M. A. Stepovich

Atomic-force microscopy of Fe3(SiAl) alloys under magnetic-pulse treatment

The influence of weak (10–100 kA/m) low-frequency (10–20 Hz) pulsed magnetic fields on the surface structure and physical and mechanical parameters of Fe3(SiAl) alloys is studied by atomic-force microscopy and porometry.

One possibility of mathematically modeling the thermal effect of a finely focused electron beam on a homogeneous semiconductor

The problem of heat distribution in materials irradiated with finely focused medium-energy electron beams is considered by means of mathematical simulation. A model is developed by solving a multidimensional heat-transfer steady equation using the Green function. A model that can be applied to a broad class of solid bodies and the range of energies of primary electrons is used as the source function. Some results are illustrated using the example of semiconductor materials used in electronics.

Effect of magnetic pulse treatment on the magnetic characteristics of yttrium–iron garnets

The effect weak (10–100 kA m–1) low-frequency (10–20 Hz) pulsed magnetic fields have on the surface structure and magnetic characteristics of yttrium–iron garnet Y3Fe5O12 is studied by means of electron and Mössbauer spectroscopy. A mechanism is proposed for the variation of saturation magnetization in Y3Fe5O12 after magnetic pulse treatment. The mechanism is associated with the change in the spin state of iron ions localized in the tetrahedral sublattice.

Effect of magnetic field pulses on the structure and properties of magnetite

The effect of weak pulsed magnetic fields on the structure and properties of magnetite is analyzed. It is found that different degrees of ordering of cations and vacancies and, consequently, iron ions facilitate the formation of its polymorphic modifications.

On some problems of modeling the distributions of minority charge carriers generated by an electron beam in a semiconductor material

The results of estimating different projection approximation schemes (a modified least-squares method and the Galerkin and Ritz methods) are presented. They are used to simulate the distribution of minority charge carriers, which is observed as a result of the diffusion of minority charge carriers generated by a broad electron beam in a homogeneous semiconductor material. Certain computational features of the implementation of the considered methods are considered.

On the possibility of using recursive trigonometric functions to calculate the distribution of nonequilibrium minority charge carriers in a two-layer semiconductor material

Some possibilities of using a new method for the continuous approximation of step functions are considered. It is based on using trigonometric expressions in the form of recursive functions. For a model of independent sources, a second-order difference scheme of approximation on a uniform mesh is constructed. This makes it possible to calculate the distribution of minority charge carriers generated by a broad electron beam in a two-layer semiconductor material.

Three-dimensional diffusion of excitons generated by an electron beam in a semiconductor material: Results of mathematical modeling

A mathematical model of three-dimensional exciton-diffusion excited by a narrow electron beam in a semiconductor material is described and studied. It is shown that the obtained model can be used to estimate the exciton-diffusion coefficient in accordance with results of experimental time-of-flight measurements for samples coated with an opaque mask with circular holes. Parameters that are characteristic for GaN are used in the simulation.

Effect of Magnetic Pulse Processing on the Structure and Magnetic Properties of Ferrites

The effect a pulsed magnetic field has on the crystal structure and macroscopic magnetic parameters of hexagonal ferrites BaFe12O19 and SrFe12O19 are studied. It is shown that changes in the physical properties of ferrites are due to the ordering of cation vacancies on the boundaries of hexagonal and spinel blocks that minimize local distortion of the oxygen polyhedrons. Violation of the collinear ordering of the magnetic moments of iron ions in the nonequivalent positions of SrFe12O19 ferrite is observed, due to the selective localization of such vacancies (and thus violations of the magnetic relationships in Fe–O–Fe).

Investigation of the local characteristics of amorphous electrical steel

The local characteristics of amorphous electrical steel (foil) before and after exposure to weak (10–100 kA/m) low-frequency (10–20 Hz) magnetic-field pulses are studied by atomic force microscopy, scanning electron microscopy, and electron probe microanalysis. The research results show that, at certain magnetic-treatment parameters, the magnetic properties of the material change, while the concentrations of the phases present in it and the surface structure of the foil remain unchanged.

Modifying the properties of ferrite materials with a hexagonal structure via treatment in corona discharge plasma

The influence of treatment in corona discharge plasma on the magnetic properties of BaFe12O19 single- and polycrystalline ferrites, as well as structural-chemical transformations in their crystal lattices, are studied. The revealed dependence between structural-sensitive microscopic parameters and the duration of corona-discharge-plasma treatment indicates the manifestation of the corona-electret effect in BaFe12O19 single crystals.