Bulletin of the Russian Academy of Sciences: Physics最新文献

The authors discuss nonlinear physical processes in end-face hysteretic electromechanical energy converters, nonsymmetric modes of their operation, and features of their mathematical modelling and calculations. A variety of power losses in converters are investigated. Recommendations are developed for using results from this work.

Maxwell’s equations without using the magnetostatic approximation were used to derive a dispersion equation for spin waves in a tangentially magnetized ferrite plate one of the surfaces of which adjoins a perfect magnetic wall, and the isofrequency dependences of these waves were calculated. It was found that the wave distribution along the plate thickness is described by two wavenumbers, and the isofrequency dependences of different modes of spin waves smoothly pass one into another and have sections corresponding to the volume–volume, volume–surface, and surface–surface wave distributions.

A multiparameter system for detecting ionizing radiation was created at the Khlopin Radium Institute to determine the composition of spent nuclear fuel to introduce it into fuel processing production cycles, in particular, to analyze the composition of liquids in hydrometallurgical conversion. The main task was to create a universal device (hardware–software complex) that can be adapted to determine the concentration of radioactive isotopes in various technological cycles by replacing detectors and/or reconfiguring software.

The OptModel resonance optical-model code is used to fit available experimental data on the elastic scattering of deuteron on ¹⁶O nuclei: differential cross section data at deuteron energies E_d of 0.98 to 200 MeV and ¹⁶O + d total reaction cross sections of 38 to 97 MeV. Violation of scattering matrix unitarity (optical-model + resonance) at several energies did not exceed 14%, which corresponds to the mean errors of the analyzed data.

A mathematical model is presented for a three-dimensional quasi-stationary electromagnetic field of secondary sources induced by an external non-sinusoidal periodic field in a conducting control object containing a closed defect. Numerical modeling of the electromagnetic field near such an object is done using software with the developed mathematical model. Results are compared to magneto-optical images of defects observed in an experiment.

The authors study frequency spectra of the dielectric/magnetic permittivity and losses of ferrospinels produced via sintering using solid-phase reactions from initial reagent [(NiCuZn)OMnO₂]Fe₂O₃. Systems of ferrites with variable signs of the temperature coefficient of magnetic saturation are considered. Such systems are of practical interest for use in devices that require impedance matching while ensuring stable magnetization in the specified temperature range (–40 to 100°C), which can vary by no more than 5%. Results from studying ferrospinels in the 1 MHz to 3 GHz range of frequencies are discussed.

A method is proposed to significantly reduce the influence of the magnetostatic magnetic field of the fixed magnetic layer on the free layer of a spin-tunnel element. The method is based on the use of a free layer the size of which exceeds that of the fixed layer, due to which a significant reduction in the influence of the magnetostatic field is achieved.

A combination of X-ray diffraction, Mössbauer spectroscopy, and measurements of magnetic characteristics are used to study the crystal structure, morphology, and magnetic properties of nanocomposite powders based on transition metals Ni, Co, Cu, and Fe, synthesized in low-temperature underwater plasma for the first time. Results demonstrate the possibility of synthesizing nanocomposites with given contents of NiFe₂O₄, CoFe₂O₄, and Ni_{1 – x}Cu_хFe₂O₄ ferrites, which ensure small ferromagnetic resonance linewidths, and ε-Fe₂O₃, which has high frequency resonance in the millimeter range of electromagnetic radiation.