Magnetization Dynamics in Two-Dimensional Arrays of Square Microelements

The collective magnetization motion in an array of magnetostatically interacting ferromagnetic square elements is studied theoretically and experimentally. Dispersion laws are obtained for collective modes for some particular cases of the distribution of the topological charges π _T of magnetic vortices in particles. Resonance curves are plotted with allowance for dissipation for various values of π _T . An experimental investigation of the ferromagnetic resonance in a two-dimensional array of particles qualitatively supports the calculation results.     

Collective motion of magnetization in two-dimensional arrays of square elements

The resonance in a two-dimensional array of square ferromagnetic elements has been experimentally investigated. The magnetization of the elements is shown to be in the vortex state. The resonance peak splitting in the array with increasing density of the elements has been established. The explanation of this phenomenon is proposed and eigenfrequencies of the collective modes are theoretically estimated. Different combinations of polarities and chiralities of the nearest elements in the array are examined.     

Instability of a tubular electron beam moving over a dielectric cylinder

The mechanism of interactions between the eigenwaves of a dielectric cylinder and a nonrelativistic tubular electron beam moving over its surface has been considered theoretically. A dispersion relation for the coupled waves of beam electrons and the dielectric cylinder has been derived. The conditions for coupled wave instability have been formulated and an expression for instability increments has been found. It follows from the dispersion relation and the expression for the increments that electric waves with high azimuthal indices are excited most effectively at a narrow gap between the beam and cylinder.     

Distribution of the Field of Whispering-Gallery Modes in a Radially Nonuniform Two-Layer Cylindrical Dielectric Resonator

We study eigenmodes of a radially nonuniform two-layer cylindrical dielectric resonator bounded by two perfectly conducting planes at its ends. Formulas for the electromagnetic-field components of the modes and the characteristic equation of the resonator made of anisotropic dielectrics and immersed in an anisotropic medium are obtained. Resonators with various whispering-gallery modes are studied numerically in the 8-mm wavelength range. The distributions of the axial field component of the eigenmodes over the radial coordinate are given for various values of the radius, dielectric permittivity, and loss tangent of the inner layer of the resonator. The influence of the inner-layer parameters on the behavior of field distribution over the radius and on the spectral and energy characteristics of the resonator are analyzed. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 7, pp. 622–632, July 2008.     

Temperature-dielectric spectroscopy of aqueous solutions using the method of capillary-waveguide resonance

We study the temperature dependences of the frequency characteristics of a capillary-waveguide resonator for strongly absorbing media. The temperature influence on the frequency, Q-factor, and absorption depth in the studied resonance is theoretically revealed and experimentally confirmed. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 8, pp. 711–716, August 2008.