A. S. Logginov

Magnetoelectric control of domain walls in a ferrite garnet film

A displacement of magnetic domain walls under the effect of an electric field is observed in epitaxial ferrite garnet films (on substrates with the (210) orientation). The displacement of the domain walls changes to the opposite when the electric field changes sign, and it is independent of the direction of magnetization in the domains. The mechanism proposed for explaining the observed phenomenon is based on the inhomogeneous magnetoelectric effect.

Room temperature magnetoelectric control of micromagnetic structure in iron garnet films

The effect of magnetic domain wall motion induced by electric field is observed in epitaxial iron garnet films grown on (210) and (110) gadolinium-gallium garnet substrates. The displacement of the domain wall changes to the opposite at the reversal of electric field polarity, and it is independent of the magnetic polarity of the domains. Dynamic observation of the domain wall motion in 400 V electric pulses gives the domain wall velocity of about 50 m/s. The same velocity is achieved in a magnetic field pulse of about 50 Oe. This type of magnetoelectric effect is implemented in single phase material at room temperature.

Multiferroics: Promising materials for microelectronics, spintronics, and sensor technique

Possible areas of application of magnetoelectric materials and multiferroics in microelectronics, spintronics, and sensor technique are considered. Criteria of practical applicability of such materials are formulated and examples of magnetoelectric materials satisfying these criteria are given.

Direct optical observation of vertical Bloch lines propagation by in-plane field pulses

Vertical Bloch line (VBL) motion in response to in-plane field pulses is studied by the methods of polarized anisotropic dark field observation (PADO) and high-speed photography in bubble garnets. The mobility of VBLs and their velocities are measured. New types of PADO pictures which are connected with the dynamic changes of VBL and domain wall structures are observed in the nonlinear region of Bloch line motion. A difference in the dynamic behavior of VBLs of different types is observed. A qualitative discussion of the origin of PADO contrast features and VBL behavior difference is proposed. >

Generation of mesoscopic magnetic structures by local laser action

New effects are observed wherein the internal structure of the domain walls in a thin magnetic iron garnet film are modified by the action of focused laser radiation. A single laser pulse with increasing power gives rise to the following: 1) displacement of vertical Bloch lines in a domain wall; 2) generation of a pair of vertical Bloch lines on initially line-free walls; and, 3) an irreversible change in shape of a domain wall and the domain structure as a whole. The mechanism leading to the generation and displacement of Bloch lines is connected with the motion of domain walls which is induced by a local change in the distribution of demagnetizing fields as a result of a heating-induced decrease of the magnetization in the focal spot of the laser radiation.

InGaAs strained-layer single-quantum-well lasers' spontaneous emission spectra and their features

The existence of equidistant smooth maxima series was found in the spontaneous emission spectra of stripe single-quantum-well 0.98 micrometers range lasers with a strained InGaAs active layer. Within the limits of a 200 angstrom wide general envelope the characteristic distance between maxima for different lasers varied from 20 to 40 angstrom, corresponding to 10 to 20 longitudinal Fabry-Perot cavity mode intervals. Possible physical models of observed maxima origin are considered: recombination of electrons and holes with selection rules (Delta) u equals 0, and (Delta) u equals 1, 2, ..., where u is the level number; resonant self-effect of Fabry-Perot cavity modes field via the volume of laser crystal, layers of which, including GaAs substrate, are transparent in the 0.98 micrometers wavelength range. The latter model was confirmed experimentally.

On the possibility of the nucleation of magnetic vortices and antivortices in magnetic dielectrics using electric fields

The micromagnetic distribution in a dielectric nanoparticle is theoretically considered. It is shown that the presence of an inhomogeneous magnetoelectric interaction in magnetic dielectrics creates the possibility of nucleation of magnetic vortices and antivortices in them using an electric field. The estimation of the critical voltage necessary for vortex creation in particles of high-temperature multiferroic bismuth ferrite yields a value of ∼100 V.

Electric Field Driven Magnetic Domain Wall Motion in Iron Garnet Films

The room temperature magnetoelectric effect was observed in epitaxial iron garnet films that appeared as magnetic domain wall motion induced by electric field. The films grown on gadolinium-gallium garnet substrates with various crystallographic orientations were examined. The effect was observed in (210) and (110) films and was not observed in (111) films. Dynamic observation of the domain wall motion in 800 kV/cm electric field pulses gave the domain wall velocity in the range 30÷50 m/s. Similar velocity was achieved in magnetic field pulse about 50 Oe.

Magnetoelectrics: new type of tunable materials for microwave technique and spintronics

Multiferroics, i.e. the materials with electric and magnetic subsystems coexisting, are considered. The possible future application of materials in spintronics, storage devices and microwave technique are discussed. The results of the research devoted to the elaboration of new efficient multiferroics are presented.

Modification of the domain wall structure and generation of submicron magnetic formations by local optical irradiation

Experimental and theoretical investigations are made of the generation of vertical Bloch lines in a magnetic iron garnet film exposed to pulsed optical radiation. High-speed photography and anisotropic dark-field microscopy are used to study characteristic features of the generation of Bloch lines and domain structure relaxation processes after the local action of a laser pulse. Optimum optical irradiation parameters to ensure the controlled generation of Bloch lines are established. A theoretical model is developed which links the generation of Bloch lines to the migration of domain walls induced by local changes in the distribution of the degaussing fields caused by a reduction in magnetization with temperature at the optical radiation focusing point. The experimental results indicate that the controlled formation of magnetic structures smaller than or of the order of 0.1 μm by local optical irradiation is quite feasible.