A solution is found to the self-consistent system of equations describing the motion and bending ... more A solution is found to the self-consistent system of equations describing the motion and bending of domain walls on experiencing a fluctuating external magnetic field. The electromagnetic loss rate in conductive ferromagnetic materials is calculated for the case where the walls bend only slightly and inductions are fairly low. In the range of comparatively low frequencies this rate is less than that calculated on the basis of flat wall representations. The manner of bending is analyzed and in the low-frequency range it is found to be due mainly to phase shifts of different points of a wall about one another. The resonance energy absorption of an external HF magnetic field is examined in conductive materials with domain walls. It is shown that a uniform external high-frequency field may excite three types of wall vibrations, because the vertical field in the material is non-uniform. The resonance frequencies at which these vibrations should be excited have been found, and the widths ...
ABSTRACT A general approach to the synthesis of optimal magnet systems (MS) from hard magnets and... more ABSTRACT A general approach to the synthesis of optimal magnet systems (MS) from hard magnets and soft magnetic elements has been described. Using the developed approach axially symmetric MS with optimal mass and size characteristics for microwave electronics and NMR application have been design.
Sedimentation dynamics of magnetite (γ-Fe3O4) nanopowder (10-20 nm) in water in a gradient magnet... more Sedimentation dynamics of magnetite (γ-Fe3O4) nanopowder (10-20 nm) in water in a gradient magnetic field Bmax = 0.3 T, (dB/dz)max = 0.13 T/cm was studied for different water flow speeds and starting particle concentrations (0.1 and 1.0 g/l). The aggregates formation in water was monitored under the same conditions. In cyclical water flow, the velocity of particle sedimentation increases significantly in comparison to its rate in still water, which corresponds to the intensified aggregate formation. However, at a water flow speed more than 0.1 cm/s sedimentation velocity slows down, which might be connected to aggregate destruction in a faster water flow. Correlation between sedimentation time and the nanoparticle concentration in water does not follow the trend expected for spherical superparamagnetic particles. In our case sedimentation time is shorter for c = 0.1 g/l in comparison with that for c = 1 g/l. We submit that such a feature is caused by particle self-organization in water into complex structures of fractal type. This effect is unexplained in the framework of existing theoretical models of colloids systems, so far. Provisional recommendations are suggested for the design of a magnetic separator on the permanent magnets base. The main device parameters are magnetic field intensity B ≥ 0.1 T, magnetic field gradient (dB/dz)max ≈ (0.1-0.2) T/cm, and water flow speed V < 0.15 cm/s. For particle concentration c = 1 g/l, purification of water from magnetite down to ecological and hygienic standards is reached in 80 min, for c = 0.1 g/l the time is reduced down to 50 min.
Characteristics of a compact relativistic backward wave oscillator (BWO) operating in the 8-mm wa... more Characteristics of a compact relativistic backward wave oscillator (BWO) operating in the 8-mm wavelength range have been optimized using the results of experimental investigation and numerical simulations. The coefficient of electron beam power conversion into microwave pulses close to unity is obtained for electrons transported in inhomogeneous magnetic field (2.2–1.7 T) below the cyclotron resonance level. In a regime of
ABSTRACT The dynamics of a system of domain walls has been considered in finite samples of a rect... more ABSTRACT The dynamics of a system of domain walls has been considered in finite samples of a rectangular or a trapezoid (wedge) shape. Based on the solution to the set of equations of motion for the system of domain walls, it has been shown that the equilibrium positions and amplitudes of vibrations of domain walls are determined by the magnetostatic field caused by the sample shape. The role of possible physical mechanisms controlling the translational motion of the domain structure is discussed.
A solution is found to the self-consistent system of equations describing the motion and bending ... more A solution is found to the self-consistent system of equations describing the motion and bending of domain walls on experiencing a fluctuating external magnetic field. The electromagnetic loss rate in conductive ferromagnetic materials is calculated for the case where the walls bend only slightly and inductions are fairly low. In the range of comparatively low frequencies this rate is less than that calculated on the basis of flat wall representations. The manner of bending is analyzed and in the low-frequency range it is found to be due mainly to phase shifts of different points of a wall about one another. The resonance energy absorption of an external HF magnetic field is examined in conductive materials with domain walls. It is shown that a uniform external high-frequency field may excite three types of wall vibrations, because the vertical field in the material is non-uniform. The resonance frequencies at which these vibrations should be excited have been found, and the widths ...
ABSTRACT A general approach to the synthesis of optimal magnet systems (MS) from hard magnets and... more ABSTRACT A general approach to the synthesis of optimal magnet systems (MS) from hard magnets and soft magnetic elements has been described. Using the developed approach axially symmetric MS with optimal mass and size characteristics for microwave electronics and NMR application have been design.
Sedimentation dynamics of magnetite (γ-Fe3O4) nanopowder (10-20 nm) in water in a gradient magnet... more Sedimentation dynamics of magnetite (γ-Fe3O4) nanopowder (10-20 nm) in water in a gradient magnetic field Bmax = 0.3 T, (dB/dz)max = 0.13 T/cm was studied for different water flow speeds and starting particle concentrations (0.1 and 1.0 g/l). The aggregates formation in water was monitored under the same conditions. In cyclical water flow, the velocity of particle sedimentation increases significantly in comparison to its rate in still water, which corresponds to the intensified aggregate formation. However, at a water flow speed more than 0.1 cm/s sedimentation velocity slows down, which might be connected to aggregate destruction in a faster water flow. Correlation between sedimentation time and the nanoparticle concentration in water does not follow the trend expected for spherical superparamagnetic particles. In our case sedimentation time is shorter for c = 0.1 g/l in comparison with that for c = 1 g/l. We submit that such a feature is caused by particle self-organization in water into complex structures of fractal type. This effect is unexplained in the framework of existing theoretical models of colloids systems, so far. Provisional recommendations are suggested for the design of a magnetic separator on the permanent magnets base. The main device parameters are magnetic field intensity B ≥ 0.1 T, magnetic field gradient (dB/dz)max ≈ (0.1-0.2) T/cm, and water flow speed V < 0.15 cm/s. For particle concentration c = 1 g/l, purification of water from magnetite down to ecological and hygienic standards is reached in 80 min, for c = 0.1 g/l the time is reduced down to 50 min.
Characteristics of a compact relativistic backward wave oscillator (BWO) operating in the 8-mm wa... more Characteristics of a compact relativistic backward wave oscillator (BWO) operating in the 8-mm wavelength range have been optimized using the results of experimental investigation and numerical simulations. The coefficient of electron beam power conversion into microwave pulses close to unity is obtained for electrons transported in inhomogeneous magnetic field (2.2–1.7 T) below the cyclotron resonance level. In a regime of
ABSTRACT The dynamics of a system of domain walls has been considered in finite samples of a rect... more ABSTRACT The dynamics of a system of domain walls has been considered in finite samples of a rectangular or a trapezoid (wedge) shape. Based on the solution to the set of equations of motion for the system of domain walls, it has been shown that the equilibrium positions and amplitudes of vibrations of domain walls are determined by the magnetostatic field caused by the sample shape. The role of possible physical mechanisms controlling the translational motion of the domain structure is discussed.
Uploads
Papers by Sergey Zhakov