Syktyvkar State University

The concentration dependencies of the resonance line and linewidth of ferromagnetic resonance were analyzed for two series of metal-dielectric composite films with composites CoFeB/SiO2 and CoFeZr/Zr2O3 during the work. Both series contain low CoFe alloy concentration, not exceeding 50 at.% The presence of granular and granular-percolation magnetic structures was revealed in the nanocomposite films. It was shown that the magnetic structure of composite films significantly affects the width and position of ferromagnetic resonances. The influence of metallic alloy concentration and orientation of static and alternating magnetic fields on the parameters of ferromagnetic resonance was demonstrated. In the initial position, magnetic fields lie within samples plane. It was demonstrated that the ferromagnetic resonance method is represents a structurally sensitive method for composite films investigation.

Вводятся в рассмотрение и изучаются обобщенно плотные цепи, т.е. цепи, сводящиеся определенным образом к плотным цепям. Описаны максимальные плотные подцепи произвольной цепи. Доказано, что обобщенная плотность цепи равносильна существованию в ней плотной подцепи. Выяснено строение обобщенно плотных цепей: они совпадают, с точностью до изоморфизма, с ординальными суммами обобщенно дискретных цепей по плотным цепям. Библиография: 5 названий.

The paper studies the magnetic structure, electronic spectra, magnetic and conductive properties of composite films (CoFeB + SiO2) with different metal concentrations CoFe x = 41‒75 at

The article presents the results of a study of the properties of a new pyrochlore (Bi2.7Mg0.46Ni0.70Sb2O10+Δ) using X-ray powder diffraction analysis, high-temperature X-ray powder diffraction and thermal analysis, diffuse reflectance spectroscopy, impedance spectroscopy, and X-ray spectroscopy methods (XPS, NEXAFS). The Ni/Mg codoped bismuth stibate pyrochlore was synthesized using the solid-phase method. The best results of the Rietveld structure refinement were achieved for the disordered pyrochlore model (sp. gr. Fd-3m:2, a = 10.47574(6) Å). The results of modeling the cation distribution over crystallographic positions are presented. The thermal expansion coefficient (TEC) of pyrochlore increases monotonically from 6.8 × 10−6 °C−1 (30 °C) to 9.8 × 10−6 °C−1 (810 °C). Above 1080 °C, thermal dissociation of pyrochlore occurs with the formation of (Mg/Ni)Sb2O6 and two cubic phases. At temperatures below 200 °C, the sample exhibits primarily capacitive impedance. The sample capacitance (~17 pF) is independent of temperature and frequency up to 200 °C. The high-frequency relative permittivity and dielectric loss tangent are 30.5 and 5 × 10−4 (24 °C, 5 × 104 Hz). The activation energy for conductivity is 0.99 eV. The analysis of NEXAFS and XPS spectra allowed for the determination of the charge state of the metal cations: Bi + (3-δ), Sb + (5-δ), Ni/Mg + 2.

This paper deals with the nonlinear dynamics of the magnetization vector in a ferromagnetic film with [111] hard axes orientation for magnetic and acoustic driving. The time dependencies of the magnetization components and reorientation diagrams are obtained through numerical solutions of the equations describing the motion of the magnetization vector. The characteristic appearance of the reorientation diagrams is similar for both magnetic and acoustic driving. It is observed that with acoustic driving the transition to a stable precession regime occurs faster than with magnetic excitation. The time dependencies reveal a brief transient chaotic regime at the onset of driving, followed by a transition to a stable precession regime. As the excitation force increases, complex chaotic movement of the magnetization vector begins to manifest itself, making it virtually impossible to predict its final position.