considered. It is shown that the manifold of partial electroacoustic interfacial waves in the lattice is restricted to the first allowed band, the configuration of which in the plane of spectral variables can significantly vary under the action of the moving domain walls.     

High-drive-field domain wall dynamics in low-damping garnet films

Domain wall (DW) dynamics in a low-damping YBiFeGa film with perpendicular magnetic anisotropy was studied under FMR conditions. Measurements were carried out under radial expansion of magnetic bubbles in high pulsed drive fields and in an in-plane de magnetic field. A high-speed image recording technique was employed. The pattern of the dependence of DW velocity on drive field for the parts of the DW oriented parallel and perpendicular to the in-plane field was established. In all cases, this dependence contains a saturation region in which the DW velocity increases noticeably with increasing in-plane field. The experimental data obtained do not agree with theory. A possible explanation for this discrepancy is proposed. The onset of spatially periodic distortions in a moving DW is discussed.     

Excitation of bending vibration by a moving domain wall in a plate of yttrium orthoferrite

Elastic vibrations have been experimentally found induced by a moving domain wall in a sample of yttrium orthoferrite 10⁻⁴ m thick. Calculations have been carried out to suggest their relevance to flexural Lamb waves.     

Interaction of a shear wave with a moving domain wall in an iron garnet crystal

The boundary-value problem of the interaction of a plane monochromatic shear wave with a moving Bloch wall in an iron garnet crystal is solved in the framework of the nonexchange magnetostatic approximation on the basis of the method of phase invariants for wave problems with moving boundaries. For a shear wave incident on the domain wall, the possibility of the reflectionless birefringence is demonstrated. Numerical results illustrating the resonance properties of the magnetic subsystem are presented. It is established that, at the upper bound of the reflectionless birefringence range, the interaction of the shear wave with the domain wall manifests itself as a degenerate resonance with the solution in the form of two combined antiphase, collinearly propagating shear waves of infinitely large amplitudes, which form a zero resulting field.     

Determination of the losses induced by irreversible barkhausen jumps of the 180° domain wall moving with a sinusoidal motion in the single domain wall model

The paper presents an analysis of the losses due to irreversible Barkhausen jump of the 180° Bloch wall in the single-domain wall model. The field-intensity and current-density vectors at unit input were determined for a single instantaneous jump. The losses were calculated for the case of the wall moving sinusoidally. The Parseval formula was used at determining the losses, which made it possible to perform calculations. A similar problem was considered by Allia and Vinai who adopted a simplified assumption of the domain of an infinitely long cylindrical shape.